Concurrent hyperthermic intraperitoneal chemotherapy and intraoperative radiotherapy with cytoreductive surgery in patients with rectal cancer with peritoneal carcinomatosis.

e15571 Background: Rectal cancer (RC) is often associated with peritoneal carcinomatosis (PC). Hyperthermic intraperitoneal chemotherapy (HIPEC) and intraoperative radiotherapy (IORT) have been shows to reduce recurrence and effectively treat PC across several cancers. However, little evidence is available regarding the concurrent use of HIPEC and IORT alongside cytoreductive surgery (CRS) in the literature. Methods: We retrospectively reviewed the medical records of RC patients with PC who received HIPEC plus IORT during CRS at the King Faisal Specialist Hospital and Research Centre. Demographic data, PC index (PCI), completeness of cytoreduction (CC), and tumor staging were collected. Overall survival (OS) was calculated from the time of surgery until death or last follow-up. Recurrence-free survival (RFS) was calculated from the time of surgery until recurrence or last follow-up. Unadjusted hazard ratios (HR) were used to determine the impact of parameters on OS or RFS. Results: 17 patients were included in our analysis. Basic demographic data can be found in Table 1. The most common operation performed was rectosigmoid resection in 7 (41.2%) patients, followed by low anterior resection in 6 (35.3%). The pT stage was T0 in 1 (5.9%), T4a in 7 (41.2%), and T4b in 9 (52.9%). The pN stage was N0 in 11 (64.7%), N1a in 1 (5.9%), N1b in 2 (11.8%), N1c in 2 (11.8%), and N2b in 1 (5.9%). There was positive resection margin in 2 patients. The PCI was ≤6 in 15 (88.2%), and the CC score was 0-1 in all patients. No patients had intraoperative complications. 12 (70.6%) received mitomycin C, 4 (23.5%) received cisplatin and mitomycin C, and one patient received a reduced dose of mitomycin C due to old age. 2 (11.8%) patients received two doses of IORT. 11 (64.7%) patients had postoperative complications, of which all were Clavein-Dindo grades 1-3b. Recurrence occurred in 11 (64.7%). The median OS was not reached, and the median RFS was 12 months. There were no parameters associated with OS. Male gender (HR: 7.7, 95% CI: 1.4-57.3), pM1 (HR: 4.5, 95% CI; 1.2-18.1), and perineural invasion (HR: 6.5, 95% CI: 1.2-49.3) were associated with poor RFS in univariate analysis. Conclusions: Incorporating HIPEC and IORT into CRS may be an effective treatment strategy for RC patients. Presence of distant metastasis and perineural invasion can be predictors of rapid recurrence. [Table: see text]