Primary Peritoneal Cancer Staging and Treatment

Staging System

The International Federation of Gynecology and Obstetrics (FIGO) staging system is used for primary peritoneal cancer, with primary peritoneal cancer classified as Stage II disease, and the Peritoneal Cancer Index (PCI) is used to quantify disease burden for surgical planning 1
The FIGO staging framework classifies primary peritoneal cancer as Stage II, with tumor involving pelvic extension or primary peritoneal cancer 1

The PCI quantifies peritoneal disease burden by dividing the abdomen into 13 regions, with each region scored 0-3 based on lesion size, and a total PCI score ranging from 0-39 2
A PCI score of ≥20 indicates extensive disease burden, while a score of ≤10 indicates limited disease burden suitable for cytoreductive surgery plus HIPEC in selected malignancies 3

Women with primary peritoneal cancer should be treated identically to FIGO Stage III ovarian cancer, with optimal surgical debulking (cytoreductive surgery) followed by platinum-based combination chemotherapy (carboplatin plus paclitaxel) 5, 6, 7, 8
The American College of Obstetricians and Gynecologists and the Society of Gynecologic Oncology recommend evaluation by a gynecologic oncologist prior to treatment initiation, and staging workup including midline laparotomy, peritoneal washings, and assessment of all 13 peritoneal regions for PCI calculation 1, 4

The diagnostic workup algorithm includes CT abdomen/pelvis with IV and oral contrast, plus chest imaging (CT preferred), and tissue diagnosis with immunohistochemistry, including estrogen and progesterone receptors, CK7/CK20 pattern, PAX8, WT-1, and CA-125 level 4, 5, 6
Diagnostic laparoscopy may be considered if imaging is equivocal or to confirm resectability, given its superior sensitivity (85%) versus CT (28-51%) 4

Clinical factors indicating likely suboptimal surgery include age ≥60 years, ASA Physical Status 3-4, and radiologic findings such as retroperitoneal lymph nodes above renal hilum >1 cm, diffuse small bowel adhesions or thickening, and small bowel mesentery lesions >1 cm 2, 4

The National Comprehensive Cancer Network recommends not relying solely on CT imaging to determine resectability, as it significantly underestimates peritoneal disease burden, and not using PCI ≥20 as an absolute contraindication to surgery 4, 9
The European Society for Medical Oncology recommends not adding HIPEC to cytoreductive surgery for primary peritoneal cancer outside clinical trials, as evidence is lacking, and not delaying adjuvant chemotherapy beyond 6-8 weeks post-operatively 2, 9