One vs Three HIPEC Cycles After CRS for Pseudomyxoma Peritonei

The goal of this clinical trial is to compare the efficacy and safety of one versus three sessions of hyperthermic intraperitoneal chemotherapy (HIPEC) after cytoreductive surgery (CRS) for patients with pseudomyxoma peritonei (PMP). The main questions it aims to answer are: * Does receiving three HIPEC sessions lead to better Progression-Free Survival (PFS) and Overall Survival (OS) compared to one session? * What are the differences in postoperative complications (e.g., infection, bowel obstruction, myelosuppression) and organ toxicity (e.g., liver/kidney injury) between the two regimens? * How do the different treatment schedules impact patients' quality of life? Researchers will compare the experimental group (3 HIPEC sessions) to the control group (1 HIPEC session) to investigate the efficacy and safety of the additional sessions. Participants will: * Be randomly assigned to one of two groups: 1. Control Group: Receive only a single intraoperative HIPEC session following CRS. 2. Experimental Group: Receive two additional HIPEC sessions after CRS+HIPEC (on post-operative day 2 and day 4) at reduced drug doses. * Undergo scheduled safety checks for side effects on days 1, 3, 5, 7, and 10 post-HIPEC. * Attend a follow-up visit at 1 month after CRS+HIPEC and, if eligible, receive 6 cycles of standard postoperative chemotherapy. * Attend regular long-term follow-up visits for several years, which will include physical examinations, blood tests (for tumor markers), CT scans, and quality-of-life questionnaires (EORTC QLQ-C30 version 3.0).