ESTRO 2021 Abstract Book

S1069

ESTRO 2021

institute with 45-50Gy EBRT with or without concurrent cisplatin followed by 3-4 fractions of intra-cavitary HDR brachytherapy of 7Gy each. Conventional ICBT planning was performed with dose prescribed to point ‘A’. In patients who underwent CT imaging, apart from ICRU rectum and bladder reference dose points, 2 cc doses to OARs were recorded while in patients with orthogonal X-rays, ICRU bladder and rectum point doses were documented. Patients who had higher bladder and/or rectum doses in the 1st fraction by CT based planning and who needed manual optimization, were planned by CT based planning for subsequent fractions. Propensity matched analysis was done with 1:3 ratio between patients planned with CT-CT and CT-Xray. Factors used for matching were age, stage and concurrent chemotherapy. Mean doses to 2cc of most irradiated part of bladder and rectum were compared by CT planning and these estimates were compared with doses at ICRU bladder and rectal points. Results (3) RESULTS: Two sixty-nine patients were analysed. Median age was 52 years (range 19-80). Majority of patients were FIGO stage IIB (51%) whereas stage IIIB was 32%. No of patients who received concurrent chemotherapy was 226 (88%). CT based planning for first fraction followed by X ray for subsequent fractions was done in majority of patients (n-229), while CT based planning for all 3-4 fractions was done in other patients (n-40). Median Pt A doses delivered were 81.8(69-85) Gy EQD2. Median ICRU bladder and rectal point reference doses were 77(53-102) Gy EQD2 and 70(54-82) Gy EQD2 (a/b=3) (n-210). With a median follow up of 43 months (95% CI,41-45), 3-year OS, DFS, LC was 80%, 80% and 91% respectively. Complete response at 3 months was observed in 83% of patients. 3-year LC was better in patients treated with CT-CT based planning (100%) as compared to that of CT-Xray based planning (91%, p=0.05). CTCAE Grade ≥ 3 proctitis and cystitis were seen in 5 patients (1.8%) and 4 patients (1.5%) respectively. Seven out of nine of these patients were planned with CT-Xray based planning. Conclusion (4) CONCLUSION: CT-X Ray based approach is an acceptable alternative in centres with limited resources. Overall survival was comparable in CT-X Ray and CT-CT groups although local control was compromised who received CT-X Ray brachytherapy. It was observed Xray-based brachytherapy planning overestimates rectum doses and underestimates bladder doses. PO-1300 Stereotactic Body Radiation Therapy for oligometastatic lymph-nodal relapses in gynecological cancer G. Mandurino 1 , A. Fodor 2 , S.L. Villa 1 , S. Baroni 1 , A. Sanchez Galvan 1 , R. Tummineri 3 , P. Pacifico 1 , F. Zerbetto 2 , C.L. Deantoni 2 , P. Mangili 4 , A. Del Vecchio 4 , S. Arcangeli 5 , N.G. Di Muzio 6 1 IRCCS San Raffaele Scientific Institute / University of Milano-BIcocca, Radiation Oncology, Milan, Italy; 2 IRCCS San Raffaele Scientific Institute, Radiation Oncology, Milan, Italy; 3 IRCCS San Raffaele Scientific Institute, Radiation Oncolgy, Milan, Italy; 4 IRCCS San Raffaele Scientific Institute, Medical Physics, Milan, Italy; 5 University of Milano-BIcocca, Radiation Oncology, Milan, Italy; 6 IRCCS San Raffaele Scientific Institute / "Vita-Salute" San Raffaele University, Radiation Oncology, Milan, Italy Purpose or Objective Stereotactic body radiation therapy (SBRT) is becoming the treatment of choice for oligometastatic patients (pts) thanks to its fast delivery, low toxicity and high local control rates. The purpose of this retrospective analysis is to evaluate SBRT for oligometastatic lymph-nodal relapses (LNM) in gynecological cancer pts in terms of local control (LC) and toxicity. Materials and Methods From February 2009 to November 2020, 39 LNM in 26 pts were treated with SBRT. Five LNM of 4 pts were treated with helical Image Guided- Intensity Modulated Radiotherapy (IG-IMRT) to a median dose of 54 (35-63) Gy in 6 (5-10) median fractions prescribed to 95% of the Planning Target Volume (PTV). Thirty-four LNM of 22 pts were treated with robotic SBRT to a median dose of 36 (30-45) Gy in a median of 5 (3-5) fractions prescribed at a median isodose of 79% (68-84%). Seven PTVs (18%) were in the same field of previous adjuvant or salvage radiotherapy performed with IG-IMRT with a median dose of 53.2 Gy. The primary cancer was: ovarian in 11 pts (42.3%), endometrial in 10 pts (38.5%), cervical cancer in 4 pts (15.4%) and fallopian tube carcinoma in 1 patient (3.8%). Seventeen (43,6%) LNM locations were periaortic, 8 (20.5%) mediastinal, 8 (20.5%) pelvic, and 6 (15.4%) in other sites (retroclavicular, supraclavicular, axillary, subcostal and inguinal). Gross tumor volume (GTV) was defined by the fusion of CT and PET/CT images in whole pts. Radiological/Nuclear Medicine imaging and clinical follow up were performed every 3 months. Toxicity was assessed using CTCAE version 4.03 criteria. Results Median follow-up was 18 months (range 2.2–75.4). All pts completed the prescribed treatment. Nine pts (34.6%) presented grade (G) 1-2 acute toxicity, relative to the irradiate site, as follows: diarrhea (n=2, 7.7%), dysphagia (n=1, 3.8%), esophagitis (n=1, 3.8%) and nausea (n=1, 3,8%). No grade ≥3 acute toxicities was observed. One patient presented late toxicity, a G2 rib pain, persistent 28 months after the end of the treatment. A complete response was observed in 33 lesions (84.5%), partial response in 3 lesions (7.7 %) and progressive disease in 3 lesions (7.7 %), respectively. Three pts (11.5%) had local and distant disease progression, while 15 pts (57.7%) had distant disease progression whit local control. Two pts died at a median of 70.8 months after the end of the treatment for progressive disease, and one patient died 8.5 months after the treatment due to a second cancer. Disease Free Survival (DFS) was 12.5 months (1.1-67.2). Conclusion SBRT in oligometastatic lymph nodal relapse of gynecological tumors showed good local control and a good toxicity profile. It might be an appealing alternative to other invasive local therapies as surgery and could delay or avoid systemic therapy. A longer follow up is needed to confirm these results.