Clinical course of multiple sclerosis and patient experiences during breast cancer treatment.

Background: Over one-third of multiple sclerosis (MS) patients are post-menopausal women, the primary demographic affected by breast cancer. After breast cancer diagnosis, there is little information about patients' clinical experiences with both diseases.

Objective: Utilize a case series of MS patients diagnosed with breast cancer to characterize oncologic and MS trajectories, and generate novel insights about clinical considerations using qualitative analysis.

Methods: A single-center retrospective review was performed on medical record data of patients with MS and breast cancer. Thematic analysis was used to characterize experiences with the concurrent diagnoses.

Results: For the 43 patients identified, mean age was 56.7 years at cancer diagnosis and MS duration was 16.5 years. Approximately half were treated with MS disease modifying therapy at cancer diagnosis, and half of these subsequently discontinued or changed therapy. Altogether 14% experienced MS relapse(s) during follow-up (with 2 relapses in the first 2 years), with mean annualized relapse rate of 0.03. Cohort Expanded Disability Status Scale (EDSS) scores remained stable during follow-up. Qualitative insights unique to this population were identified regarding immunosuppression use and neurologic symptoms.

Conclusions: MS relapses were infrequent, and there was modest progression during breast cancer treatment. Oncologic outcomes were comparable to non-MS patients with similarly staged cancer.