Response to Vemurafenib in Metastatic Triple-Negative Breast Cancer Harbouring a BRAF V600E Mutation: A Case Report and Electronically Captured Patient-Reported Outcome.

Effective treatment options are still scarce for metastatic triple-negative breast cancers. An increasing interest in the mutational landscape of this disease will facilitate novel therapeutic strategies in a variety of cancers. Here we report the case of a 38-year-old female patient who developed multiple lung metastasis of a triple-negative breast cancer 2 years after the completion of local therapy. When she progressed after two palliative chemotherapy lines and local electroporation, a next-generation sequencing revealed a BRAF V600E mutation for which we initiated therapy with the BRAF inhibitor vemurafenib. Radiological improvement was already evident after 3 months and has been ongoing for 19 months so far with very few side effects, as is demonstrated by electronically captured patient-reported outcomes. To our knowledge, this is the first published case where a BRAF V600E-mutated advanced triple-negative breast cancer was successfully treated with vemurafenib.