Gender differences in colorectal cancer: implications for age at initiation of screening

Family history and age at initiation of colorectal cancer screening

OBJECTIVES

To review and combine the best available epidemiological evidence, by sex and age, that may help decision and policy makers form recommendations as to how much earlier colorectal cancer (CRC) screening should be initiated among people with a family history of CRC than among average-risk people.

PATIENTS AND METHODS

Combining population-based cancer registry and health interview survey data from the United States and results of a recent meta-analysis of epidemiological studies, we estimated cumulative incidence of CRC within subsequent 10 yr (CI(10)) at various ages among men and women with and without a family history of CRC. We estimated both the CI(10) levels reached in average-risk 45-, 50-, 55-, and 60-yr-old men and women and the age at which the same CI(10) levels are reached in men and women with a history of CRC in a first-degree relative.

RESULTS

Despite major differences in CRC risk by sex, and despite the strong age gradient in relative risk associated with a positive family history, "risk advancement periods" for those with a family history were consistently found to be between 9 and 11 yr for both sexes and at all four ages assessed.

CONCLUSION

Advancement of first CRC screening by 10 yr among both men and women with a family history of CRC compared to the average-risk population (e.g., from 50 to 40 yr of age) appears to be a reasonable, evidence-based recommendation.

Should colorectal cancer screening start at the same age in European countries? Contributions from descriptive epidemiology

We assessed incidence and mortality of colorectal cancer (CRC) at various ages among women and men in 38 European countries. The ages at which defined levels of incidence and mortality were reached varied between 9 and 17 years between countries. This variation requires consideration in the definition of screening guidelines.

Evaluation of screening strategies for pre-malignant lesions using a biomathematical approach

We derive mathematical expressions for the size distribution of screen-detectable pre-malignant lesions, both conditional and unconditional on no prior detection of cancer in the tissue of interest, based on a general multistage clonal expansion model of carcinogenesis. We apply these expressions to simulate the natural history of colorectal cancer and to evaluate the effect of a screen for adenomatous polyps and concomitant intervention on cancer risk. Our approach allows the efficient simulation of multiple screens and interventions and determination of the optimal timing of the screens. We further demonstrate the utility of our approach by computing the benefits of up to two colonoscopies on the lifetime risk of colorectal cancer.