Impact of inclusion of subsequent primary cancers on estimates of risks of developing cancer

Lifestyle, genes, and cancer

It is estimated that almost 1.5 million people in the USA are diagnosed with cancer every year. However, due to the substantial effect of modifiable lifestyle factors on the most prevalent cancers, it has been estimated that 50% of cancer is preventable. Physical activity, weight loss, and a reduction in alcohol use can strongly be recommended for the reduction of breast cancer risk. Similarly, weight loss, physical activity, and cessation of tobacco use are important behavior changes to reduce colorectal cancer risk, along with the potential benefit for the reduction of red meat consumption and the increase in folic acid intake. Smoking cessation is still the most important prevention intervention for reducing lung cancer risk, but recent evidence indicates that increasing physical activity may also be an important prevention intervention for this disease. The potential benefit of lifestyle change to reduce prostate cancer risk is growing, with recent evidence indicating the importance of a diet rich in tomato-based foods and weight loss. Also, in the cancers for which there are established lifestyle risk factors, such as physical inactivity for breast cancer and obesity for colorectal cancer, there is emerging information on the role that genetics plays in interacting with these factors, as well as the interaction of combinations of lifestyle factors. Integration of genetic information into lifestyle factors can help to clarify the causal relationships between lifestyle and genetic factors and assist in better identifying cancer risk, ultimately leading to better-informed choices about effective methods to enhance health and prevent cancer.

Risk-adjusted cancer-incidence rates (United States)

A risk-adjusted method is proposed for estimating cancer incidence rates from data collected by the Surveillance, Epidemiology, and End Results (SEER) program of the US National Cancer Institute. Unlike the conventional incidence-rate estimates reported by SEER, this method considers only the first primary cancer, and adjusts for population-based cancer prevalence, as well as for surgical procedures which remove an individual from risk of developing a given cancer. Thus, risk-adjusted incidence-rates more accurately reflect the average cancer risk for individuals in the cancer-free, at-risk population. The results of the analysis indicate that, in general, incidence-rate estimates are fairly similar between the conventional and risk-adjusted methods. However, this is not the case for certain cancer sites which may have: (i) a high number of subsequent primary cancers (e.g., melanomas-skin); (ii) a high cancer prevalence proportion (e.g., prostate cancer); (iii) a high number of subsequent primary cancers and prevalence proportion (e.g., female breast); or (iv) a high prevalence of removal of the organ in question (e.g., cervical and uterine cancers). For example, by applying the risk-adjusted incidence method for in situ and invasive cervical cancer, we found that in the period 1990-92 the age-adjusted incidence-rate estimate increased from 57.8 to 66.3 (15 percent) per 100,000 person-years; the greatest increase in the incidence-rate estimate occurred for women aged 65 to 69 years, from 40.1 to 63.2 (58 percent) per 100,000 person-years; and the lifetime risk of developing cervical cancer increased from 4.6 (1 in 22) to 5.5 (1 in 18) percent.