Updated FIGO Staging for Ovarian Cancer: Key Changes and Clinical Implications
The 2014 FIGO staging system for ovarian, fallopian tube, and primary peritoneal cancer introduced critical subdivisions that improve prognostic stratification and guide treatment decisions, with the most significant changes being the subdivision of stages IC, IIIA, IIIC, and IV, while eliminating stage IIC. 1
Major Structural Changes
Stage IC Subdivisions
The updated classification subdivides stage IC into three prognostically distinct categories 2:
- IC1: Surgical capsule rupture (intraoperative spillage)
- IC2: Pre-operative capsule rupture or tumor on ovarian/fallopian tube surface
- IC3: Malignant cells in ascites or peritoneal washings
This subdivision is clinically meaningful, as stages IC1 showed 5-year survival of approximately 87%, while IC2 and IC3 had lower survival rates of 75-80% 3.
Stage II Modifications
- Stage IIC has been eliminated 1, 2
- Stages IIA and IIB now show similar survival (61% vs 65% 5-year survival) 3
- Metastasis to sigmoid colon is now classified as stage II due to anatomic proximity within the pelvis 2
Stage III Refinements
The most impactful changes occur in stage III disease 1, 2:
Stage IIIA subdivisions:
- IIIA1: Positive retroperitoneal lymph nodes ≤10 mm (formerly some stage IIIC cases)
- IIIA2: Positive retroperitoneal lymph nodes >10 mm or microscopic extrapelvic peritoneal involvement
Stage IIIB: Macroscopic peritoneal metastases ≤2 cm outside the pelvis (with or without positive retroperitoneal lymph nodes)
Stage IIIC subdivisions:
- IIIC1: Pelvic lymph node involvement alone
- IIIC2: Para-aortic lymph node involvement (with or without pelvic nodes), reflecting worse survival 1
Approximately 4.2% of previous stage IIIC patients were down-staged to IIIA2 or IIIB with better prognosis 4. Lymph node involvement must be proven cytologically or histologically 2.
Stage IV Subdivisions
Stage IV is now divided into 2, 5:
- IVA: Malignant pleural effusion (13% 5-year survival)
- IVB: Parenchymal metastases and/or extra-abdominal metastases including inguinal lymph nodes, umbilical deposits, and transmural bowel infiltration with mucosal involvement (13% 5-year survival)
Both substages remain statistically distinct from stage IIIC (22% 5-year survival; P < 0.0001) 3.
Documentation Requirements
The updated system mandates documentation of 2:
- Primary anatomic site: ov (ovarian), ft (fallopian tube), p (peritoneal), X (not assessed)
- Histologic subtype: HGSC (high-grade serous), LGSC (low-grade serous), MC (mucinous), CCC (clear cell), EC (endometrioid)
Critical caveat: There is no stage I peritoneal cancer by definition 2.
Treatment Implications
Early-Stage Disease
The refined staging led to 7.56% more patients with early-stage disease receiving platinum-taxane chemotherapy according to current recommendations 4. High-grade serous carcinoma predominates in both early and advanced stages 4.
Surgical Staging Requirements
Comprehensive surgical staging remains essential and should include 1:
- Bilateral salpingo-oophorectomy
- Hysterectomy
- Omentectomy
- Peritoneal biopsies
- Pelvic and para-aortic lymph node assessment
- Peritoneal washings (results recorded but no longer affect staging) 1
Prognostic Validation
Analysis of 4,036 patients demonstrated that the revised staging adequately reflects survival with clear statistical separation between stages 3:
- Stage IA/IC1: 87% 5-year survival
- Stage IB/IC2/IC3: 75-80% 5-year survival
- Stage IIA/IIB: 61-65% 5-year survival
- Stage IIIC: 22% 5-year survival
- Stage IVA/IVB: 13-14% 5-year survival
Important limitation: With 14 substages (increased from 10), fewer patients populate each category, potentially reducing statistical power for individual substage analysis 3.
Imaging Role
Imaging modalities (CT, MRI, PET/CT) are essential for 1:
- Preoperative assessment of disease extent
- Predicting optimal cytoreduction feasibility
- Detecting supradiaphragmatic disease (stage IVA)
- Identifying parenchymal metastases (stage IVB)
The updated classification improves prognostic accuracy and enables more individualized therapeutic approaches based on refined stage-specific survival data 4, 2.