Influence of radiation modality and nodal dissection on survival in high-risk early-stage endometrial cancer.

Abstract

5027 Background: A recent randomized trial (PORTEC 2) reported preliminary equivalence of adjuvant whole pelvic radiotherapy (WPRT) with vaginal brachytherapy (VB) in FIGO stage I endometrial cancer with high risk factors. However grade 3 cancers with > 50% myometrial invasion were excluded from this trial, and no nodal dissections (LND) were performed. We wished to determine, by analysis of the SEER registry, the effect of WPRT, VB and LND had on overall survival (OS) in this highest risk subset of stage I cancers. Methods: The SEER registry was queried for grade 3 endometrial cancers with > 50% myometrial invasion undergoing hysterectomy as primary treatment from 1998-2006; we excluded those for whom information about LND and adjuvant radiotherapy were not recorded. Survival analysis was performed via the Kaplan Meier method and the log rank test. Results: 1,941 patients were identified. Median follow up was 45 months; 5 yr OS was 63.6%. LND was performed in1318 (68%). No RT was delievered in 723 (37%), 145 (7.5%) received VB, 744 (38.3%) WPRT, and 329 (17%) WPRT plus VB. LND was associated with increased 5 yr OS (68.8% vs. 54.1%, p < 0.001). Women who did not undergo LND had higher 5 yr OS when they received adjuvant WPRT (60.6%) or WPRT + VB (59.7%) compared to treatment with VB alone (37.5%) or no RT (48.3%, p ≤ 0.002 for all comparisons). Women who underwent LND had higher 5 yr OS following VB alone (79%), WPRT (70%), or WPRT +VB (71.6%), as compared to no RT (63.7%, p ≤ 0.002 for all comparisons). Conclusions: Adjuvant radiotherapy and lymph node dissection are associated with improved overall survival in grade 3 endometrial cancers with > 50% invasion in the SEER registry. WPRT appears to be superior to VB alone in the setting of no LND; this difference and the improved survival of women who underwent LND are likely related in part to the existence of occult nodal metastases in the group without LND. No significant financial relationships to disclose.