Impact of adjuvant radiation therapy (RT) on recurrence and survival outcomes in stage IB-IIA endometrial cancer (EMCA) patients with lymph vascular invasion (LVSI)

Abstract

5568 Background: To determine the clinical outcomes of Stage IB-IIA EMCA patients (pts) with LVSI treated with and without adjuvant RT. Methods: We conducted a four-center retrospective study of pts with Stage IB-IIA EMCA who had LVSI. Papillary serous, clear cell histologies, and pts treated with chemotherapy were excluded. Comprehensive staging was not required. Pts were either observed (Obs), received vaginal brachytherapy (Brachy) or external beam therapy ± brachy (EBRT ± B). Results: We identified 128 pts (49 Obs, 30 Brachy, 49 EBRT ± B). 80 pts (62.5%) underwent surgical staging. Median age was 67 yrs and median follow-up was 5.3 yrs. We observed 32 total relapses, 14/49 (28%) in the Obs group, 2/30 (7%) in the Brachy and 16/49 (33%) in the EBRT ± B group. Relapse rates (RR) were similar between staged and unstaged pts. Of Obs pts, 79% of relapses occurred at the vagina. However, relapses occurred distantly in 100% of Brachy and 87.5% of EBRT ± B pts (p=0.11; p=0.014). For grade 1,2 and 3 tumors, RR were 4/28 (14%), 12/54 (22%), and 16/46 (35%) (p>0.05). In grade 1 and 2 tumors, relapse was 70% local and 31% distal whereas the majority of relapses for grade 3 were distal (88%) p<0.001. RR were significantly associated with tumor invasion of the lower uterine segment (LUS) p=0.035. Overall survival (OS) and cancer-related survival were not significantly impacted by adjuvant RT, due to distant failures. However, adjuvant RT improved pelvic control p=0.007. In a multivariate analysis, LUS invasion correlated with OS (p=0.008) while stage, age, tumor grade, myometrial invasion, and RT (p>0.06) were not. Conclusion: Overall RR for stage IB-IIA EMCA pts with LVSI are high (25%). Although adjuvant RT improved pelvic control, it did not impact RR, cancer-related or OS, likely secondary to distant failures. The role of systemic therapy ± RT for early stage EMCA with LVSI should be evaluated, particularly in pts with high grade tumors or involvement of the LUS. Table 1: Relapse rates for Stage Ib-IIa LVS+endometrial cancers Staged (n=80) Unstaged (n=48) Obs n=28 Brachy n=23 EBRT± B n=29 Obs n=21 Brachy n=7 EBRT± B n=20 Stage IB Total 0/3 (0%) 2/14 (14%) 1/8 (13%) 1/12 (8%) 0/4 (0%) 1/6 (17%) Vagina 0 0 0 1 0 1 Pelvic 0 0 0 0 0 0 Distal 0 2 1 0 0 0 Stage IC Total 8/20(40%) 0/6 (0%) 7/15 (47%) 1/6 (17%) 0/2 (0%) 3/12 (25%) Vagina 5 0 1 1 0 0 Pelvic 0 0 0 0 0 0 Distal 3 0 6 0 0 3 Stage IIA Total 1/5 (20%) 0/3 (0%) 3/6 (50%) 3/3(100%) 0/1 (0%) 1/2 (50%) Vagina 1 0 0 3 0 0 Pelvic 0 0 0 0 0 0 Distal 0 0 3 0 0 1 Total Recurrence Total 9/28(32%) 2/23 (9%) 11/29 (38%) 5/21(24%) 0/7 (0%) 5/20 (25%) Vagina 6/9 (67%) 0 1/11 (9%) 5/5(100%) 0 1/5 (20%) Pelvic 0 0 0 0 0 0 Distal 3/9 (33%) 2/2 (100%) 10/11 (91%) 0 0 4/5 (80%) Overall 22/80 (27%) Overall 10/48 (21%) No significant financial relationships to disclose.