ESTRO 38 Abstract book

S808 ESTRO 38

M. Ta 1 , A. Schernberg 1 , P. Giraud 1 , L. Monnier 1 , E. Darai 2 , S. Bendifallah 2 , M. Schlienger 1 , E. Touboul 1 , T. Challand 1 , F. Huguet 1 , E. Rivin Del Campo 1 1 Hôpital Tenon, Radiation Oncology, Paris, France ; 2 Hôpital Tenon, Gynecology, Paris, France Purpose or Objective Adjuvant Whole-Pelvic Radiation Therapy (WPRT) improves loco-regional control for stage I high- intermediate risk to stage III endometrial cancer. Nowadays Intensity Modulated Radiation Therapy (IMRT) tends to replace the standard 3D conformal radiation therapy (3DCRT) technique used in benchmark trials. The objective of this study was to compare 3DCRT versus IMRT in patients with endometrial cancer treated with post- operative WPRT. Material and Methods Patients with FIGO stage I to IIIC2 endometrial cancer treated between 2008 and 2014 in our department with post-operative WPRT were included. The impact of the technique on local control, tolerance, and survival was assessed. Toxicity was graded weekly during radiation therapy, according to the Common Terminology Criteria for Adverse Events (CTCAE) version 3.0. The cumulative probabilities of OS and PFS rates were calculated using the Kaplan-Meier method and compared using a log rank test. Univariate and multivariate analyses were performed using Cox's regression Results Among the 83 patients included, 47 patients were treated with 3DCRT and 36 with IMRT. There were no differences in patient characteristics between the two groups. Most of the women were menopausal (97.6%) with a median age of 68 years (range: 40-86), a myometrial invasion superior to 50% (66.3%) and no vaginal extension (90.4%). FIGO stage III (54.2%) and grade 1-2 (59%) cancers were the most represented in the population. The median dose was 45 Gy (41.4 - 55 Gy). Twenty-four patients (29%) with vaginal extension underwent Low-Dose Rate (LDR) vaginal brachytherapy after WPRT with a median dose at the reference isodose of 15 Gy (range: 10-20 Gy). Median follow-up was 50 months. The 5-year locoregional control and progression free survival (PFS) rates were 94.5% and 68%, respectively. No significant difference was found between the 3DCRT and IMRT groups in terms of survival, with a 5-year-overall survival (OS) rate of 74.6% and 78%, respectively. All locoregional relapses were associated with distant nodal metastasis, except a vaginal relapse. There was a trend towards lymphadenectomy as a prognostic factor of locoregional control but also in overall survival in univariate analysis (Table 1). The multivariate analysis found age over 68, stage > T1, and grade 3 as factors independently associated with shorter PFS and OS (Table 1, Figure 1). Five patients (10.6%) had grade 3-4 acute gastrointestinal (GI) toxicity in the 3DCRT group and two (5.4%) in the IMRT group. One (1.2%) late grade 3 GI toxicity of was observed.

brachytherapy prescription in endometrial cancer. Thus, we conducted a review clinical outcome and toxicity of MRI-based brachytherapy based on post-operative anatomic variation in vaginal cuff (VC) anatomy, which can be visualized using T2W MRI. Material and Methods Retrospective analysis was done in resectable endometrial cancer patients (FIGO stage I-IV) treated with adjuvant MRI-based brachytherapy with or without external beam radiotherapy (EBRT) from January 2013 to December 2016 in King Chulalongkorn Memorial Hospital (KCMH). All patients in vaginal brachytherapy (VBT) alone group received high dose rate (HDR) brachytherapy with 3 fractions of 7 Gy. And the other group received 45-50.4 Gy of tumor-directed EBRT with 2 fractions of 5-7 Gy brachytherapy. Primary outcome was locoregional relapse free survival (LRFS). Secondary outcomes were toxicity, descriptive vagina doses represented by D90 of whole vaginal thickness in EQD2 10 and D2cc doses of bladder and rectum in EQD2 3 . Results Ninety-five patients and 218 brachytherapy plans were included in the analysis. 22 patients were treated with VBT alone and 73 patients received EBRT with VBT. Median age was 58 years old (IQR 52-72). Atypical forms of vaginal shape in MRI was found in 15 patients (16%). Median follow-up time was 40 months (range 23-50). No locoregional relapse was found in VBT alone group at 3 years. 1-yr, 2-yr and 3-yr LFRS in EBRT with VBT group were 93%, 90% and 88%, respectively. No grade 3-5 gastrointestinal (GI) and genitourinary (GU) toxicity was observed in both groups. Rate of grade 1-2 GI toxicity were significant lower in the VBT alone group than in EBRT with VBT group [0% (0/22) vs 11% (8/73)]. Rate of grade 1-2 GU toxicity was not different in both groups [4.5% (1/22) vs 4.2% (3/73)]. Mean D90 doses of whole vaginal thickness were 32.1 Gy EQD2 10 for VBT alone and 63.9 Gy EQD2 10 for EBRT with VBT. In VBT group, mean D2cc doses for bladder and rectum were 29.1 Gy EQD2 3 and 28.0 Gy EQD2 3 , respectively. In EBRT with VBT mean D2cc doses were 57.2 Gy EQD2 3 for bladder and 58.4 Gy EQD2 3 for rectum. Due to few numbers of events, the D2cc doses were insignificantly related to GI and GU toxicity.

Conclusion The MRI-based brachytherapy for determination vaginal wall thickness provides good dose coverage, even in the atypical vaginal shape group. Additionally, this technique gives better chance to avoid adjacent organs. And the clinical results showed the high rate of tumor control and low gastrointestinal and genitourinary toxicities. EP-1492 Comparison of 3DCRT and IMRT in endometrial cancer: efficacy, safety, and prognostic analysis