Association Between Breast Cancer Recurrence With Immunosuppression In Immune-Mediated Disease: A Cohort Study.

e13042Background: Breast cancer recurrence may be promoted by immunosuppression due to decreased immune surveillance. Among patients with immune-mediated disease and previously treated breast cancer, we examined rates of breast cancer recurrence with use of methotrexate, thiopurines, and anti-TNF therapy. Methods: Three retrospective cohort studies within Medicare (2000-2012) included women with rheumatoid arthritis or inflammatory bowel disease who completed surgery for primary breast cancer. Recurrent or second primary breast cancers beyond 365 days from initial surgery were identified. Separate Cox regression models examined risk of cancer recurrence with use of methotrexate, thiopurines, and anti-TNF therapy after surgery, each compared to no use. Analyses were matched on type of breast surgery, and receipt and type of adjuvant therapy. Results: Across all medication groups, 107 women developed breast cancer recurrence during 5,196 person-years. Incidence rates were 20.3 and 19.6 per 1,000 person-year...