Obesity, Disparities, and Treatment Advancements Shape US Cancer Trends

Results of the latest Annual Report to the Nation on the Status of Cancer show that although overall cancer death rates in the United States continue to decline—especially for lung cancer and melanoma—for prostate, colorectal, and female breast cancers, death rates continue to increase, or declines have slowed or even leveled off.

Several risk factors, including obesity, lack of physical activity, and increased drinking, appear to be fueling certain cancer trends, according to the report.

The findings underscore the need for increased prevention, early detection, and treatment efforts, in addition to broad, equitable interventions focused on under-resourced populations, authors wrote. Results were published in JNCI: The Journal of the National Cancer Institute.

Data reflect mortality trends reported from 2001 to 2018 in the United States and were compiled via a collaboration between The American Cancer Society, CDC, National Cancer Institute, and North American Association of Central Cancer Registries. Cancer incidence data represent cases reported between 2001 and 2017.

All trends reflect data collected prior to the COVID-19 pandemic.

“The declines in lung cancer and melanoma death rates are the result of progress across the entire cancer continuum - from reduced smoking rates to prevent cancer to discoveries such as targeted drug therapies and immune checkpoint inhibitors," said Karen E. Knudsen, MBA, PhD, the CEO of the American Cancer Society.

Despite numbers showing a decrease in cancer death rates for men and women from all racial and ethnic groups, overall cancer incidence grew among females, children, and adolescents and young adults. However, for children younger than 15 and those aged 15 to 29, death rates did decrease in contrast to increased incidence.

Analyses revealed:

• Overall cancer incidence rates (per 100,000 population) for all ages between 2013 and 2017 were 487.4 among males and 422.4 among females
• During this period, incidence rates remained stable among males but slightly increased in females (average annual percent change [AAPC] = 0.2%; 95% CI, 0.1% -0.2%)
• Overall cancer death rates (per 100,000 population) during 2014-2018 were 185.5 among males and 133.5 among females
• During this period, overall death rates decreased in both males (AAPC = −2.2%; 95% CI, −2.5% to −1.9%) and females (AAPC = −1.7%; 95% CI, −2.1% to −1.4%)
• Death rates decreased for 11 of the 19 most common cancers among males and for 14 of the 20 most common cancers among females, but increased for 5 cancers in each sex
• Between 2014 and 2018, the declines in death rates accelerated for lung cancer and melanoma, slowed down for colorectal and female breast cancers, and leveled off for prostate cancer
• 2-year relative survival for distant-stage skin melanoma was stable for those diagnosed between 2001 and 2009 but increased by 3.1% (95% CI, 2.8% - 3.5%) per year for those diagnosed from 2009 to 2014, with comparable trends among males and females

For both sexes, death rates increased for brain, some nervous system, and pancreas cancers, while rates also increased for oral cavity and pharynx cancers in males and liver and uterus cancers in females. Causes of increased deaths associated with cancers of the brain and nervous system are unclear and warrant additional research.

Cancer incidence rates continue to increase among females and adolescents and young adults, authors wrote. This fact, and the stabilized rates among males after earlier declines, largely reflects changes in cancer risk factors, notably increases in excess body weight, they explained.

Although trends reflect scientific advances yielding outcome differences at the population level, “I believe we could achieve even further improvements if we address obesity, which has the potential to overtake tobacco use to become the leading modifiable factor associated with cancer,” noted Norman E. "Ned" Sharpless, MD, the director of the National Cancer Institute at the NIH.

Total sitting time, in addition to the “staggering” rise in obesity among adults and youth, could impede efforts to decrease rates of associated cancers. “The increase of breast cancer incidence is largely driven by hormone-receptor positive cancer, which may in part reflect continuing reduction of parity rates, advanced age at first birth, the obesity epidemic (postmenopausal breast cancer), high levels of physical inactivity, and increase of alcohol consumption,” authors explained.

Poor outcomes for uterine, prostate, and kidney cancers are also all linked with obesity.

When it comes to race, breast cancer death rates are 40% higher among Black women than White women, regardless of similar incidence rates. Uterine cancer death rates are also twice as high among Black women, authors noted.

Overall cancer incidence rates were slightly lower among Black individuals compared with White populations while overall cancer death rates were higher among Black people. According to authors, this trend can be attributed to multiple factors including tumor biology, stage at diagnosis, receipt of timely and effective care, and systemic discrimination in cancer care delivery.

“It is encouraging to see a continued decline in death rates for many of the common cancers," said Karen Hacker, MD, MPH, the director of the CDC's National Center for Chronic Disease Prevention and Health Promotion.

However, “To dismantle existing health disparities and give everyone the opportunity to be as healthy as possible, we must continue to find innovative ways to reach people across the cancer care continuum--from screening and early detection to treatment and support for survivors,” she said.

Social determinants of health, such as exposure to cancer risk factors and limited access to healthy food, safe places for physical activity, and evidence-based preventive services exacerbate incidence and mortality trends.

"When evaluating health disparities, it is critical to acknowledge the social factors that influence the health of the communities and access to health care," said Betsy A. Kohler, MPH, the executive director of the North American Association of Central Cancer Registries.

"Social and economic indicators, particularly based on small area assessments, are increasingly important to understanding the burden of cancer."