Novel indications forBRCA1 screening using individual clinical and morphological features

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Abstract
Since there is a lack of common family profile among BRCA1‐gene carriers, and since the risk of being a mutation carrier is not limited to women with a family history of breast or ovarian cancer, multivariate statistical analysis using the logistic‐regression model was carried out, to discriminate between sporadic cases and BRCA1‐breast cancers (BRCA1‐BCs), especially when information about the family history of breast/ovarian cancer and ethnicity are irrelevant or unavailable, in order to offer specific medical treatment to this population. We examined 32 BRCA1‐BCs selected at cancer genetic clinics and 200 consecutive controls without family history of breast cancer for age at onset and current morphological parameters. Following the multivariate analysis, 3 parameters only, namely, early age at cancer onset [odds ratio (OR) for each year = 1.16; p < 0.0001], estrogen‐receptor negativity (OR = 5.7; p = 0.01) and poor differentiation (OR = 5; p = 0.03) were found significant factors for predicting BRCA1‐carrier status. The expected impact in BRCA1 screening of our model was estimated using data on 5 700 breast‐cancer cases from a hospital‐based registry. Only 50 and 15% of tumours with early age at onset below 35 years present one or the other 2 discriminant parameters respectively. Consequently, whereas the probability of finding a BRCA1 mutation is rated low (6.2%) when the sole criterion of early onset up to the age of 35 years is used, based on our model, in the sub‐group of women with a tumor that is both estrogen‐receptor‐negative and poorly differentiated the mutation‐detection rate is predicted to be above the 10% chance level recommended by the ASCO guidelines. This sub‐group of women, representing about 1% of all breast‐cancer cases in Western countries, consequently deserves to be tested. Int. J. Cancer (Pred. Oncol.) 84:263–267, 1999.