Objective: Risk appraisal tools are increasingly being used in the clinical setting to estimate individuals' risks of developing and dying from diseases. The Harvard Cancer Risk Index is one such tool constructed to predict the risks of individuals, aged 40 and above, for developing the leading types of cancer in U.S. men and women relative to the general population. To date, the Risk Index has not been prospectively validated.
Study design and setting: Over a period of 10 years' follow-up in the Nurses' Health Study and the Health Professionals' Follow-up Study, age-standardized incidence ratios for cancer of the ovary, colon, and pancreas were calculated for the Risk Index's relative risk categories to assess goodness of fit for risk prediction at the aggregate level. Age-adjusted concordance statistics were determined as measures of discriminatory accuracy at the individual level.
Results: The Risk Index was well calibrated with observed relative risks across categories for ovarian and colon cancer in women and pancreatic cancer in men, while it performed moderately for colon cancer in men. Discriminatory accuracy was modest for ovarian cancer (age-adjusted concordance statistic = 0.59), and relatively good for pancreatic cancer (concordance statistic of 0.72), and colon cancer in men and women (concordance statistics of 0.71, 0.67 respectively).
Conclusion: The results of this prospective validation provide evidence for the validity of the Risk Index in predicting individuals' risks of cancers, and thereby offer support for future applications of this risk appraisal tool.