Realistic (and Still Idealistic) about Cancer Prevention

After almost 30 years as an ASPO member, I still believe in prevention, but I am more realistic about what that means.

Cancer trends over the past decade irrefutably demonstrate that behaviors and environmental factors are pivotal factors in cancer occurrence. A striking illustration, stomach cancer, once the most common cancer in the United States, is now the least common, and lung cancer, rare in 1930s, is now the leading cause of cancer-related death among men and women. What Sirs Doll and Peto so convincingly concluded in their seminal 1981 Journal of the National Cancer Institute monograph, “The Causes of Cancer: Quantitative Estimates of Avoidable Risks of Cancer in the United States Today,” is captured in dramatic, parabolic trend lines: the majority of cancer-related deaths might be eliminated by avoiding exposures now known to be important risk factors (e.g., consuming contaminated food rife with bacteria and smoking).

The sentiment expressed by Doll and Peto, “Cancer is preventable,” echoed many previous initiatives to eliminate cancer, beginning in 1937 when Roosevelt signed the National Cancer Institute (NCI) into effect and followed 35 years later by Nixon's signing the National Cancer Act in 1971. It would continue to reverberate through 1990s and beyond as the National Cancer Institute, American Cancer Society (ACS), and the White House each issued their own challenge goals to eliminate cancer-related deaths in the United States. Among them was the ambitious 1986 NCI initiative to reduce cancer mortality in the United States by 50% by 2000 (it was determined later that the reduction was, in fact, about 4%; ref. 1). A decade later, however, when the Board of Directors of the ACS issued a new initiative to reduce cancer mortality by 50% by the year 2015, the results were much more promising; for some cancers, such as lung, colorectal, prostate, and breast cancer, the target was actually met, by and large driven by a focus on the reduction in known risk factors, as well as by accessible improvements in early detection and treatment (1).

Aligned with these goals for reducing cancer incidence and mortality in the population, my own early career in cancer epidemiology focused on understanding modifiable risk factors, such as alcohol intake, hormone replacement therapy, and reproductive behaviors: ways in which altering one's lifestyle could reduce risk. That is, I quite naively believed cancer's occurrence was in the hands of the individual. Over the past few decades, many of these lifestyle risk factors have been extensively studied, and subsequently established in the scientific literature, clinical practice guidelines, and promulgated in the popular press. Moving forward, how can we look at known risk factors more granularly, and with an eye toward implementation, to further the field of cancer prevention?

While prevalence of some major risk factors for cancer has declined in past decades, others are on the steep rise. Rates of obesity are increasing across the country, contributing significantly to rising rates of hypertension, type II diabetes, heart disease, stroke, and cancer. The issue is further complicated by the fact that the burden of obesity and obesity-related conditions is faced disproportionately by racial and ethnic minorities, widening already existing health disparities. According to 2015 National Health Interview Survey data, American Indians and Alaska Natives had the highest-age adjusted rates of obesity (43.7%), followed by African Americans (39.5%), Latinos (38.9%), and non-Hispanic whites (32.9%). In addition to its serious health consequences, the estimated annual economic costs of obesity-related illness are a staggering $190.2 billion or nearly 21% of annual medical spending in the United States (2).

Despite the generally accepted role of obesity on the risk of many cancers, further study is needed to elucidate and possibly motivate interventions to improve the prognostic implications of postdiagnostic physical activity and weight loss. Furthermore, consideration is also needed for the effects of built environment, aspects such as neighborhood walkability and geographic proximity to grocery outlets with affordable, healthy food both in the context of incidence and longevity. Such a complex, multifactorial issue will likely require complex, multifactorial, and multilevel solutions.

By all accounts, the achievements made by the nationwide and local initiatives to eliminate smoking as the number one preventable cause of death should be considered a great public health success. However, in spite of these Herculean efforts and the well-established, widely acknowledged risks of smoking, tobacco control implementation remains a challenge.

In 1998, the state Attorneys General led by Washington Attorney General, Christine Gregoire, then Governor, now Chair of the Fred Hutchinson Board of Trustees, achieved a landmark decision against Big Tobacco. Each U.S. state promised to use a significant portion of their settlement funds—estimated at $206 billion—over the first 25 years to attack the enormous public health problems caused by smoking. Despite receiving huge funding allocations (in 2017 fiscal year, the states will collect $27 billion from the settlement and smoking-related taxes), states are spending less than 1.8% on programs to keep kids from smoking or help adults quit (3)—clearly not the intent of this court ruling. As of 2017, only three states are spending 50% or more of the Centers for Disease Control and Prevention (CDC) recommendation on tobacco prevention programs (Alaska, Oklahoma, North Dakota), while the majority of states, including Washington, spend less than 10% of the CDC recommendation on tobacco-related efforts (3).

Across the entire spectrum of diseases and health conditions, disparities persist with regards to prevention, screening, and treatment. With regards to cancer, racial and ethnic minorities have historically higher rates of incidence and more advanced disease at diagnosis (and poorer prognosis) than their white counterparts. Although these disparities have been attenuated in the past several decades, and a recent study reported that the proportion of late-stage cases became statistically similar in whites and blacks in 2010, disparities in cancer survival still persist (4). Health systems performance must be improved, and monitored, so that advances may be made available to all. Perhaps some of the answers lie in harnessing technological innovations, still in development, enabling new opportunities for more equitable intervention and success.

As Byers and colleagues stated, “As we embark on new national cancer goals, this recent past experience should teach us that curing the cancer problem will require 2 sets of actions: making new discoveries in cancer therapeutics and more completely applying those discoveries in cancer prevention we have already made” (5).

We need to be more scientifically informed and think creatively to explore yet understudied exposures such as environmental contaminants, stress, social interactions and networks, sleep, the microbiome, and climate change. To advance the field of cancer control forward, we need to harness new technology, including social media, mobile health, data science, and geospatial techniques.

• Dissemination and implementation: help people modify risky behaviors. Ask government, industry, academia, and the general public to maximally use the information we already have to reduce risk and improve outcomes.

• Health systems improvements: ensure access to interventions from risk reduction to early detection to treatment. Make sure cost is not a barrier to these improvements.

• Technological innovations: consider new opportunities for measuring exposures and intervening. This may seem too unchartered, but here in Seattle, you can see that Amazon, Microsoft, Starbucks, and Costco can teach us to successfully take risks in our own preventive oncology arena.

• Don’t give up on finding new risk factors, and don’t give up on methods to preventing our exposure to them.

No potential conflicts of interest were disclosed.

I would like to thank Ruth Etzioni and Kelsey Chun for their counsel in preparing these comments, and Heidi Sahel for keeping us all on our mission.