In an analysis from the Blood or Marrow Transplantation Survivor Study reported in the Journal of Clinical Oncology, McDonald et al found that total-body irradiation in women undergoing autologous or allogeneic blood or marrow transplantation for hematologic malignancies was associated with an increased risk of developing breast cancer.
The retrospective cohort study included patients who underwent blood or marrow transplantation with stem cells from bone marrow, cord blood, or peripheral blood between 1974 and 2014 and survived for 2 or more years. Patients who had received pretransplant chest irradiation or who had a history of breast cancer were excluded.
A total of 1,464 female blood or marrow transplantation survivors—including 788 who had received an allogeneic transplant and 676 who had received an autologous transplant—were included in the analysis. Total-body irradiation was used in 660 patients (46%).
Median follow-up was 9.3 years from blood or marrow transplantation. A total of 37 women developed breast cancer, including 19 who had undergone allogeneic blood or marrow transplantation and 18 who had undergone autologous blood or marrow transplantation. In the entire cohort, the cumulative probability of breast cancer was significantly higher (P = .002) among those exposed to vs not exposed to total-body irradiation, with rates of 2.6% vs 0.3% by age 50, 4.5% vs 1.6% by age 60, and 8.8% vs 3.6% by age 70.
On multivariate analysis, exposure to total-body irradiation was associated with increased risk of breast cancer among both allogeneic blood or marrow transplantation survivors (hazard ratio [HR] = 3.7, P = .03) and autologous blood or marrow transplantation survivors (HR = 2.6, P = .048).
On multivariate analysis, pretransplant exposure to alkylating agents was associated with increased risk of breast cancer among autologous blood or marrow transplantation survivors (HR = 3.3, P = .05) but not among allogeneic blood or marrow transplantation survivors (HR = 0.8, 95% confidence interval [CI] = 0.2–2.6).
Compared with the general population, exposure to total-body irradiation among individuals younger than 30 was associated with significantly increased risk of breast cancer among both allogeneic blood or marrow transplantation survivors (standardized incidence ratio [SIR] = 4.4) and autologous blood or marrow transplantation survivors (SIR = 4.6). The cumulative probability of developing breast cancer among those exposed to total-body irradiation before age 30 was 1.0% by age 40 and 13.9% by age 50.
The investigators concluded, “The association between [total-body irradiation] and subsequent breast cancer, especially among those exposed at a young age, as well as pre[transplant] exposure to alkylating agents, should inform breast cancer screening for early detection.”
Smita Bhatia, MD, MPH, of the Institute for Cancer Outcomes and Survivorship, School of Medicine, University of Alabama at Birmingham, is the corresponding author for the Journal of Clinical Oncology article.
Disclosure: The study was supported by grants from the National Cancer Institute and Leukemia & Lymphoma Society. For full disclosures of the study authors, visit ascopubs.org.The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.