Improved disease control with adjuvant therapy for stage IA serous and clear cell uterine cancer: A pooled multi-institutional analysis

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Conference Proceeding

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Int J Radiat Oncol Biol Phys


Purpose/Objective(s): The optimal adjuvant management of Stage IA endometrial cancer with serous or clear cell histology is not well defined. The objective of this study is to explore the role of adjuvant radiotherapy in this population. Purpose/Objective(s): In this ethics board approved study, retrospective review of consecutive patients at six academic centers who underwent hysterectomy for 2009 FIGO Stage IA endometrial cancer with serous or clear cell histology between 2004 and 2015 was conducted. After excluding patients who were upstaged following surgery, descriptive statistics were generated. Time-to event outcomes were calculated using the Kaplan-Meier method, with prognostic factors identified through univariable and multivariable Cox-proportional hazard modeling. Statistical comparisons were calculated in the SAS environment, with significance defined at the 2-sided 0.05 level. Results: A total of 414 patients with a median age of 67 years (range 41-90) met the inclusion criteria. The most common histology was pure serous (64%) followed by mixed (27%) and pure clear cell (9%). Myometrial invasion was identified in 54%. Adjuvant RT was delivered to 47% of patients (pelvic external beam radiotherapy (EBRT) alone 16%; vaginal vault brachytherapy alone 56%; both 28%). One hundred and fourteen patients (34%) received adjuvant chemotherapy with carboplatin/paclitaxel most commonly used (77%). The median follow-up was 2.7 years (range 0-12). The 5-year local control (LC) was as follows: EBRT + brachytherapy 96%, brachytherapy alone 98%, EBRT alone 86% and no radiation 83%. Adjuvant brachytherapy (both alone and in association with EBRT) was associated with improved LC (5-year 96% vs. 84%, log-rank P = 0.0073, adjusted HR 0.36) and disease free survival (DFS) (5-year 79% vs. 71%, log-rank P = 0.0033, adjusted HR 0.70, P = 0.23) but not cancer specific survival (CSS) or overall survival (OS). The 5-year RC was 93% and was not improved by EBRT. Improved regional control was observed when brachytherapy was delivered but not in EBRT subgroup in multivariate analysis (HR 0.16, P = 0.02). Myometrial invasion, lymphovascular invasion, histological subtypes, and the proportion of type II component were not found to be significant prognostic factors for LC. No differential LC benefits with adjuvant RT were observed in subgroups. Adjuvant chemotherapy was associated with improved LC (5-year 94% vs. 84%, HR 0.29, log-rank P = 0.0079) and DFS (5-year 79% vs. 71%, HR 0.47, log-rank P = 0.033), but did not impact RC, DF or CSS. Conclusion: Adjuvant vaginal vault brachytherapy and chemotherapy were independently associated with improved LC and DFS without an observed OS benefit for stage IA serous and clear cell uterine cancer. Prospective study is warranted to clarify the role of adjuvant pelvic EBRT in this setting.





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