A 48-year-old woman from Mumbai undergoes staging laparotomy for a suspected ovarian mass. Intraoperative findings show a 6 cm left ovarian mass, normal right ovary, no ascites, and normal peritoneal surfaces. Frozen section confirms high-grade serous adenocarcinoma. The surgeon performs left salpingo-oophorectomy and comprehensive staging (omentectomy, peritoneal biopsies, pelvic and para-aortic lymph node sampling). Final pathology shows stage IA disease (tumor confined to left ovary, no capsular rupture, negative lymph nodes). What is the most appropriate next step in management?