Young women with primary Hodgkin lymphoma had an increased relative risk of estrogen receptor–positive breast cancer if they received radiotherapy and, irrespective of the type of treatment they got, an elevated risk of ER-negative breast cancer, based on results of a study based on patient records from 12 U.S. National Cancer Institute Surveillance, Epidemiology, and End Results registries.

Of 7,355 women diagnosed with primary Hodgkin lymphoma during 1973-2009 and aged 10-39 years, 377 patients subsequently were diagnosed with breast cancer at a mean age of 45 years; 57% of the cancers were ER positive, 34% were ER negative, and 9% had unknown/borderline ER status, Diana R. Withrow, PhD , and her colleagues from the radiation epidemiology branch, division of cancer epidemiology and genetics, National Cancer Institute reported in JAMA Oncology.

Survivors of Hodgkin lymphoma had a greater relative risk of ER-negative (standardized incidence ratio, 5.8; 95% confidence interval, 4.8-6.9) than ER-positive breast cancer (SIR, 3.1; 95% CI, 2.7-3.5; P less than .001 for the difference), the researchers wrote.

For ER-positive disease, the increased SIR was observed only among women who had received radiotherapy for their Hodgkin lymphoma (SIR, 3.9; 95% CI, 3.4-4.5). In this group, the SIR for ER-positive disease was lower in the chemotherapy than in the no/unknown chemotherapy group (P = .04), said the researchers.

The authors acknowledged that lack of information on patient risk factors such as family history, reproductive factors, and hormone therapy, as well as detailed treatment information such as radiotherapy dose, fields, specific chemotherapeutic agents, and subsequent therapy is a limitation of the current study. Further research, including comprehensive treatment records, will lead to a better understanding of the association between treatment and breast cancer subtype in these patients, the researchers concluded.

None of the study authors reported any conflicts of interest.

SOURCE: Withrow D et al. doi: 10.1001/jamaoncol.2017.4887 .