Assessing breast cancer risk models in Marin County, a population with high rates of delayed childbirth.
INTRODUCTION This study was designed to compare the Breast Cancer Risk Assessment Tool (BCRAT; Gail) International Breast Intervention Study (IBIS; Tyrer Cuzick) and BRCAPRO breast cancer risk assessment models using data from the Marin Women's Study, a cohort of women within Marin County, California, with high rates of breast cancer, nulliparity, and delayed childbirth. Existing models have not been well validated in these high risk populations. METHODS Discrimination was assessed using the area under the receiver operating characteristic curve (AUC) and calibration by estimating the ratio of expected to observed (E/O) cases. The models were assessed using data from 12,843 participants, of whom 203 had developed cancer during a 5 year period. All tests of statistical significance were 2 sided. RESULTS The IBIS model achieved an AUC of 0.65 (95% confidence interval [CI] 0.61 0.68) compared with 0.62 (95% CI, 0.59 0.66) for BCRAT and 0.60 (95% CI, 0.56 0.63) for BRCAPRO. The corresponding estimated E/O ratios for the models were 1.08 (95% CI, 0.95 1.25) 0.81 (95% CI, 0.71 0.93) and 0.59 (95% CI, 0.52 0.68) In women with age at first birth 30 years, the AUC for the IBIS, BCRAT, and BRCAPRO models was 0.69 (95% CI, 0.62 0.75) 0.63 (95% CI, 0.56 0.70) and 0.62 (95% CI, 0.56 0.68) and the E/O ratio was 1.15 (95% CI, 0.89 1.47) 0.81 (95% CI, 0.63 1.05) and 0.53 (95% CI, 0.41 0.68) respectively. CONCLUSIONS The IBIS model was well calibrated for the high risk Marin mammography population and demonstrated the best calibration of the 3 models in nulliparous women. The IBIS model also achieved the greatest overall discrimination and displayed superior discrimination for women with age at first birth 30 years.
Clinical breast cancer