Three-target treatment combined with surgery for BRAF V600E-mutant colon cancer with peritoneal metastasis: a case report

Background: BRAF V600E-mutant advanced colon cancer with peritoneal metastasis is associated with a poor prognosis. Surgery is not recommended by current guidelines, and there are few cases demonstrating the efficacy of targeted therapy combined with surgery in such patients. In the era of precision medicine, we apply aggressive surgery after successful conversion of triple-targeted drugs to prolong survival and provide a clinical basis for the treatment of such patients. Case Description: A 72-year-old male patient presented with abdominal distension and changes in bowel habits was admitted to the Department of Oncology, Shanxi Provincial People's Hospital. The patient was diagnosed with advanced ascending colon adenocarcinoma with peritoneal metastasis after relevant examinations such as abdominal enhanced computed tomography and tests of tumor markers. Later, further genetic testing was performed suggesting BRAF V600E mutation. We treated the patient with firstline three-target therapy (dabrafenib + trametinib + cetuximab). Repeat abdominal enhanced computed tomography after 6 weeks of three-target therapy revealed the disappearance of peritoneal metastases. Subsequently, after 3 months, the patient underwent resection of the primary lesion and removal of greater omental metastases. Three-target therapy continued after surgery until 4 months post-operation. However, carbohydrate antigen 199 was significantly increased at 9 months after medication discontinuation, and returned to normal after 4 months of re-initiation of three-target therapy. The three-target therapy was further adjusted to two-target therapy (dabrafenib + cetuximab) based on the results of circulating tumor cells, and the tumor markers are now normal. Conclusions: Patients with BRAF V600E colon cancer combined with peritoneal metastases are treated with targeted drug conversion therapy, and aggressive surgery may prolong survival depending on the conversion effect. Continued maintenance therapy after surgery may play a role in preventing recurrence.