Background:

This study examined the incidence and correlates of cancer among homeless and unstably housed (HUH) veterans as compared with stably housed (SH) veterans.

Methods:

Using Veterans Affairs (VA) administrative data from 564,563 HUH and 5,213,820 SH veterans in 2013 and 2014, we examined the types and stages of 69 different types of cancer diagnosed among HUH and SH veterans. Sociodemographic and psychiatric characteristics associated with cancer were also examined.

Results:

The 1-year incidence rate of cancer was 21.5% lower among HUH veterans than SH veterans (0.68% and 0.86%, respectively). There was no difference in the most common stages and types of cancer among HUH and SH veterans. The most common primary sites of cancer were in the prostate, lung, and bronchus. HUH veterans were more likely than SH veterans to have cancer of the liver and intrahepatic bile ducts (∆4.79%). Among HUH veterans, older age and alcohol use disorder were associated with greater risk for any incident cancer while suicidal ideation/behaviors were associated with lower risk. Psychiatric conditions were often diagnosed before cancer diagnosis for SH and HUH veterans; rates of substance use disorders and suicidal ideation/behaviors decreased in HUH veterans after cancer diagnosis.

Conclusions:

The VA health care system serves many HUH veterans with cancer. Mental health and substance use disorders are important to treat in veterans at risk of cancer and as potential sequalae of cancer.

Impact:

The high prevalence of psychiatric disorders in HUH populations is important to consider in the diagnosis and treatment of cancer in these populations.

Although cancer is the second leading cause of death in the United States (1), there has been inadequate study of cancer in homeless populations. The few U.S. studies that exist have found higher rates of cancer and cancer-related deaths among homeless adults compared with adults in the general population (2–4). This may be due to various socioeconomic and health risk factors, such as poverty, poor mental health, addiction, and chronic medical conditions found in homeless populations (5, 6). In addition, homeless adults often face barriers to health care and preventive services which can affect their rates of cancer screening, and access and use of cancer treatment (7, 8).

The U.S. Department of Veterans Affairs (VA) operates the largest integrated health care system in the United States and veterans are considered an important segment of the U.S. population comprising about 7% of U.S. adults (9). Addressing the health and social needs of homeless and unstably housed (HUH) veterans has been a federal priority for over a decade and considerable resources have been dedicated toward achieving the goal of preventing and ending veteran homelessness (10–12). While much programming and research have been dedicated to housing and mental health needs, less attention has been paid to needs around primary care and specialty medical care, including cancer screening and treatment of cancer in this population.

Unlike other health care systems in the United States, veterans who are enrolled in VA health care have access to comprehensive services and do not need to rely on particular insurance coverage for access to services (13); this is true for HUH veterans as well. The most recent comprehensive description of cancer incidence among veterans reported that in 2007, 97.5% of cancer diagnosed in VA were men, 79% were White, and the median age at diagnosis was 66 years old (14). Cancer incidence among male veterans largely mirrored that of the general U.S. male population. The five most commonly diagnosed cancers were similar between VA and the U.S. male population, being prostate (32%), lung/bronchus (18.8%), colon/rectum (8.6%), urinary bladder (3.6%), and skin melanomas (3.4%). It is unknown whether the elevated cancer rates observed between HUH and general adult populations extends to HUH veterans and stably housed (SH) veterans in the VA health care system who have access to various services including cancer screening and care.

To address this knowledge gap, this study conducted an epidemiologic examination using national VA data to compare the incidence of different types and stages of cancer among HUH and SH veterans. Furthermore, analyses were conducted to identify sociodemographic and psychiatric factors associated with any cancer among HUH and SH veterans.

Cancer data for this study were extracted from the VA's Corporate Data Warehouse (CDW) Oncology domain, which consists of raw data abstracted at the local level by tumor registrars and subsequently used by the VA Central Cancer Registry (VACCR) to create finalized annual datasets. Per recommended practices to attain quality data consistent with the VACCR (15), we used the raw data and restricted our analyses to cases with complete abstract status. We further excluded in situ cancers, limiting our analyses to invasive neoplasms. Primary anatomic site was defined according to International Classification of Diseases for Oncology (ICD-O-3) codes.

To assess cancer incidence among HUH and SH veterans, we used data from 2013 and 2014 to create a cohort of HUH and SH veterans. We selected these years of data because they were the most recent for which the total number of cancer cases was comparable with those provided in a previous article using 2007 and 2010 VACCR data (14). Per standard practice (16), we identified as HUH any veteran who had an ICD-10 code Z59.0, participated in any VA homeless program, or screened positive for homelessness or risk of homelessness on the VA homeless risk screening clinical reminder. Veterans who screened negative for both homelessness and risk of homelessness were presumed to be SH. Our sample consisted of 564,563 HUH veterans and 5,213,820 SH veterans. For each veteran in our cohort, the index date was the date of the earliest HUH indicator or negative screen between January 1, 2013 and December 31, 2014.

We used a 1-year term following the index date to extract cancer diagnoses from the CDW Oncology domain, and psychiatric diagnoses from CDW inpatient and outpatient medical records. Sociodemographic data were also extracted from the CDW. Thus, we used a combined 2 years of data to include a large sample of veterans but we only followed each veteran for 1 year and based that 1 year on their index date.

To categorize and examine stages of cancer, we used the Surveillance, Epidemiology, and End Results (SEER) Summary Stage which categorizes how far a cancer has spread from its point of origin in one of six main categories, which includes localized, regional by direct extension, regional to lymph nodes, regional by extension and to nodes, regional not otherwise specified, and metastasis/systemic disease (RRID:SCR_006902). SEER Summary Stages were used because it is the most basic approach to categorizing cancer progress and is more general in its categorization which allows for more direct comparison across cancer types. We also examined the primary site of the cancer as recorded in the CDW Oncology domain.

Data analysis

Epidemiologic descriptive analyses were conducted to describe the overall incidence rate of cancer, different stages of cancer, and different types of cancer among HUH and SH veterans. Given the large sample sizes rendering even tiny differences significant, we opted to calculate differences in proportions as an effect size measure. A series of logistic regressions was then conducted. First, a logistic regression was conducted with the total sample to examine whether HUH veterans were at greater risk of incident cancer than SH veterans, adjusting for sociodemographic and psychiatric factors (i.e., age, gender, race/ethnicity, marital status, VA service-connected disability, combat exposure, military sexual trauma, mental health and substance use disorder diagnoses, and any suicidal ideation/behaviors). Second, two additional logistic regression analyses were conducted to examine how these sociodemographic and psychiatric factors were associated with any incidence of cancer among SH veterans and HUH veterans separately. In regression analyses, cases with missing data were excluded by listwise deletion except for cases that were only missing race/ethnicity because they constituted 10% to 13% of cases. ORs were calculated along with 95% confidence intervals (CI). And third, a supplementary analysis was conducted using descriptive statistics with the total sample to determine whether psychiatric conditions often preceded or followed cancer diagnoses.

Data availability

Data from this study are available upon request from the first author who can provide information about the required procedures needed to be taken to obtain access to VA data.

Table 1 shows background characteristics and the incidence rate of cancer among HUH and SH veterans. The overall 1-year cancer incidence rate of HUH veterans was 0.68% (3,825/564,563) compared with 0.86% among SH veterans (45,019/5,213,820), which is a 0.19% difference or 21.5% lower rate of cancer incidence among HUH veterans as compared with SH veterans.

Table 1.

Sociodemographic and psychiatric characteristics of SH and HUH veterans.

SH veteransHUH veterans
(N = 5,213,820)(N = 564,563)
VariableN%N%Δ%
Age 
 17–29 238,542 4.6% 43,912 7.8% −3.2% 
 30–39 359,749 6.9% 73,814 13.1% −6.2% 
 40–49 449,325 8.6% 80,845 14.3% −5.7% 
 50–59 720,262 13.8% 168,290 29.8% −16.0% 
 60–69 1,652,473 31.7% 115,177 20.4% 11.3% 
 70–79 849,867 16.3% 27,055 4.8% 11.5% 
 80+ 750,934 14.4% 9,773 1.7% 12.7% 
 Missing 192,668 3.7% 45,697 8.1% −4.4% 
Sex 
 Male 4,665,460 89.5% 460,500 81.6% 7.9% 
 Female 355,521 6.8% 57,973 10.3% −3.4% 
 Missing 192,839 3.7% 46,090 8.2% −4.5% 
Race/ethnicity 
 Non-Hispanic White 3,559,812 68.3% 261,662 46.3% 21.9% 
 Non-Hispanic Black 717,967 13.8% 174,271 30.9% −17.1% 
 Hispanic 287,670 5.5% 37,384 6.6% −1.1% 
 Mixed race/other 144,400 2.8% 19,919 3.5% −0.8% 
 Missing 503,971 9.7% 71,327 12.6% −3.0% 
Marital status 
 Married 2,909,826 55.8% 121,075 21.4% 34.4% 
 Single/never married 557,736 10.7% 136,192 24.1% −13.4% 
 Divorced/separated 1,167,999 22.4% 237,669 42.1% −19.7% 
 Widowed 343,534 6.6% 17,670 3.1% 3.5% 
 Missing 234,725 4.5% 51,957 9.2% −4.7% 
VA service connection % 
 None/0% 2,216,659 42.5% 229,503 40.7% 1.9% 
 10%–40% 880,122 16.9% 84,155 14.9% 2.0% 
 50%–100% 1,924,941 36.9% 205,274 36.4% 0.6% 
 Missing 192,098 3.7% 45,631 8.1% −4.4% 
Combat exposure 711,812 13.7% 63,183 11.2% 2.5% 
Military sexual trauma 175,299 3.4% 52,657 9.3% −6.0% 
One-year incidence of any cancer 45,019 0.86% 3,825 0.68% 0.2% 
SH veteransHUH veterans
(N = 5,213,820)(N = 564,563)
VariableN%N%Δ%
Age 
 17–29 238,542 4.6% 43,912 7.8% −3.2% 
 30–39 359,749 6.9% 73,814 13.1% −6.2% 
 40–49 449,325 8.6% 80,845 14.3% −5.7% 
 50–59 720,262 13.8% 168,290 29.8% −16.0% 
 60–69 1,652,473 31.7% 115,177 20.4% 11.3% 
 70–79 849,867 16.3% 27,055 4.8% 11.5% 
 80+ 750,934 14.4% 9,773 1.7% 12.7% 
 Missing 192,668 3.7% 45,697 8.1% −4.4% 
Sex 
 Male 4,665,460 89.5% 460,500 81.6% 7.9% 
 Female 355,521 6.8% 57,973 10.3% −3.4% 
 Missing 192,839 3.7% 46,090 8.2% −4.5% 
Race/ethnicity 
 Non-Hispanic White 3,559,812 68.3% 261,662 46.3% 21.9% 
 Non-Hispanic Black 717,967 13.8% 174,271 30.9% −17.1% 
 Hispanic 287,670 5.5% 37,384 6.6% −1.1% 
 Mixed race/other 144,400 2.8% 19,919 3.5% −0.8% 
 Missing 503,971 9.7% 71,327 12.6% −3.0% 
Marital status 
 Married 2,909,826 55.8% 121,075 21.4% 34.4% 
 Single/never married 557,736 10.7% 136,192 24.1% −13.4% 
 Divorced/separated 1,167,999 22.4% 237,669 42.1% −19.7% 
 Widowed 343,534 6.6% 17,670 3.1% 3.5% 
 Missing 234,725 4.5% 51,957 9.2% −4.7% 
VA service connection % 
 None/0% 2,216,659 42.5% 229,503 40.7% 1.9% 
 10%–40% 880,122 16.9% 84,155 14.9% 2.0% 
 50%–100% 1,924,941 36.9% 205,274 36.4% 0.6% 
 Missing 192,098 3.7% 45,631 8.1% −4.4% 
Combat exposure 711,812 13.7% 63,183 11.2% 2.5% 
Military sexual trauma 175,299 3.4% 52,657 9.3% −6.0% 
One-year incidence of any cancer 45,019 0.86% 3,825 0.68% 0.2% 

Note: VA service connection is set in 10% intervals.

As shown in Table 2, the majority of incident cancer for both HUH and SH veterans was in the “localized” SEER summary stage (50.3% vs. 51.6%) followed by the “metastasis/systemic disease” stage (24.1% vs. 21.6%) which only differed by 1.1%. There was no notable difference (<Δ1.0%) on other SEER summary stages of cancer between HUH and SH veterans.

Table 2.

SEER summary stage of cancer among SH compared with HUH veterans, 2013 and 2014.

SHHUH
SEER summary stage (2000)N%N%Δ%
 Unknown 2,278 4.6% 197 4.9% −0.3% 
Localized 25,029 50.3% 2,096 51.6% −1.3% 
Regional by direct extension 3,852 7.7% 344 8.5% −0.7% 
Regional to lymph nodes 3,166 6.4% 292 7.2% −0.8% 
Regional by extension and to nodes 2,954 5.9% 213 5.2% 0.7% 
Regional NOS 488 1.0% 42 1.0% −0.1% 
Metastasis/systemic disease 11,982 24.1% 877 21.6% 2.5% 
 Total 49,749  4,061   
SHHUH
SEER summary stage (2000)N%N%Δ%
 Unknown 2,278 4.6% 197 4.9% −0.3% 
Localized 25,029 50.3% 2,096 51.6% −1.3% 
Regional by direct extension 3,852 7.7% 344 8.5% −0.7% 
Regional to lymph nodes 3,166 6.4% 292 7.2% −0.8% 
Regional by extension and to nodes 2,954 5.9% 213 5.2% 0.7% 
Regional NOS 488 1.0% 42 1.0% −0.1% 
Metastasis/systemic disease 11,982 24.1% 877 21.6% 2.5% 
 Total 49,749  4,061   

Abbreviations: NOS, not otherwise specified; SEER, Surveillance, Epidemiology, and End Results.

Table 3 shows the incidence of different types of cancer between HUH and SH veterans. The most common primary site of cancer among both HUH and SH veterans was in the prostate, followed by the lung and bronchus. Following these primary sites, there were some differences in other common primary sites of cancer between HUH and SH veterans. Among HUH veterans, the most common primary sites of cancer after prostate and lung and bronchus were, in order, liver and intrahepatic bile ducts, hematopoietic and reticuloendothelial systems, kidney, colon, and melanoma of skin. Among SH veterans, they were hematopoietic and reticuloendothelial systems, melanoma of skin, colon, kidney, and liver and intrahepatic bile ducts (in order). Among the largest differences between HUH and SH veterans, HUH veterans had a higher incidence of cancer of the liver and intrahepatic bile ducts than SH veterans (Δ5.21%); conversely, SH veterans had higher incidence of cancer of the hematopoietic and reticuloendothelial systems (Δ2.00%), bronchus and lung (Δ 1.72%), bladder (Δ1.45%), and melanoma of skin (Δ1.72%) than HUH veterans.

Table 3.

Primary site of cancer among SH compared with HUH veterans, 2013 and 2014.

SHHUH
Primary siteN%N%Δ%
Lip, oral cavity & pharynx 
 C00 Lip 157 0.32% 0.20% 0.12% 
 C01 Base of tongue 458 0.92% 39 0.96% −0.04% 
 C02 Other/NOS parts of tongue 231 0.46% 18 0.44% 0.02% 
 C03 Gum 35 0.07% 0.05% 0.02% 
 C04 Floor of mouth 155 0.31% 17 0.42% −0.11% 
 C05 Palate 99 0.20% 11 0.27% −0.07% 
 C06 Other/NOS parts of mouth 76 0.15% 13 0.32% −0.17% 
 C07 Parotid gland 120 0.24% 16 0.39% −0.15% 
 C08 Other/NOS major salivary glands 17 0.03% 0.07% −0.04% 
 C09 Tonsil 515 1.04% 47 1.16% −0.12% 
 C10 Oropharynx 126 0.25% 10 0.25% 0.01% 
 C11 Nasopharynx 72 0.14% 11 0.27% −0.13% 
 C12 Pyriform sinus 88 0.18% 12 0.30% −0.12% 
 C13 Hypopharynx 80 0.16% 13 0.32% −0.16% 
 C14 Other/ill-defined sites in lip, oral cavity, and pharynx 49 0.10% 0.07% 0.02% 
Digestive organs 
 C15 Esophagus 975 1.96% 67 1.65% 0.31% 
 C16 Stomach 765 1.54% 64 1.58% −0.04% 
 C17 Small intestine 246 0.49% 15 0.37% 0.13% 
 C18 Colon 2,587 5.20% 173 4.26% 0.94% 
 C19 Rectosigmoid junction 221 0.44% 23 0.57% −0.12% 
 C20 Rectum 1,001 2.01% 113 2.78% −0.77% 
 C21Anus and anal canal 154 0.31% 20 0.49% −0.18% 
 C22 Liver and intrahepatic bile ducts 2,052 4.12% 379 9.33% −5.21% 
 C23 Gallbladder 50 0.10% 0.05% 0.05% 
 C24 Other/NOS parts of biliary tract 149 0.30% 0.22% 0.08% 
 C25 Pancreas 1,152 2.32% 92 2.27% 0.05% 
 C26 Other/ill-defined digestive organs 27 0.05% 0.02% 0.03% 
Respiratory and intrathoracic organs 
 C30 Nasal cavity and middle ear 50 0.10% 0.17% −0.07% 
 C31 Accessory sinuses 28 0.06% 0.02% 0.03% 
 C32 Larynx 930 1.87% 71 1.75% 0.12% 
 C33 Trachea 0.02% 0.00% 0.02% 
 C34 Bronchus and lung 9,150 18.39% 677 16.67% 1.72% 
 C37 Thymus 31 0.06% 0.15% −0.09% 
 C38 Heart, mediastinum, and pleura 122 0.25% 0.15% 0.10% 
Bones and articular cartilage  0.00%  0.00% 0.00% 
 C40 Bones and articular cartilage - limbs 10 0.02% 0.00% 0.02% 
 C41 Bones and articular cartilage - other/NOS 47 0.09% 0.20% −0.10% 
Hematopoietic and endothelial systems (leukemias) 
 C42 Hematopoietic and reticuloendothelial systems 3,397 6.83% 196 4.83% 2.00% 
Skin 
 C43 Melanoma of skin 2,593 5.21% 156 3.84% 1.37% 
 C44 Other/NOS malignant neoplasm of skin 0.01% 0.02% −0.02% 
Mesothelial and soft tissue      
 C47 Peripheral nerves and autonomic nervous system 11 0.02% 0.00% 0.02% 
 C48 Retroperitoneum and peritoneum 42 0.08% 0.07% 0.01% 
 C49 Other connective and soft tissue 315 0.63% 23 0.57% 0.07% 
Breast and female genital organs 
 C50 Breast 584 1.17% 57 1.40% −0.23% 
 C51 Vulva 13 0.03% 0.00% 0.03% 
 C52 Vagina 0.00% 0.02% −0.02% 
 C53 Cervix uteri 30 0.06% 0.07% −0.01% 
 C54 Corpus gland 78 0.16% 11 0.27% −0.11% 
 C55 Uterus NOS 0.00% 0.02% −0.02% 
 C56 Ovary 17 0.03% 0.10% −0.06% 
 C57 Other/NOS female genital organs 0.00% 0.02% −0.02% 
Male genital organs 
 C60 Penis 94 0.19% 0.17% 0.02% 
 C61 Prostate 12,640 25.41% 1,067 26.27% −0.87% 
 C62 Testis 150 0.30% 18 0.44% −0.14% 
 C63 Other/NOS male genital organs 14 0.03% 0.05% −0.02% 
Urinary tract 
 C64 Kidney 2,226 4.47% 190 4.68% −0.20% 
 C65 Renal pelvis 103 0.21% 0.17% 0.03% 
 C66 Ureter 85 0.17% 0.10% 0.07% 
 C67 Bladder 1,920 3.86% 98 2.41% 1.45% 
 C68 Other/NOS urinary organs 38 0.08% 0.00% 0.08% 
Eye, brain, and other parts of CNS 
 C69 Eye/adnexa 47 0.09% 0.07% 0.02% 
 C70 Meninges 74 0.15% 14 0.34% −0.20% 
 C71 Brain 328 0.66% 24 0.59% 0.07% 
 C72 Spinal cord, cranial nerves, and other parts of CNS 36 0.07% 0.10% −0.03% 
Thyroid and other endocrine glands 
 C73 Thyroid gland 583 1.17% 49 1.21% −0.03% 
 C74 Adrenal gland 13 0.03% 0.10% −0.07% 
 C75 Other endocrine glands and related structures 86 0.17% 10 0.25% −0.07% 
Other and ill-defined sites 
 C76 Other and ill-defined sites 56 0.11% 0.02% 0.09% 
 C77 Secondary and unspecified malignant neoplasm of lymph nodes 1,292 2.60% 87 2.14% 0.45% 
 C80 Unspecified 843 1.69% 58 1.43% 0.27% 
Total 49,749  4,061   
SHHUH
Primary siteN%N%Δ%
Lip, oral cavity & pharynx 
 C00 Lip 157 0.32% 0.20% 0.12% 
 C01 Base of tongue 458 0.92% 39 0.96% −0.04% 
 C02 Other/NOS parts of tongue 231 0.46% 18 0.44% 0.02% 
 C03 Gum 35 0.07% 0.05% 0.02% 
 C04 Floor of mouth 155 0.31% 17 0.42% −0.11% 
 C05 Palate 99 0.20% 11 0.27% −0.07% 
 C06 Other/NOS parts of mouth 76 0.15% 13 0.32% −0.17% 
 C07 Parotid gland 120 0.24% 16 0.39% −0.15% 
 C08 Other/NOS major salivary glands 17 0.03% 0.07% −0.04% 
 C09 Tonsil 515 1.04% 47 1.16% −0.12% 
 C10 Oropharynx 126 0.25% 10 0.25% 0.01% 
 C11 Nasopharynx 72 0.14% 11 0.27% −0.13% 
 C12 Pyriform sinus 88 0.18% 12 0.30% −0.12% 
 C13 Hypopharynx 80 0.16% 13 0.32% −0.16% 
 C14 Other/ill-defined sites in lip, oral cavity, and pharynx 49 0.10% 0.07% 0.02% 
Digestive organs 
 C15 Esophagus 975 1.96% 67 1.65% 0.31% 
 C16 Stomach 765 1.54% 64 1.58% −0.04% 
 C17 Small intestine 246 0.49% 15 0.37% 0.13% 
 C18 Colon 2,587 5.20% 173 4.26% 0.94% 
 C19 Rectosigmoid junction 221 0.44% 23 0.57% −0.12% 
 C20 Rectum 1,001 2.01% 113 2.78% −0.77% 
 C21Anus and anal canal 154 0.31% 20 0.49% −0.18% 
 C22 Liver and intrahepatic bile ducts 2,052 4.12% 379 9.33% −5.21% 
 C23 Gallbladder 50 0.10% 0.05% 0.05% 
 C24 Other/NOS parts of biliary tract 149 0.30% 0.22% 0.08% 
 C25 Pancreas 1,152 2.32% 92 2.27% 0.05% 
 C26 Other/ill-defined digestive organs 27 0.05% 0.02% 0.03% 
Respiratory and intrathoracic organs 
 C30 Nasal cavity and middle ear 50 0.10% 0.17% −0.07% 
 C31 Accessory sinuses 28 0.06% 0.02% 0.03% 
 C32 Larynx 930 1.87% 71 1.75% 0.12% 
 C33 Trachea 0.02% 0.00% 0.02% 
 C34 Bronchus and lung 9,150 18.39% 677 16.67% 1.72% 
 C37 Thymus 31 0.06% 0.15% −0.09% 
 C38 Heart, mediastinum, and pleura 122 0.25% 0.15% 0.10% 
Bones and articular cartilage  0.00%  0.00% 0.00% 
 C40 Bones and articular cartilage - limbs 10 0.02% 0.00% 0.02% 
 C41 Bones and articular cartilage - other/NOS 47 0.09% 0.20% −0.10% 
Hematopoietic and endothelial systems (leukemias) 
 C42 Hematopoietic and reticuloendothelial systems 3,397 6.83% 196 4.83% 2.00% 
Skin 
 C43 Melanoma of skin 2,593 5.21% 156 3.84% 1.37% 
 C44 Other/NOS malignant neoplasm of skin 0.01% 0.02% −0.02% 
Mesothelial and soft tissue      
 C47 Peripheral nerves and autonomic nervous system 11 0.02% 0.00% 0.02% 
 C48 Retroperitoneum and peritoneum 42 0.08% 0.07% 0.01% 
 C49 Other connective and soft tissue 315 0.63% 23 0.57% 0.07% 
Breast and female genital organs 
 C50 Breast 584 1.17% 57 1.40% −0.23% 
 C51 Vulva 13 0.03% 0.00% 0.03% 
 C52 Vagina 0.00% 0.02% −0.02% 
 C53 Cervix uteri 30 0.06% 0.07% −0.01% 
 C54 Corpus gland 78 0.16% 11 0.27% −0.11% 
 C55 Uterus NOS 0.00% 0.02% −0.02% 
 C56 Ovary 17 0.03% 0.10% −0.06% 
 C57 Other/NOS female genital organs 0.00% 0.02% −0.02% 
Male genital organs 
 C60 Penis 94 0.19% 0.17% 0.02% 
 C61 Prostate 12,640 25.41% 1,067 26.27% −0.87% 
 C62 Testis 150 0.30% 18 0.44% −0.14% 
 C63 Other/NOS male genital organs 14 0.03% 0.05% −0.02% 
Urinary tract 
 C64 Kidney 2,226 4.47% 190 4.68% −0.20% 
 C65 Renal pelvis 103 0.21% 0.17% 0.03% 
 C66 Ureter 85 0.17% 0.10% 0.07% 
 C67 Bladder 1,920 3.86% 98 2.41% 1.45% 
 C68 Other/NOS urinary organs 38 0.08% 0.00% 0.08% 
Eye, brain, and other parts of CNS 
 C69 Eye/adnexa 47 0.09% 0.07% 0.02% 
 C70 Meninges 74 0.15% 14 0.34% −0.20% 
 C71 Brain 328 0.66% 24 0.59% 0.07% 
 C72 Spinal cord, cranial nerves, and other parts of CNS 36 0.07% 0.10% −0.03% 
Thyroid and other endocrine glands 
 C73 Thyroid gland 583 1.17% 49 1.21% −0.03% 
 C74 Adrenal gland 13 0.03% 0.10% −0.07% 
 C75 Other endocrine glands and related structures 86 0.17% 10 0.25% −0.07% 
Other and ill-defined sites 
 C76 Other and ill-defined sites 56 0.11% 0.02% 0.09% 
 C77 Secondary and unspecified malignant neoplasm of lymph nodes 1,292 2.60% 87 2.14% 0.45% 
 C80 Unspecified 843 1.69% 58 1.43% 0.27% 
Total 49,749  4,061   

Abbreviation: NOS, not otherwise specified.

A logistic regression of the total sample found that HUH veterans were at lower risk of incident cancer than SH veterans (OR = 0.63; 95% CI = 0.60–0.65; P < 0.001) controlling for sociodemographic and psychiatric factors. Table 4 shows two logistic regression analyses that were then conducted to examine sociodemographic and psychiatric factors associated with any incident cancer among SH veterans and HUH veterans separately. Among SH veterans, the largest ORs (ORs ≥1.50 or ORs ≤ 0.67) revealed veterans who were ages 60 or older with alcohol use disorder or an adjustment disorder diagnosis were associated with greater incidence of any cancer; veterans with any suicidal ideation/behavior were at lower risk for cancer. Among HUH veterans, these effects were similar with older veterans and veterans with alcohol use disorder being at greater risk for cancer. Suicidal ideation/behavior was associated with lower risk of cancer.

Table 4.

Logistic regression of sociodemographic and psychiatric characteristics associated with any incidence of cancer among SH compared with HUH veterans.

SH veteransHUH veterans
VariableOR (95% CI)POR (95% CI)P
Age (ref 80+) 
 17–29 0.06 (0.05–0.07) <0.001 0.04 (0.02–0.07) <0.001 
 30–39 0.11 (0.10–0.13) <0.001 0.07 (0.05–0.10) <0.001 
 40–49 0.29 (0.27–0.31) <0.001 0.19 (0.14–0.25) <0.001 
 50–59 1.00 (0.96–1.05) .953 0.71 (0.56–0.91) 0.000 
 60–69 1.85 (1.79–1.92) <0.001 1.30 (1.02–1.65) 0.006 
 70–79 1.68 (1.62–1.75) <0.001 1.24 (0.96–1.62) 0.032 
Female 0.68 (0.64–0.72) <0.001 0.77 (0.65–0.91) <0.001 
Race/ethnicity (ref non-Hispanic white) 
 Non-Hispanic Black 1.33 (1.29–1.36) <0.001 1.23 (1.14–1.33) <0.001 
 Hispanic 0.89 (0.84–0.93) <0.001 0.82 (0.69–0.98) 0.004 
 Mixed race/other 0.81 (0.75–0.87) <0.001 0.95 (0.77–1.18) 0.569 
 Missing 0.75 (0.71–0.79) <0.001 0.75 (0.61–0.92) 0.000 
Marital status (ref married) 
 Single/never married 1.38 (1.33–1.44) <0.001 1.10 (0.98–1.23) 0.029 
 Divorced/separated 1.48 (1.45–1.52) <0.001 1.15 (1.04–1.26) 0.000 
 Widowed 1.34 (1.28–1.39) <0.001 1.22 (1.03–1.44) 0.003 
Percent service connected (ref none/0%) 
 10%–40% 0.87 (0.85–0.90) <0.001 0.86 (0.78–0.95) 0.000 
 50%–100% 1.04 (1.01–1.06) .000 0.91 (0.83–0.99) 0.006 
Combat exposure 1.02 (0.99–1.05) .070 1.05 (0.93–1.18) 0.290 
Military sexual trauma 0.82 (0.77–0.89) <0.001 0.91 (0.79–1.06) 0.108 
Diagnoses (year following index date) 
Alcohol use disorder 2.37 (2.27–2.46) <0.001 1.74 (1.60–1.88) <0.001 
Drug use disorder 1.17 (1.10–1.25) <0.001 1.08 (0.99–1.18) 0.026 
Schizophrenia spectrum disorder 1.00 (0.92–1.08) .879 1.00 (0.87–1.16) 0.941 
Other psychosis 1.34 (1.26–1.44) <0.001 1.07 (0.94–1.22) 0.185 
Depression 1.16 (1.11–1.21) <0.001 1.24 (1.12–1.38) <0.001 
Bipolar disorder 0.91 (0.85–0.99) .003 0.90 (0.80–1.02) 0.034 
Generalized anxiety disorder 0.76 (0.69–0.84) <0.001 0.86 (0.70–1.05) 0.053 
Other anxiety disorder 1.41 (1.35–1.46) <0.001 1.20 (1.09–1.32) <0.001 
Post-traumatic stress disorder 0.91 (0.87–0.95) <0.001 0.98 (0.89–1.08) 0.596 
Other adjustment disorder 1.66 (1.57–1.75) <0.001 1.35 (1.22–1.49) <0.001 
Other mental health disorder 1.24 (1.19–1.29) <0.001 1.18 (1.08–1.29) <0.001 
Suicidal ideation/behavior 0.65 (0.57–0.75) <0.001 0.58 (0.49–0.69) <0.001 
SH veteransHUH veterans
VariableOR (95% CI)POR (95% CI)P
Age (ref 80+) 
 17–29 0.06 (0.05–0.07) <0.001 0.04 (0.02–0.07) <0.001 
 30–39 0.11 (0.10–0.13) <0.001 0.07 (0.05–0.10) <0.001 
 40–49 0.29 (0.27–0.31) <0.001 0.19 (0.14–0.25) <0.001 
 50–59 1.00 (0.96–1.05) .953 0.71 (0.56–0.91) 0.000 
 60–69 1.85 (1.79–1.92) <0.001 1.30 (1.02–1.65) 0.006 
 70–79 1.68 (1.62–1.75) <0.001 1.24 (0.96–1.62) 0.032 
Female 0.68 (0.64–0.72) <0.001 0.77 (0.65–0.91) <0.001 
Race/ethnicity (ref non-Hispanic white) 
 Non-Hispanic Black 1.33 (1.29–1.36) <0.001 1.23 (1.14–1.33) <0.001 
 Hispanic 0.89 (0.84–0.93) <0.001 0.82 (0.69–0.98) 0.004 
 Mixed race/other 0.81 (0.75–0.87) <0.001 0.95 (0.77–1.18) 0.569 
 Missing 0.75 (0.71–0.79) <0.001 0.75 (0.61–0.92) 0.000 
Marital status (ref married) 
 Single/never married 1.38 (1.33–1.44) <0.001 1.10 (0.98–1.23) 0.029 
 Divorced/separated 1.48 (1.45–1.52) <0.001 1.15 (1.04–1.26) 0.000 
 Widowed 1.34 (1.28–1.39) <0.001 1.22 (1.03–1.44) 0.003 
Percent service connected (ref none/0%) 
 10%–40% 0.87 (0.85–0.90) <0.001 0.86 (0.78–0.95) 0.000 
 50%–100% 1.04 (1.01–1.06) .000 0.91 (0.83–0.99) 0.006 
Combat exposure 1.02 (0.99–1.05) .070 1.05 (0.93–1.18) 0.290 
Military sexual trauma 0.82 (0.77–0.89) <0.001 0.91 (0.79–1.06) 0.108 
Diagnoses (year following index date) 
Alcohol use disorder 2.37 (2.27–2.46) <0.001 1.74 (1.60–1.88) <0.001 
Drug use disorder 1.17 (1.10–1.25) <0.001 1.08 (0.99–1.18) 0.026 
Schizophrenia spectrum disorder 1.00 (0.92–1.08) .879 1.00 (0.87–1.16) 0.941 
Other psychosis 1.34 (1.26–1.44) <0.001 1.07 (0.94–1.22) 0.185 
Depression 1.16 (1.11–1.21) <0.001 1.24 (1.12–1.38) <0.001 
Bipolar disorder 0.91 (0.85–0.99) .003 0.90 (0.80–1.02) 0.034 
Generalized anxiety disorder 0.76 (0.69–0.84) <0.001 0.86 (0.70–1.05) 0.053 
Other anxiety disorder 1.41 (1.35–1.46) <0.001 1.20 (1.09–1.32) <0.001 
Post-traumatic stress disorder 0.91 (0.87–0.95) <0.001 0.98 (0.89–1.08) 0.596 
Other adjustment disorder 1.66 (1.57–1.75) <0.001 1.35 (1.22–1.49) <0.001 
Other mental health disorder 1.24 (1.19–1.29) <0.001 1.18 (1.08–1.29) <0.001 
Suicidal ideation/behavior 0.65 (0.57–0.75) <0.001 0.58 (0.49–0.69) <0.001 

Note: Bolded values are OR ≥1.50 or OR ≤ 0.67.

To determine whether these mental health conditions mostly preceded or followed cancer diagnoses, we conducted a supplementary analysis (Table 5). The results showed that most psychiatric conditions were documented before cancer diagnoses. While there were increases in psychiatric diagnoses among SH veterans after cancer diagnosis, particularly in major depression, adjustment disorder, and other mental health disorders (Δ2.2%–3.3%), there were not similar increases in these psychiatric diagnoses found among HUH veterans and even reductions in diagnoses of alcohol use and drug use disorders (Δ5.3%–6.6%) and suicidal ideation/behavior (Δ3.2%) after cancer diagnosis.

Table 5.

Rates of psychiatric conditions diagnosed before and after cancer diagnoses among veterans accessing VA health care.

Non-homelessHomeless
Pre cancer diagnosisPost cancer diagnosisPre cancer diagnosisPost cancer diagnosis
DiagnosisN%N%Δ%N%N%Δ%
Suicidal ideation/behavior 287 0.6% 301 0.6% 0.0% 272 7.1% 149 3.9% −3.2% 
Alcohol use disorder 2,316 4.9% 2,568 5.5% 0.5% 1,139 29.8% 938 24.5% −5.3% 
Drug use disorder 1,201 2.6% 1,297 2.8% 0.2% 1,023 26.8% 772 20.2% −6.6% 
Depression 9,162 19.6% 10,721 22.9% 3.3% 1,791 46.8% 1,760 46.0% −0.8% 
Bipolar disorder 708 1.5% 750 1.6% 0.1% 248 6.5% 234 6.1% −0.4% 
Generalized anxiety disorder 419 0.9% 424 0.9% 0.0% 78 2.0% 71 1.9% −0.2% 
Other anxiety disorder 1,944 4.2% 2,792 6.0% 1.8% 421 11.0% 415 10.9% −0.2% 
Schizophrenia spectrum disorder 714 1.5% 713 1.5% 0.0% 202 5.3% 191 5.0% −0.3% 
Other psychosis 719 1.5% 968 2.1% 0.5% 207 5.4% 184 4.8% −0.6% 
Post-traumatic stress disorder 4,380 9.4% 4,465 9.5% 0.2% 669 17.5% 596 15.6% −1.9% 
Adjustment disorder 1,077 2.3% 2,178 4.6% 2.4% 396 10.4% 433 11.3% 1.0% 
Other mental health disorder 5,110 10.9% 6,141 13.1% 2.2% 1,270 33.2% 1,195 31.3% −2.0% 
Non-homelessHomeless
Pre cancer diagnosisPost cancer diagnosisPre cancer diagnosisPost cancer diagnosis
DiagnosisN%N%Δ%N%N%Δ%
Suicidal ideation/behavior 287 0.6% 301 0.6% 0.0% 272 7.1% 149 3.9% −3.2% 
Alcohol use disorder 2,316 4.9% 2,568 5.5% 0.5% 1,139 29.8% 938 24.5% −5.3% 
Drug use disorder 1,201 2.6% 1,297 2.8% 0.2% 1,023 26.8% 772 20.2% −6.6% 
Depression 9,162 19.6% 10,721 22.9% 3.3% 1,791 46.8% 1,760 46.0% −0.8% 
Bipolar disorder 708 1.5% 750 1.6% 0.1% 248 6.5% 234 6.1% −0.4% 
Generalized anxiety disorder 419 0.9% 424 0.9% 0.0% 78 2.0% 71 1.9% −0.2% 
Other anxiety disorder 1,944 4.2% 2,792 6.0% 1.8% 421 11.0% 415 10.9% −0.2% 
Schizophrenia spectrum disorder 714 1.5% 713 1.5% 0.0% 202 5.3% 191 5.0% −0.3% 
Other psychosis 719 1.5% 968 2.1% 0.5% 207 5.4% 184 4.8% −0.6% 
Post-traumatic stress disorder 4,380 9.4% 4,465 9.5% 0.2% 669 17.5% 596 15.6% −1.9% 
Adjustment disorder 1,077 2.3% 2,178 4.6% 2.4% 396 10.4% 433 11.3% 1.0% 
Other mental health disorder 5,110 10.9% 6,141 13.1% 2.2% 1,270 33.2% 1,195 31.3% −2.0% 

Using administrative records from the largest integrated health care system for veterans, we found that the 1-year incidence of cancer was about 21.5% lower among HUH veterans compared with SH veterans. This finding held true even after adjusting for sociodemographic and psychiatric factors and contrasts with those of previous studies that have found greater risk of cancer in general homeless adult populations (2–4). It is possible that HUH veterans who have access to the VA's comprehensive health care system and a continuum of homeless services may not experience this particular health disparity as observed in other homeless populations. In addition, previous studies have also mainly focused on prevalence of cancer instead of cancer incidence as this study does. It is also possible that cancer was more likely to be underdiagnosed among HUH veterans, although we did not find major differences in stage of cancer diagnosed. It should also be noted that we used data from 2013 to 2014 given the time lag for cancer registry data and we used the most current dates of diagnoses that have been abstracted and verified by the VACCR. There have been new developments in cancer screening, such as VA's use of CT scans to screen for lung cancer (17) and the VA's National Tele-Oncology Service (18), which were not reflected in these data. So further study is needed to determine rates of undiagnosed cancer and effectiveness of new screening methods in the HUH veteran population.

When different cancer types were examined, the most common primary sites of cancer were similar between HUH and SH veterans, namely, cancer of the prostate, lung, and bronchus. However, beyond those primary sites, there were differences between HUH and SH veterans on other primary sites of cancer. Most notably, HUH veterans were more likely to have cancer of the liver. It is well documented that many HUH veterans have extensive histories of substance abuse and there is a high prevalence of various substance use disorders in this population (19–21). Misuse of substances can increase risk for liver cancer, and sharing of needles involved in substance abuse may also increase risk for hepatitis C and other diseases that may also increase risk for liver cancer. This is also consistent with our finding that alcohol use disorder was strongly associated with any cancer incidence in both SH and HUH veterans. We found that alcohol use disorder was commonly diagnosed before cancer diagnosis which would be consistent with a large body of literature documenting the negative health effects of frequent alcohol use (22) and its conferred risk for various types of cancer (22, 23). With high rates of alcohol use disorder found in HUH veterans (19, 20), this may be a particularly important risk factor to consider when treating HUH veterans.

SH veterans had higher incidence of cancer of the hematopoietic and reticuloendothelial systems, bronchus and lung, bladder, and melanoma of the skin than HUH veterans. It is not clear why this is and we are not able to determine whether this is higher incidence of detection of these cancers or these findings reflect true differences in incidence. It is possible that certain lifestyle or environmental factors (e.g., lower rates of obesity, greater sun exposure) of HUH veterans decrease risk for certain cancers. But clearly further study is needed to validate these findings and explore explanatory reasons for them.

Regression analyses using a comprehensive set of sociodemographic and psychiatric factors revealed that factors associated with cancer incidence was largely similar between HUH and SH veterans. Older age was the largest factor associated with any incidence of cancer which is not surprising. However, this may be worth noting because some studies suggest homeless populations experience “premature aging” as they have been found to die at earlier ages, are more likely to have chronic health conditions, and experience earlier onset of physical and cognitive decline than SH populations (24–27). This premature aging may not directly translate to cancer risk, but it may translate to greater difficulties in managing, seeking, and adhering to cancer treatment and care.

Interestingly, suicidal ideation and behaviors were negatively associated with cancer incidence among HUH and SH veterans. It is not entirely clear the reason for this, but we did examine the extent to which suicidal ideation/behaviors preceded or followed incident cancer. We found that documented suicidal ideation/behaviors and other mental health conditions largely preceded a cancer diagnosis among HUH and SH veterans. The prevalence of suicidal ideation we found among veterans with cancer was similar to the general adult population, although completed suicides have been found to be higher in cancer populations (28). Given the VA's decades long focus on suicide prevention (29), our findings about suicide risk and cancer may warrant further study. Interestingly, we found a reduction in suicidal ideation/behaviors after cancer diagnosis specifically among HUH veterans along with notable decreases in diagnoses of substance use disorders and small decreases in mental health disorders among HUH veterans. This finding is in contrast to SH veterans where small increases were observed in diagnoses of depression, adjustment disorder, and other anxiety disorders after cancer diagnosis, which is more consistent with previous studies that have reported cancer and cancer treatment directly or indirectly increasing mental health problems (30, 31). It is not entirely clear why decreases were observed in HUH veterans, but we speculate that it may be that a diagnosis of cancer may motivate some veterans to reduce their substance use and seek more mental health treatment along with their medical care. Because HUH veterans experience higher rates of mental health and substance use disorders than SH veterans in general, HUH veterans may be even more impacted by a cancer diagnosis than SH veterans. There is a body of literature that has documented the many lifestyle behavior changes adults with cancer adopt after a cancer diagnosis (32–34). Regardless of the timing of the onset of psychiatric disorder in relation to cancer, we found that mental health problems were common among veterans with cancer; for example, over one-fifth had a diagnosed depressive disorder. These findings underscore the importance of considering psychiatric and addiction disorders in identifying risk for cancer as well as treating the outcomes and sequalae of cancer.

There were several study limitations worth noting. This was an observational study using medical records and we cannot infer causality. Data were based on timely and accurate documentation of providers in the VA's medical record system. Some VA medical centers do not offer cancer treatment services and HUH veterans face various access issues (transportation) so differential access to care for HUH veterans may have affected the results. Our sample only included veterans who used VA health care and the results may not generalize to many HUH veterans who may not be in the VA system. These limitations were counterbalanced by the strengths of the study which included a large multi-year sample, multivariable analyses including various sociodemographic and psychiatric factors, and contribution to the sparse literature on cancer in HUH populations. Together, the findings of this study highlight the incidence and important clinical considerations that are needed to detect and treat cancer in HUH veterans. The lower rate of cancer in HUH veterans is complicated by the much higher rate of psychiatric disorders in this population before and after cancer diagnosis which is important in clinical practice.

L.L. Zullig reports other support from Novartis outside the submitted work. No disclosures were reported by the other authors.

J. Tsai: Conceptualization, supervision, writing–original draft, writing–review and editing. D. Szymkowiak: Data curation, formal analysis, writing–review and editing. L.L. Zullig: Validation, writing–review and editing.

There was no specific funding for this project and this project was supported by the Veterans Health Administration's Homeless Programs Office.

The publication costs of this article were defrayed in part by the payment of publication fees. Therefore, and solely to indicate this fact, this article is hereby marked “advertisement” in accordance with 18 USC section 1734.

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