Abstract
101 Background: Immune checkpoint inhibitors (ICKi) are highly effective for MSI/dMMR mCRC pts. RECIST1.1 criteria are reported to underestimate response to ICKi. The GERCOR NIPICOL phase II study aimed to evaluate disease control rate (DCR) using RECIST1.1 and iRECIST for MSI/dMMR mCRC pts treated with nivolumab (NIVO) and ipilimumab (IPI). Methods: MSI/dMMR mCRC pts previously treated with fluoropyrimidines (FP), oxaliplatin (OX) and irinotecan (IRI) ± targeted therapies received NIVO 3 mg/kg + IPI 1 mg/kg Q3W for 4 cycles then NIVO 3 mg/kg Q2W until progression or a maximum of 20 cycles. CT-scan tumor assessments were done every 6 weeks during 24 weeks and then every 12 weeks. Primary objective was DCR at 12 weeks (12wDCR) according to RECIST1.1 and iRECIST by central review. Response rates and progression-free survival (PFS) by central review were secondary objectives. A one-stage Fleming design was used with a targeted improvement of 12wDCR from 70% to 85%. Results: Of 57 pts included between Dec 2017 and Nov 2018, 43.9% had received ≥ 3 prior lines including FP (100%), OX (100%), IRI (95.5%), antiangiogenics (57.9%) and anti-EGFRs (45.6%). 17.5% of pts had BRAF mutation and 27.5% Lynch syndrome. Grade 3-4 treatment-related adverse events were reported in 49.1% of pts, mainly hepatitis (12.3%). 12wDCR was 86.0% and 87.7% using RECIST1.1 and iRECIST respectively, with only 1 pseudo-progression (1.8%) observed during the first 12 weeks, and one later. Kappa coefficient between RECIST and iRECIST 12wDCR was 0.92 (95%CI 0.77-1.0). Best observed responses with RECIST1.1/iRECIST were: 2/2 complete responses (3.5/3.5%), 19/19 partial responses (33.3/33.3%), 30/31 stable diseases (52.6/54.4%) and 3/2 disease progressions (5.3/3.5%), with 3 pts not evaluable (cancer-related deaths before first evaluation). Conclusions: Combination of NIVO and IPI in MSI/dMMR mCRC is associated with a low frequency of pseudo-progression and high DCR rate. PFS will be evaluated in Dec 2019, with all pts having completed the predefined 1-year of ICKi therapy. Clinical trial information: NCT033501260.
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