Supplementary Material for: Case Report of Complete Response to Olaparib in a Patient with Breast Cancer Brain Metastases

Introduction: Breast cancer is the second most common cause of central nervous system (CNS) metastases. It has been shown that the median time from breast cancer diagnosis to CNS metastasis is 30.9 months and that the overall median survival after metastasis is extremely poor at 6.8 months. Although treatment options for Erb-B2 Receptor Tyrosine Kinase 2 (ERBB2)-positive breast cancer brain metastasis (BCBM) have been reported, effective treatment options for ERBB2-negative BCBM, which has one of the worst prognoses, are limited. Olaparib is one of the standard treatments for germline BRCA1/2 mutated (gBRCA1/2mt), ERBB2-negative, metastatic, or recurrent breast cancer. However, there is minimal existing evidence to evaluate the efficacy of olaparib in BCBM. Case: In our report, we assessed the case of a Japanese woman in her early 30s, ERBB2-negative, gBRAC2mt-positive BCBM, who achieved a complete response (CR) and prolonged progression-free survival (PFS) of nine months after the initiation of treatment with olaparib. Conclusions: Thus, our case report demonstrated the significant efficacy of olaparib in BCBM treatment. Furthermore, we highlighted the need for more studies to investigate the efficacy of olaparib and explore the efficacy of poly ADP ribose polymerase (PARP)-inhibitors in BCBM.