e15585 Background: A previous phase 1b trial has shown encouraging efficacy of regorafenib plus nivolumab in patients with microsatellite stable/mismatch repair proficient (MSS/pMMR) metastatic colorectal cancer (mCRC). We aimed to evaluate the efficacy and safety of this regimen in Chinese patients in the real world. Methods: We retrospectively identified patients with MSS/pMMR mCRC who received at least one dose of programmed cell death-1 (PD-1) inhibitors plus regorafenib from 5/2019 to 2/2021 in 10 Chinese medical centers. The primary endpoint was overall survival (OS). Secondary endpoints included progression-free survival (PFS), objective response rate (ORR), disease control rate (DCR) and the safety. Results: Fifty-two patients were identified. Liver metastases were presented in 35 patients (67%). A total of 48 patients (92%) received regorafenib plus a PD-1 inhibitor as the third or later line treatment. At the data cut-off, 11 patients (21%) were still on treatment. Other patients terminated treatment because of progressive disease (45%), treatment-related adverse events (TRAEs) (14%) or treatment-unrelated deaths (6%). The median treatment cycle was 3 (range, 1-18). At a median follow-up of 4.9 months, the median OS was 17.3 months (95% CI, 10.2-NR) and the median PFS was 3.1 months (95%CI, 2.5-6.0). Baseline liver metastases were associated with inferior PFS (2.7 versus 6.3 months, p <0.05), but not OS (17.3 months versus NR, p =0.6). Among 38 patients evaluable for response, two patients (5%) achieved partial response, and 17 patients (45%) experienced stable disease as the best response. The DCR was 50% (95%CI, 5.0-NR) and was similar among different PD-1 inhibitors (Table). TRAEs were observed in 30 patients (58%). Fatigue (21%), hand-foot syndrome (19%) and rash (13%) were the most common TRAEs. Eight patients (15%) experienced grade 3-4 TRAEs, including rash (n=3), hand-foot syndrome (n=2), hypertension (n=1), myocardial enzyme elevation (n=1) and visual field loss (n=1). No treatment-related death occurred. Conclusions: The combination of regorafenib plus PD-1 inhibitors was generally tolerated and exhibited potential benefit in terms of OS and DCR. The presence of baseline liver metastases was predictive for shorter PFS but requires further investigation. Disease control rate of different PD-1 inhibitors.[Table: see text]
P-137 Patient baseline characteristics in the PROMETCO study: A real-world, prospective longitudinal cohort on the continuum of care of metastatic colorectal cancer
