Impact of mRNA COVID-19 vaccination on survival in pembrolizumab-treated stage IV colon cancer: A multi-institutional propensity-matched analysis.

Abstract

e15624 Background: Colon cancer remains a leading cause of cancer-related mortality. While immune checkpoint inhibitors (ICIs) like pembrolizumab have revolutionized treatment for advanced microsatellite instability-high (MSI-H/dMMR) colon cancer, methods to further improve survival is needed. Recent data have confirmed the safety of mRNA COVID vaccines in patients on ICIs, with emerging studies in melanoma and NSCLC even suggesting a potential synergistic effect whereby peritherapeutic mRNA COVID vaccines may enhance ICI efficacy and lead to improved survival. However, the clinical impact of this association in colon cancer remains unexplored. This study sought to evaluate whether mRNA COVID vaccination improves survival in patients with stage IV colon cancer receiving pembrolizumab. Methods: A retrospective cohort study was conducted using the TriNetX database. We identified stage IV colon cancer patients treated with pembrolizumab between 12/11/2020 and 01/26/2023. Group 1 (Vaccine) received an mRNA COVID vaccine within ±12 months of their first pembrolizumab infusion; Group 2 (Control) did not. Patients with skin or respiratory malignancies synchronous with colon malignancy were excluded to account for pembrolizumab treatment not targeting colon cancer. Propensity score matching (1:1) was performed based on age, sex, race, and comorbidities (diabetes, hypertension, obesity, heart disease, tobacco use, and liver disease). Primary outcome was median overall survival at 3 years (end date: 01/26/2026). Results: Following 1:1 propensity score matching, 374 patients were included in the final analysis (Vaccine group, n = 188; Control group, n = 186). Kaplan-Meier analysis revealed no statistically significant difference in survival between patients the vaccine group and the control group. Median survival for the vaccine cohort was 879 days, while median survival for the control cohort was not reached. At the end of the 3-year period, survival probability was 43.3% in the vaccine group and 50.4% in the monotherapy group, with a log-rank p-value of 0.308, suggesting that COVID-19 vaccination did not significantly impact survival outcomes in this cohort. Cox proportional analysis revealed no statistically significant difference in survival (HR 1.163; 95% CI 0.870-1.553). Conclusions: In this retrospective cohort study, mRNA COVID vaccination within a year of the first pembrolizumab infusion did not affect survival in stage IV colon cancer. This suggests that previous positive findings regarding vaccination during pembrolizumab therapy in other cancers might not extend to colon cancer. Limitations of our study include our assumption that all stage IV colon cancer patients treated with pembrolizumab were MSI-H due to inherent limitations preventing stratification by MSI-H status on the TriNetX platform.