Gail model risk factors: impact of adding an extended family history for breast cancer.

An approach commonly used in estimating breast cancer risk is the Gail model. The objective of this study was to evaluate the feasibility and impact of adding extended family history as a new breast cancer risk factor into the Gail model. The data of the present study include cases with breast cancer and hospitalized controls recruited in the National Cancer Institute of Naples (southern Italy) between 1997 and 2000. We compared the first-degree relative (FDR) risk factor (standard Gail model) with the second-degree relative (SDR) information; and the FDR risk factor (standard Gail model) with the combination of FDR and SDR. We computed the c-statistic by comparing the risks found in our population to those in Gail-US population. The concordance for the model with FDR was 0.55 (95% CI 0.53-0.58), the model with SDR shows a modest but significant discriminatory accuracy (0.56, 95% CI 0.53-0.59), and the combination of FDR+SDR gave the concordance statistic of 0.57 (95% CI 0.54-0.60), indicating a good comparison between the two models. The results of our study show that extended family history information could be useful to improve the discriminatory power of the Gail model risk factors.