Impact of the new FIGO 2009 staging classification for vulvar cancer on prognosis and stage distribution

Objective: In 2009, FIGO modified staging of vulvar cancer - the performance of the new classification relative to the prior system has not been assessed. We sought to investigate the impact of the 2009 FIGO vulvar cancer staging system on stage distribution and prognostic ability of the 2009 sub-stage classifications in a large cohort of uniformly staged cases with long-term followup. Methods: Patients undergoing surgery for vulvar cancer were identified from 2 institutions (Mayo Clinic and Medical University, Gdansk, Poland) using a similar surgical approach. Inclusion criteria required primary surgery for invasive vulvar cancer for cases with > 1 mm invasion with complete inguinal/femoral lymphadenectomy. The technique of inguinofemoral node dissection used in both institutions was designed to remove both superficial and deep inguinofemoral nodes. A retrospective review was performed and all cases were assigned stage using the 1988 and 2009 FIGO systems after reviewing pathology slides. Cause-specific survival (CSS, death due to cancer) was estimated using the Kaplan-Meier method and compared using the Cox proportional hazards model t for the first 10 years after surgery. Result: A total of 468 patients met inclusion criteria. Thirty-one percent (n = 155) were down-staged, and 1 case up-staged using 2009 staging. The new system fails to effectively separate 10-yr CSS for stage I and II cases (p = 0.52), while FIGO 1988 failed to separate stages II and III (p = 0.41). We observed a difference in survival for stage I and II cases based on tumor diameter. For smaller stage II lesion (≤ 4 cm vs. > 4 cm) we observed no difference in survival compared to all stage IB cases (p = 0.25) Considering node positive disease, patients with 2009 FIGO stages ΙΙΙA, ΙΙΙB, and ΙΙΙC were not significantly different in terms of CSS (p = 0.17). However, CSS approached significance between patients with extracapsular vs. intracapsular disease (p = 0.072). For stages IIIA and IIIB (excluding extracapsular spread, IIIC), we observed that the number of positive nodes and diameter of lymph node metastasis were not significantly associated with CSS. When comparing bilateral nodal involvement vs. unilateral cases with at least 2 involved nodes, we found no statistical difference in CSS (p = 0.30). Conclusion: This is the largest cohort study to evaluate the effect and prognostic performance of the new FIGO vulvar cancer staging system. The new staging does not stratify survival between stages I and II and reduces CSS in stage I cases. Our results suggest that lesion size in node negative cases is an important prognostic variable that could be addressed in future staging classifications. Among the node positive cases, the current classification results in slight differences in CSS, primarily between intra- and extra-capsular disease and not according to the number of positive nodes and lymph node metastasis diameter. Finally we observe that bilateral nodal disease does not appear to impact CSS, justifying it being omitted from the 2009 staging system and that separating node positive (2009 stage III) from node negative (2009 stage II) cases is justified.