A good response to nivolumab in a patient with heavily pre-treated KRAS mutant invasive mucinous adenocarcinoma

Abstract

Background. Invasive mucinous adenocarcinoma (IMA) is an adenocarcinoma variant that shows a strong correlation with the KRAS mutation. In addition, IMA is often without an EGFR mutation and shows a poor tumor response to anticancer chemotherapy. Nivolumab is an immune checkpoint inhibitor that is specific for programmed death 1 and is reported to be effective in prolonging the overall survival in cases of KRAS mutation-positive non-small-cell lung cancer. We herein report a case of KRAS mutation-positive IMA with a good response to nivolumab. Case. A 60-year-old man was admitted to our hospital because of sputum. He was diagnosed with adenocarcinoma (cT3N0M0 stage IIB). A month later, he underwent right lower lobectomy. Two months later, he had tumor recurrence and was treated with a combination of carboplatin and pemetrexed for 6 cycles, followed by maintenance therapy with pemetrexed for 3 cycles. After disease progression, he received albumin-bound paclitaxel as second-line therapy for 12 cycles and docetaxel as third-line therapy for 2 cycles. After disease progression, a transbronchial lung biopsy was performed, which revealed KRAS mutation-positive IMA. The patient received nivolumab as fourth-line therapy. A partial response was maintained after receiving nivolumab for 14 cycles. Conclusion. Nivolumab may be an effective treatment for IMA after determining the KRAS mutation status.