Prognosis of patients with liver single-organ metastases: Updated survival results of BBCAPX-II.

157 Background: Although immunotherapy has changed the treatment strategy for many cancers with great success, patients with microsatellite stable (MSS) and RAS-mutant metastatic colorectal cancer (mCRC) especially with liver metastases have a low response rate to immunotherapy. Sintilimab plus bevacizumab and CapeOX (BBCAPX) has proved its efficacy and safety in above unresectable mCRC patients (1). Here, we report subgroup analysis of updated survival results of this single arm, open-label, phase 2 trial. Methods: Eligible patients were histologically confirmed unresectable metastatic colorectal adenocarcinoma by multidisciplinary team, and had RAS gene mutation and confirmed MSS status. All patients received treatment with sintilimab plus bevacizumab, oxaliplatin and capecitabine of each 21-day cycle. ORR, DCR, PFS, OS, and subgroup analyses based on metastasis site were performed. Results: From April 2021 to December 2021, 25 patients were enrolled. The ORR was 84% and the DCR was 100%. Six (24%) patients including 5 patients with liver single organ metastases underwent surgical treatment and unexpectedly achieved no evidence of disease status. At the data cut-off day (September 13, 2024), patients with liver single organ metastases presented better prognosis. Median PFS was 25.3 months (95% CI, 4.8-NA) in the patients with liver single organ metastases and 11.5 months (95% CI, 4.83-24.3) in the patients with other metastasis. Median OS was not reached in the patients with liver single organ metastases and 35.5 months (95% CI, 9.36-NA) in the patients with other metastasis. The OS rate at 24 months was 72% (95% CI, 56.4-91.9) in FAS. Median OS was not reached in FAS and 35.5 months (95% CI, 11.4-NA) in PPS. 32% patients had at least one grade 3 or 4 TRAEs. No grade 5 adverse events occurred during the study. Conclusions: This study provides a highly promising regimen for patients with RAS-mutant, MSS, unresectable mCRC, especially those with liver single organ metastases. Furthermore, we are launching a phase III, randomized, open-label, multicentric clinical trial (NCT05171660) to further analyze the effects, safety, and prognostic biomarkers of this regimen. 1. Xuefeng Fang et al. ASCO 2022. Clinical trial information: NCT04194359 . PFS and OS results of BBCAPX-II study. Median PFS 6m PFS rate (%) 12m PFS rate (%) Median OS 12m OS rate (%) 24m OS rate (%) Full analysis set (FAS), n = 25 17.9 (95% CI, 8.84-27) 84 (70.8-99.7) 56 (39.6-79.3) NA 76 (61-94.7) 72 (56.4-91.9) Per-protocol set (PPS), n = 19 9.79 (95% CI, 6.44-27.9) 78.9 (62.6-99.6) 42.1 (24.9-71.3) 35.5 (95% CI, 11.4-NA) 68.4 (50.4-92.9) 63.2 (44.8-89) Classified by metastatic organs (FAS, n = 25) Liver single organ metastases, n = 10 25.3 (95% CI, 4.8-NA) 90 (73.2-100) 70 (46.7-100) NA (11.4-NA) 90 (73.2-100) 80 (58.7-100) Other metastases, n = 15 11.5 (95% CI, 4.83-24.3) 80 (62.1-100) 46.7 (27.2-80.2) 35.5 (9.36-NA) 66.7 (46.6-95.3) 66.7 (46.6-95.3)