A 52-year-old postmenopausal woman from Delhi presents with abdominal distension and pelvic pain for 3 months. Imaging reveals a 10 cm complex ovarian mass with ascites. CA-125 is 850 U/mL. Staging laparotomy with total abdominal hysterectomy, bilateral salpingo-oophorectomy, omentectomy, and peritoneal biopsies is performed. Histopathology confirms high-grade serous ovarian adenocarcinoma with stage IIIC disease (omental involvement). What is the most appropriate next step in management?