Clinicopathologic features of breast cancers diagnosed in women treated with prior radiation therapy for Hodgkin lymphoma: Results from a population-based cohort

Background Childhood and young adult survivors of Hodgkin lymphoma (HL) are at elevated risk of developing breast cancer, yet little data exist on the tumor characteristics that develop in this high-risk patient population. Methods The National Cancer Institute's Surveillance, Epidemiology, and End Results database was used to identify breast cancers diagnosed between 1990 and 2016 in women who had received prior radiation therapy for HL at age 30 years or younger. Clinicopathologic features of subsequent breast cancers (breast cancer after radiation therapy for HL [BC-HL]) were examined and compared with breast cancers diagnosed in women who had no prior malignancy (breast cancer with no prior malignancy [BC-NPM]). Results In total, 321 breast cancers were identified in 257 women who had a history of radiation therapy for HL. The median age at HL diagnosis was 22 years (interquartile range, 18-26 years), and nearly all patients in the BC-HL group (97.9%) were diagnosed >= 8 years after radiation therapy. Overall, 56 patients in the BC-HL group (21.8%) developed bilateral breast cancer. Compared with women who had BC-NPM, those who had BC-HL were younger (43 vs 60 years; P < .001) and were less likely to present with ductal carcinoma in situ (8.4% vs 14.9%; P = .001). On multivariable analysis that included adjustment for age, invasive BC-HL was associated with smaller (<= 2 cm) tumor size (odds ratio, 1.64; 95% CI, 1.25-2.15) and upper outer quadrant tumors (odds ratio, 1.37; 95% CI, 1.04-1.81) compared with BC-NPM. In a subset analysis of 102 women who had HER2/neu status available, the distribution of biologic subtype was not significantly different between BC-HL and BC-NPM (P = .16). Conclusions Breast cancers in women who previously received radiation therapy for HL are characterized by earlier onset disease, although most remain estrogen receptor-positive and have early stage disease at presentation. Lay Summary Women who have had radiation therapy for Hodgkin lymphoma at a young age are at increased risk of developing early onset breast cancer; however, most of these breast cancers are sensitive to hormones (estrogen receptor-positive) and are diagnosed at early stages. Because these breast tumors are estrogen receptor-positive, medications that prevent breast cancer by blocking the effect of or lowering hormone levels (also termed endocrine prevention) may be useful in this group of high-risk women.