A multicenter analysis of adjuvant therapy after surgery for stage IIIC endometrial adenocarcinoma: A Korean Radiation Oncology Group study (KROG 13-17).

Objective: To investigate whether combined chemoradiotherapy (CTRT) confers a benefit for survival outcome over radiotherapy (RT) alone after primary surgery in patients with FIGO stage IIIC endometrial adenocarcinoma.

Methods: We conducted a multicenter retrospective study of patients with surgical stage IIIC endometrial cancer from 1990 to 2011. Adjuvant RT alone was performed in 85 patients (40.3%) and adjuvant CTRT in 126 patients (59.7%). Disease-free survival (DFS) and overall survival (OS) were analyzed using Kaplan-Meier method and Cox proportional hazards model.

Results: Stage IIIC1 and stage IIIC2 accounted for 63% and 37%, respectively. FIGO IIIC2 had a higher recurrence rate than FIGO IIIC1 (38.5% vs. 29.3%, p=0.172). Five-year OS and DFS were lower in FIGO IIIC2 than FIGO IIIC1 (85.1% vs. 76.9%, p=0.417; 71.0% vs. 59.2%, p=0.108, respectively). Eighteen patients (13.5%) in stage IIIC1 developed PALN recurrence, whereas only one (3.3%) in stage IIIC2 had PALN recurrence (p=0.001). In multivariate analysis, predictors of DFS were parametrial invasion (HR, 3.49; 95% CI, 1.83-6.64; p<0.001), higher grade (HR, 2.78; 95% CI, 1.31-5.89; p=0.008), and >3 positive pelvic nodes (HR, 1.84; 95% CI, 1.11-3.05; p=0.019). Combined CTRT did not affect DFS or OS in IIIC1 and IIIC2 compared with RT alone.

Conclusion: CTRT showed comparable survival outcome to RT alone. Half of relapses (46%) in stage IIIC1 occurred in PALN region, whereas relapse in stage IIIC2 primarily occurred in distant metastasis (90%). Future randomized studies are needed to determine which subgroup may be most likely to benefit from CCRT.