Deficient mismatch repair and BRAF-V600E-mutated metastatic colorectal cancer responds to nivolumab therapy after progression under bevacizumab plus FOLFIRI

ABSTRACT Nivolumab, a PD-1 immune checkpoint inhibitor, has been demonstrated to be clinically effective in patients with deficient mismatch repair (dMMR) and BRAF-V600E-mutated metastatic colorectal cancer (mCRC). We present the case of an 81-year-old Taiwanese woman with mCRC who responded favorably to nivolumab for 20 months after the failure of bevacizumab plus FOLFIRI (5-fluorouracil, folinic acid, and irinotecan) treatment. The woman visited our institute and received a diagnosis of ascending colon cancer in December 2019. She underwent right hemicolectomy; the pathologic stage was T3N1bM0, stage IIIb. After 7 months, multiple liver metastases had developed and bevacizumab plus FOLFIRI were administered. However, the disease progressed even after targeted therapy plus chemotherapy. Since February 2021, she has received 3 mg/kg nivolumab biweekly and the best objective response has been found to be partial response as per the response evaluation criteria in solid tumors criteria. No severe adverse events have occurred. The patient has received 33 cycles of nivolumab over 20 months without exhibiting eventual tumor progression. Nivolumab could be considered for dMMR and BRAF-V600E-mutated mCRC that has progressed despite treatment with bevacizumab plus FOLFIRI.