Gastrointestinal perforation associated with bevacizumab and palliative radiotherapy.

BACKGROUND: The risk of gastrointestinal (GI) perforation associated with bevacizumab (Bev) in patients undergoing palliative radiotherapy (RT) remains unclear. This study investigated the incidence of GI perforation in colorectal cancer patients treated with Bev and palliative RT. METHODS: We retrospectively reviewed colorectal cancer patients who received Bev and palliative RT involving the GI tract between January 2013 and December 2025. Bev and palliative RT were defined as treatment with Bev within 4 weeks before RT initiation or within 4 weeks after RT completion. RESULTS: A total of 109 patients were analyzed. Bev was administered before RT in 44 patients (40.4%), after RT in 34 (31.2%), and both before and after RT in 31 (28.4%). The most common RT regimen was 8 Gy in a single fraction (38.5%), followed by 20 Gy in 5 fractions (37.6%) and 30 Gy in 10 fractions (21.1%). The median follow-up from RT initiation was 223 days. GI perforation occurred in 3 patients (2.8%; 95% confidence interval [CI], 0.6-7.8%), with a 180-day cumulative incidence of 2.1% (95% CI, 0.4-6.6%). All perforations occurred in the rectum within the RT field; two occurred within the planning target volume and one outside it. Compromised GI wall within the RT field was significantly associated with GI perforation (p = 0.010). CONCLUSION: The incidence of GI perforation was low in colorectal cancer patients treated with Bev and palliative RT. However, caution is warranted when compromised GI wall is present within the RT field.