Abstract
BACKGROUND: Pancreatic mucinous cystadenocarcinoma (MCAC) is a rare malignancy with a poor prognosis when it presents metastases at diagnosis. Due to its very low incidence, there are no clear recommendations for the treatment of advanced disease. Olaparib (an oral PARP inhibitor) has been approved for the maintenance treatment of patients with metastatic pancreatic adenocarcinoma harbouring germline BRCA1/2 mutations. Herein, we report the first case of a germline BRCA1 mutated unresectable MCAC which was effectively treated with olaparib. CASE SUMMARY: A 41-year-old woman, without personal or family history of cancer, was diagnosed with ovarian and peritoneal metastases of MCAC. She underwent 12 cycles of gemcitabine plus oxaliplatin (GEMOX) obtaining a partial response and allowing radical surgery. One year later, local recurrence was documented, and other 12 cycles of GEMOX were administered obtaining a complete response. Seven years later, another local recurrence, not amenable to surgical resection, was diagnosed. She started FOLFIRINOX (oxaliplatin, irinotecan, leucovorin and fluorouracil), obtaining a partial response after 8 cycles. Given the excellent response to platinum-based chemotherapy, BRCA testing was performed, and a BRCA1 germline mutation was detected. She was switched to maintenance olaparib due to chemotherapy-related toxicities and achieved an almost complete metabolic response, with a reduction in the diameter of the lesion, after three months of therapy. CONCLUSION: The current case suggests the beneficial effect of olaparib in BRCA mutated MCAC. However, further studies are required.