Cancer among Immigrants: Diverse Histories, Diverse Disparities, Diverse Opportunities to Promote Equity

“Migration is an expression of the human aspiration for dignity, safety, and a better future. It is part of the social fabric, part of our very make-up as a human family.” These words were spoken by the then United Nations Secretary General Ban Ki-moon almost a decade ago in his 2013 address to the 68^th Session of the General Assembly (1). Ban Ki-moon's words allude to not only the ethical imperative to provide “dignity, safety, and a better future” for peoples who are often amongst the most vulnerable in society; his words highlight the timeless and global ubiquity of immigration and human migration, the ancient and dynamic flow of humanity.

Immigrants–people who are broadly defined as individuals who live in a country different from their country of birth–constitute approximately 250 million people, representing over 3% of the global population (2). The United States is home to approximately 50 million immigrants, approximately 14% of the country's population (2). Immigrants represent 22% of the Canadian population, 28% of the Australian population, and over 70% of the populations in Persian Gulf nations such as Qatar, Kuwait, and the United Arab Emirates (2). Inherent to the needs of migrants everywhere is access to systems that uphold and promote their health. Therefore, it is critical in the context of cancer health to improve our understanding of the epidemiology of cancer amongst migrants so as to inform policy, screening, and management.

Early studies support the “healthy migrant effect,” that is, an idea that suggests that migrants have better health overall not just compared with people from their home country but also compared with people from their adopted country (3). However, migrants are diverse in their reasons for immigration, ranging from those who are forced to flee their home country for survival, to those seeking a better life. Disparities and barriers in access to health permeate the experiences of migrants the world over, ranging from lower rates of insurance to linguistic and cultural barriers to access to deleterious health policies that seem to promote inequities experienced by those most vulnerable (3–5). For example, studies from Sweden suggest that although migrants from other Western countries may have better health on average than native Swedes, similar conclusions were not supported amongst non-Western immigrants (3). Studies from the United States and Canada suggest that some migrant groups experience lower rates of cancer screening (6, 7); cancer disparities across the disease spectrum particularly affect people who are undocumented or those who are refugees (8), who often experience extreme poverty (9). These disparities in cancer incidence, care, and outcomes are as diverse as the people who experience them.

In this issue of Cancer Epidemiology, Biomarkers & Prevention, Yu and colleagues evaluate patterns in the incidence of infection-associated cancers amongst migrants in Australia (10). The authors chose to study infection-associated cancers because of data that suggests that immigrants from lower-resourced countries may be at greater risk of infection-associated cancers (11). In addition, infections are intervenable causes of cancer (12). As a nation with a long and diverse history of immigration–ranging from pre-World War II migrants from the United Kingdom and Ireland to the postwar diaspora first from continental Europe and then also from Eastern and Southeastern Asia–Australia's heterogeneous and significant migrant populations merit dedicated study that may inform efforts to mitigate cancer disparities and improve access to cancer care.

In their examination of the Australian national incidence of cancers of the stomach, liver, and cervix, the authors demonstrate significant variations in incidence by country of birth. Rates of stomach cancer were highest amongst migrants from Italy, Greece, and China; rates of liver cancer were highest amongst migrants from Vietnam, China, and Italy. Therefore, the incidences of stomach and liver cancers were higher amongst Australian migrants from countries with higher incidences of these cancers. In addition, rates of cervical cancer were greater amongst Australian migrants from the Philippines, New Zealand, and Polynesia, and were lower for women from South Asian and North African countries. In addition to rigorous statistical analyses, the quality of the study is supported by legislation that requires that all cancers diagnosed in Australia are reported to the jurisdictional cancer registry. Furthermore, these cancer registries routinely collect country or region of birth.

The authors acknowledge limitations in their work: the lack of data regarding infection history, detailed data regarding patients’ educational attainment, health literacy, and socioeconomic status, as well as data regarding other factors that influence recorded cancer incidence such as screening and disease-specific risk factors. Future studies should include analyses that incorporate these factors to further elucidate intervenable risk factors. In addition, further work should use a qualitative lens to explore issues of access, and other structural and social determinants, faced by various immigrant groups.

The work of Yu and colleagues is an important addition to our understanding of the cancer health of migrants in Australia. Their work demonstrates that the incidence of infection-related cancers is heterogeneous amongst immigrant populations, and underscores the value of studies that disaggregate groups by race/ethnicity in ways that reflect the diversity amongst these groups. Studies of immigrants and descendants of immigrants in the United States and elsewhere have also demonstrated wide-ranging heterogeneity amongst these groups (13–15). Work that seeks to elucidate cancer priorities as well as challenges that are specific to race/ethnic and migrant subpopulations is necessary to inform strategies that are aligned with each group's needs.

For example, the finding from Yu and colleagues that suggests that the incidences of infection-associated cancers amongst immigrants may parallel those of these individuals' countries of origin could inform screening practices in Australia. The authors find that gastric cancer is greater amongst immigrants from East Asia and the Mediterranean. These findings can inform efforts to design endoscopic screening for these populations. For example, in the United States, ongoing efforts exist to improve access to gastric cancer screening for Korean Americans, whose incidence of gastric cancer likely reflect the elevated incidence in Korea (16, 17). Recent work has shown that gastric cancer screening may be cost-effective for Asian-American populations (16); these findings should be taken into consideration as policymakers work to define screening guidelines for these populations. Parallel questions are being asked in the United States and other countries with regard to the role of low-dose CT screening for lung cancer given evidence suggesting increased incidence amongst non-smoking women of Asian descent (18, 19). The work of Yu and colleagues may similarly inform cancer screening practices in Australia.

Another example is the role of human papillomavirus (HPV) vaccination and cervical cancer screening amongst immigrant populations. Yu and colleagues find that rates of cervical cancer vary greatly amongst immigrant groups. The authors suggest that more work is needed to elucidate the causes of these differences, but differences in rates of HPV vaccination and cervical cancer screening are likely key drivers of broad differences in incidence. Although HPV vaccination and cervical cancer screening are free for women of eligible age in Australia (20), efforts are needed to educate groups–particularly those who are at greater risk–regarding the benefits of these preventive interventions. Data are limited with regard to rates of HPV vaccination and cervical cancer screening disaggregated by race/ethnicity and country of birth; such work in conjunction with the findings of Yu and colleagues may improve our understanding of how to optimize vaccination and screening strategies for these subpopulations. Work from Canada has identified multi-dimensional causes of lower rates of cervical cancer screening amongst some immigrant groups, including linguistic, cultural, economic, and health literacy factors (21). Building upon the work of Yu and colleagues, work in Australia and other countries may inform culturally tailored interventions (22). In addition to guiding screening and prevention strategies, a greater understanding of cancer incidence may inform a provider's differential diagnosis for patients presenting with symptoms that may be concerning for malignancy.

This work also highlights wider issues that affect immigrant populations the world over. For example, greater rates of liver cancer amongst immigrants may represent not just higher rates of infection in the countries from where certain immigrant groups come (23); these high and often sustained liver cancer incidences may also represent poor access to antiviral therapy, linguistic barriers to screening and treatment, and socioeconomic barriers to care (5, 23). Greater rates of gastric cancer amongst certain subpopulations may suggest the lack of culturally tailored screening patterns or poor access to potentially costly endoscopy-based screening (24). Higher rates of cervical cancer among certain groups may represent disparities in sociocultural barriers, health literacy, or other stigma that merit further intervention (25). The work of Yu and colleagues is an important next step in informing the ways in which we care for immigrants, and is translatable to other countries; next steps can take this work further to identify how best to optimize interventions for people who are often the most vulnerable.

The words of Ban Ki-moon ring true: migration, and more importantly, the migrant people whose narratives constitute migration, are part and parcel of “our very make-up as a human family.” They are people who choose to or are forced to leave one home to create another home in adopted lands and amongst adopted people. They are often amongst the most vulnerable in society, and face diverse challenges in ensuring their own health. Therefore, the onus falls on the research and medical communities to work to elucidate their diverse stories, understand their diverse disparities, and act upon diverse opportunities to promote equity.

E.C. Dee reports grants from NCI during the conduct of the study. S.L. Gomez reports grants from NIH during the conduct of the study.

E.C. Dee is funded in part through the Cancer Center Support Grant from the NCI (grant no. P30 CA008748).