Nivolumab with ipilimumab for MSI-H colorectal cancer with liver metastases.

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e15556 Background: Immune checkpoint inhibitor (ICI) therapy has recently demonstrated durable clinical benefit in patients with advanced mismatch repair deficient (dMMR) colorectal cancer. The aim of this study was to test the combination of nivolumab and ipilimumab in microsatellite instability-high (MSI-H) colorectal cancer patients with oligometastatic liver disease. Methods: Twelve patients with MSI-H mCRC and one prior line of treatment for metastatic disease received nivolumab 3 mg/kg plus ipilimumab 1 mg/kg once every 3 weeks (four doses) followed by nivolumab 3 mg/kg once every 2 weeks until disease progression or discontinuation. The primary endpoint was objective response rate (ORR). Results: At baseline, the patients’ median age was 58 years (range, 51-67 years), and 40.7 % of patients were women. Sites of metastases included liver (89.8%), distant lymph nodes (43.6%), and lungs (9.2%). For all 12 patients (median follow-up was 8.2 months), ORR was 71% (95% CI 46.3–78.6). Of 12 patients enrolled, 4 patients (33%) achieved a partial response, and 5 patients (41%) achieved stable disease. Responses were consistent with the overall population across subgroups including age, Eastern Cooperative Oncology Group (ECOG) performance status, prior adjuvant/neoadjuvant therapy, and mutation status. Two patients (16%) had grade 3–4 treatment-related adverse events. Conclusions: Nivolumab plus ipilimumab demonstrated significant clinical benefit and was well tolerated in patients with MSI-H mCRC. Clinical evaluation of ICIs in first-line metastatic, adjuvant and neoadjuvant settings and in combination with other therapies are ongoing.