[Prostate-Preserving Curative Surgery for Isolated Peritoneal Recurrence with Seminal Vesicle Invasion Following Sigmoid Colon Cancer Resection-A Case Report].

A 61-year-old man presented with bowel obstruction caused by sigmoid colon cancer that was detected during screening. After colonic stenting, laparoscopic sigmoidectomy was performed (pT3N0M0, Stage Ⅱa). Follow-up CT performed 2 years later revealed a nodular lesion anterior to the rectum. MRI and PET-CT confirmed peritoneal recurrence invading the rectum and bilateral seminal vesicles. Neoadjuvant chemotherapy comprising 5 courses of mFOLFOX6 plus bevacizumab reduced the tumor size from 19 × 12 mm to 11 × 7 mm. Although total pelvic exenteration was initially considered, tumor shrinkage ultimately enabled prostate preservation. Robot-assisted laparoscopic low anterior resection with bilateral seminal vesicle resection and a diverting stoma was performed. The patient's postoperative course was uneventful, allowing discharge on postoperative day 10. Pathological examination confirmed negative margins, indicating curative resection. This case suggests that chemotherapy-induced tumor shrinkage may facilitate organ-preserving surgery in patients with advanced recurrent colorectal cancer.