Case Report: rectal perforation and Fournier's gangrene after irinotecan in a bevacizumab-exposed, previously irradiated patient

Bevacizumab-associated intestinal perforation and Fournier’s gangrene have been reported separately; however, the potential contribution of residual anti-VEGF exposure prior to subsequent chemotherapy in previously irradiated pelvic tissue remains underrecognized. Radiotherapy causes fibrosis and microvascular injury, bevacizumab impairs healing, and irinotecan-induced diarrhea may exacerbate perforation risk. Deferring DRE, imaging, and surgical consultation in patients with unexplained perineal or buttock pain increases the risk. A 61-year-old man with rectal adenocarcinoma received neoadjuvant chemoradiotherapy followed by total mesorectal excision and ileostomy in March 2024. After adjuvant chemotherapy, surveillance in March 2025 revealed recurrence with pelvic invasion and liver/lung metastases. He received eight cycles of XELOX plus bevacizumab, then bevacizumab maintenance, stopped on 4 March 2026 for rectal hemorrhage. This 22-day interval is shorter than the label-mandated 28-day hold and NCCN-recommended ≥6-week washout for surgery—standards primarily addressing wound healing rather than chemotherapy sequencing. Five days after irinotecan initiation, grade 3 diarrhea developed. He was admitted on 13 April 2026 with diarrhea, left buttock pain; he received empirical ceftazidime plus moxifloxacin. On 14 April, DRE, imaging, and surgical consultation were deferred due to pain. By 18 April, septic shock developed with perineal necrosis and crepitus. CT confirmed Fournier’s gangrene. Emergency debridement with abscess curettage and seton drainage was performed. Fecal diversion was declined. Antibiotics were escalated to meropenem then vancomycin after cultures grew VSEfm . He left the ICU but needed twice-daily dressing changes. Two weeks postoperatively, care shifted to palliation, and he died of multiorgan failure. This case raises the hypothesis that, in previously irradiated tissue, residual bevacizumab exposure at the time of subsequent irinotecan initiation—exacerbated by irinotecan-induced diarrhea and pre-existing rectal mucosal damage—may have contributed to rectal perforation and subsequent Fournier’s gangrene. Notably, while bevacizumab and irinotecan are routinely combined, whether extrapolating surgical washout standards (≥6 weeks) to anti-VEGF sequencing before high-mucosal-toxicity chemotherapy warrants prospective investigation. Unexplained perineal or buttock pain in such patients should trigger urgent clinical evaluation, including DRE when feasible, imaging, and early surgical consultation, to prevent diagnostic delay.