Clinical and histological features of second breast cancers following radiotherapy for childhood and young adult malignancy.

The purpose of this study was to determine the characteristics of early second breast cancer (SBC) among survivors of childhood and young adult malignancy treated with irradiation. We conducted a multicenter retrospective study of women who presented with breast cancer aged 50 years or younger in nine French centers. 121 patients and 141 SBC were analyzed (invasive = 130; non-invasive = 11). The mean age at first cancer diagnosis was 15 years and at initial SBC diagnosis was 38 years. Bilateral disease before the age of 51 years was diagnosed in 16% of the females. The majority of SBC were invasive carcinomas (92%). Among the invasive carcinomas, 39% had a histoprognostic score of III, 3.1% overexpressed HER2 and 29% were triple negative. The proportion of triple negative phenotype SBC was higher in patients older at first cancer diagnosis [RR = 1.2, 95% CI (1.1–1.3)]. 94% of triple negative SBCs developed in breast tissue which had received >20 Gy. We found a high proportion of aggressive SBC following thoracic radiotherapy in childhood or early adulthood. SBC screening is recommended by scientific societies for these child/young–adulthood cancer survivors in the same way as the one for high risk women because of constitutional mutations. Our results support these recommendations, not only because of a similar cumulative risk, but also because of the aggressive histological characteristics. [ABSTRACT FROM AUTHOR]