Characteristics and outcomes of women with adenocarcinoma versus squamous cell carcinoma of the vulva: A Japanese Gynecologic Oncology Group study

Objective: Studies on vulvar adenocarcinoma are lacking. Thus, we aimed to compare the characteristics and survival outcomes between vulvar adenocarcinoma and squamous cell carcinoma (SCC).

Methods: This was a preplanned sub-analysis of a previously organized nationwide retrospective observational study in Japan conducted between 2001 and 2010 (JGOG-1075S). Surgically treated women with stage I-IV vulvar invasive adenocarcinoma were compared to those with SCC. Multivariable analysis was performed to identify patient and tumor characteristics related to adenocarcinoma. Inverse probability of treatment weighting was used to balance the background differences, and a Cox proportional hazards regression model was fitted to estimate the effect of the histological type on survival.

Results: Forty-eight women with adenocarcinoma were compared with 537 women with SCC. On multivariable analysis, women with adenocarcinoma were younger (median age, 64.5 vs. 70 years, adjusted odds ratio [OR] per age 0.975, 95% confidence interval [CI] 0.955-0.995, P = 0.016) and had higher positive surgical margin rates (31.2% vs. 18.4%, adjusted OR 2.376, 95% CI 1.188-4.754, P = 0.014) than those with SCC. However, according to the weighted model, the survival outcomes were comparable (hazard ratio for progression-free survival, 1.088, 95% CI 0.740-1.601, P = 0.667 and hazard ratio for overall survival, 1.008, 95% CI 0.646-1.573, P = 0.973). Similar associations were observed when the cohort was stratified by age (≤70 or >70 years), stage (I-II or III-IV), and surgical margin (negative or positive) (all, P > 0.05).

Conclusion: Vulvar adenocarcinoma is characterized by a younger age at diagnosis and higher positive surgical margin rates than SCC, but the survival outcomes are comparable.