Assessing breast cancer risk models in Marin County, a population with high rates of delayed childbirth.
BACKGROUND
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.
Marin Women's Study, Marin County Health and Human Services, San Rafael, CA. Electronic address: mpowell@marincounty.org.
Mark
M
Powell
Marin Women's Study, Marin County Health and Human Services, San Rafael, CA.
Farid
F
Jamshidian
Marin Women's Study, Marin County Health and Human Services, San Rafael, CA.
Kate
K
Cheyne
Marin Women's Study, Marin County Health and Human Services, San Rafael, CA.
Joanne
J
Nititham
Marin Women's Study, Marin County Health and Human Services, San Rafael, CA.
Lee Ann
LA
Prebil
Marin Women's Study, Marin County Health and Human Services, San Rafael, CA.
Rochelle
R
Ereman
D000328:Adult; D000368:Aged; D019540:Area Under Curve; D001943:Breast Neoplasms / Q000453:epidemiology*; D002140:California / Q000453:epidemiology; D016001:Confidence Intervals; D005260:Female; D006801:Humans; D008875:Middle Aged; D012372:ROC Curve; D043762:Reproductive Behavior; D018570:Risk Assessment; D012307:Risk Factors
Breast cancer risk prediction; Calibration; Discrimination; Nulliparity; Risk factors