Synchronous and metachronous bilateral breast cancer: Are the risks greater in women with a history of radiation for Hodgkin lymphoma?

Abstract

607 Background: Women with a history of radiation therapy (RT) for Hodgkin lymphoma (HL) have an elevated risk of breast cancer (BC). The characteristics, treatment and outcomes of these cancers, compared with sporadic breast cancers, are not well described. In particular, rates of synchronous and metachronous bilateral BC may be greater in patients with a history of RT for HL. Methods: Women diagnosed with BC between 1980 and 2006 following RT for HL were identified retrospectively from 8 institutions in North America. Each patient in this cohort was matched with 3 BC patients with no history of HL, from the same institution, by age at BC diagnosis, year of BC diagnosis and race. Information on patient and tumor characteristics, disease recurrence and new contralateral tumors was obtained from medical records. Analysis of metachronous contralateral breast cancer (CBC) was limited to women with a breast at risk, and adjusted hazard ratios (HRs) for CBC were estimated using Cox proportional hazards regression. Results: 253 BC patients with a history of RT for HL were matched with 741 patients with sporadic BC. The median interval between HL and first BC diagnosis was 19 years. Median age at BC diagnosis was 44 years and median follow-up was 5 years from BC diagnosis. Synchronous bilateral BC was diagnosed in 6% of the HL survivors and 2% of the matched patients with sporadic BC. Among women with unilateral disease, 21% of HL survivors and 3% of sporadic BC patients had a bilateral mastectomy. Overall 64 women with a breast at risk developed metachronous CBC. BC patients with a history of RT for HL had a greater rate of metachronous CBC (adjusted hazard ratio 3.3, 95% CI 2.1–5.8), controlling for patient, tumor and treatment characteristics. In addition, those who received chemotherapy for BC were less likely to develop CBC (adjusted HR 0.51, 95% CI 0.31–0.85), and those with a family history of BC in a 1st degree relative were more likely to develop CBC (adjusted HR 1.8, 95% CI 1.1–3.0). Conclusions: Women who develop BC after RT for HL have more than 3 times the risk of CBC than similar women with sporadic BC. Our findings support close follow-up for CBC in BC patients with a history of RT for HL and may inform decisions about prophylactic mastectomy in this population. No significant financial relationships to disclose.