Efficacy and safety of radiation therapy combined with anti-angiogenic agentsand immunotherapy for MSS/pMMR metastatic colorectal cancer: A real-world study.

Abstract

e15559 Background: The combination of anti-angiogenic drugs and immune checkpoint inhibitors (ICIs) can reshape tumor microenvironment, and their effectiveness has been demonstrated in pattients with microsatellite stable (MSS) or mismatch repair profificient (pMMR) metastatic colorectal cancer (mCRC). Radiotherapy (RT) can induce tumor immunogenic cell death, increase infiltration of tumor-infiltrating T lymphocytes and enhance neoantigen expression. Whether the application of RT can further improve the prognosis of pts with MSS/pMMR mCRC receiving anti-vascular drugs and immunotherapy remains to be explored. Methods: We retrospectively identified data on mCRC pts who received anti-angiogenic targeted agents and ICIs after failure of standard therapy at our institution from January 2015 to September 2022. Pts either received RT (RT+TT+IT group) or did not (TT+IT group) during the course of the disease. Baseline characteristics of the groups were compared with the Chi-squared, Fisher's exact, or the independent sample t-test as appropriate. Progression-free survival (PFS) and overall survival (OS) were examined by the Kaplan-Meier method with a log-rank test. Univariate and multivariate Cox regression analysis was conducted to identify prognostic factors for PFS and OS. Results: Of the 89 pts who received anti-angiogenic targeted therapy in combination with ICIs, 43 (48.3%) received RT and 46 (51.7%) did not. All pts were MSS/pMMR. The objective response rate (ORR) of the RT+TT+IT and TT+IT groups was 18.6% (8/43) and 10.9% (5/46) and the disease control rate (DCR) was 83.7% (36/43) and 67.4% (31/46) (both p > 0.05), respectively. The median PFS time was slightly higher in the RT+TT+IT group than in the TT+IT group (5.0 vs. 4.3 months, p = 0.065). In addition, the PFS of RT sequential/simultaneous TT+IT was superior to TT+IT sequential radiotherapy (RT→IT+TT vs. RT-IT+TT vs. IT+TT→RT: median 7.5 vs. 6.1 v.s 3.8 months, p = 0.004). The median OS of RT+TT+IT group was significantly better than that of TT+IT group (15.2 vs. 7.2 months, p = 0.026). Application of RT appeared to be most benefificial in pts aged 56 or younger, advanced stage of initial diagnosis, metastatic lesions involving ≥2 organs, primary lesion not resected, RAS mutations. Cox multivariate regression analysis showed that the number of anti-angiogenic agents plus ICIs cycles > 4 was an independent prognostic factor for OS. No treatment-related deaths were reported, and radiation pneumonia occurred in one patient in the combined radiotherapy group in a manageable manner. Conclusions: The addition of RT during the course of disease can significantly improve the survival benefit of MSS/pMMR mCRC pts treated with anti-angiogenic drugs combined with ICIs posterior line therapy.