Breast cancer risk assessment across the risk continuum: genetic and non-genetic risk factors contributing to differential model performance
A partir de données portant sur une cohorte prospective de 1 857 femmes (durée moyenne de suivi : 8,1 ans, 83 cas de cancer du sein), cette étude évalue les performances de deux modèles d'estimation du risque de cancer du sein à 10 ans
INTRODUCTION:Clinicians use different breast cancer risk models for patients considered at average and above-average risk, based largely on their family histories and genetic factors. We used longitudinal cohort data from women whose breast cancer risks span the full spectrum to determine the genertic and non-genetic covariates that differentiate the performance of two commonly used models that include non-genetic factors -- BCRAT, or also called GAIL model generally used for patients with average risk and IBIS (also called Tyrer Cuzick model) generally used for patients with above-average risk.
METHODS:We evaluated the performance of the BCRAT and IBIS models as currently applied in clinical settings for ten-year absolute risk of breast cancer, using prospective data from 1,857 women over a mean follow-up length of 8.1 years, of whom 83 developed cancer. This cohort spans the continuum of breast cancer risk, with some subjects at lower than average population risk. Therefore, the wide-variation in individual risk makes it an interesting population to examine model performance across subgroups of women. For model calibration, we divided the cohort into quartiles of model-assigned risk and compared differences between assigned and observed risks using the Hosmer-Lemeshow (HL) chi-squared statistic. For model discrimination, we computed the area under the receiver operator curve (AUC) and the case risk percentiles (CRPs).
RESULTS:The ten-year risks assigned by BCRAT and IBIS differed (range of difference 0.001 to 79.5). The mean BCRAT- and IBIS-assigned risks of 3.18% and 5.59%, respectively, were lower than the cohort's 10-year cumulative probability of developing breast cancer (6.25%; 95% confidence interval (CI) = 5.0-7.8%). Agreement between assigned and observed risks was better for IBIS (HL X42 =7.2, P-value 0.13) than BCRAT (HL X42 = 22.0, P-value < 0.001). The IBIS model also showed better discrimination (AUC = 69.5%, CI = 63.8% - 75.2%) than did the BCRAT model (AUC = 63.2%, CI = 57.6% - 68.9%). In almost all covariate-specific subgroups, BCRAT mean risks were significantly lower than the observed risks, while IBIS risks showed generally good agreement with observed risks, even in the subgroups of women considered at average risk (e.g., no family history of breast cancer, BRCA1/2 mutation negative).
CONCLUSIONS:Models developed using extended family history and genetic data, such as the IBIS model, also perform well in women considered at average risk (e.g. no family history of breast cancer, BRCA1/2 mutation negative). Extending such models to include additional nongenetic information may improve performance in women across the breast cancer risk continuum.
Breast Cancer Research , article en libre accès, 2011