The National Cancer Institute's Colorectal Cancer Risk Assessment Tool (NCI-CCRAT), an absolute risk prediction model, was developed using data from US White men and women. The model's performance has not been assessed for Black Americans, the US racial/ethnic group with the highest colorectal cancer (CRC) incidence. We externally validated the NCI-CCRAT using data from 53,324 Black Women's Health Study (BWHS) participants aged 40-84 years. We predicted 5-year absolute risks using data from 2001-2015 in three 5-year prediction periods: 2001-2005, 2006-2010, and 2011-2015. To assess model performance, we computed calibration (expected over observed CRC cases, E/O) and discriminatory accuracy (area under the receiver operating curve, AUC). During follow-up, 433 BWHS participants developed CRC. Based on the NCI-CCRAT, 579 CRC cases were expected (E/O=1.34,95% confidence interval CI:1.22-1.47). The NCI-CCRAT was well-calibrated in the first 5-year prediction period (2001-2005 E/O=1.10, 95%CI:0.94-1.29), but statistically significantly overestimated risk in later periods. We estimated discriminatory accuracy only for the 2001-2005 prediction period (151 CRC cases) and obtained an age-adjusted AUC=0.62 (95%CI:0.57-0.66). Associations of vigorous physical activity, aspirin/NSAID use, vegetable intake, and body mass index with CRC risk were weaker in the BWHS than in the studies used to develop the NCI-CCRAT. The NCI-CCRAT significantly overestimated the number of CRC cases in BWHS participants, possibly due to population-specific differences in associations of key CRC risk factors. This suggests that future research needs to determine important predictors of CRC risk in Black Americans and to develop a CRC prediction model for Black women.
Petrick et al. (Tue,) studied this question.