Abstract book - ESTRO meets Asia

S101 ESTRO meets Asia 2018

in radiotherapy has been slow and limited in our setting. This study aims to determine the patterns of recurrence in patients treated with definitive chemo-radiotherapy for cervical cancer and to analyse the factors affecting failures within the radiation portal. Material and Methods From among all the cervical cancer patients registered at our center, records of 509 patients who received radical radiotherapy (combination of external radiotherapy with brachytherapy with or without chemotherapy) during January 2011- December 2012 were reviewed and analysed. The proportion of patients with stage 1, 2 and 3 were 26.9%, 41.1% and 32.1% respectively. Conventional radiotherapy fields were planned after CT Simulation in 62.3%while planning was done on (2D) Simulator in 37.7%. External pelvic radiotherapy consisted of 40-45 Gy with or without nodal boost. Brachytherapy planning was 2D X-ray based in most patients. 60 patients had CT based planning. Most patients had traditional brachytherapy treatment planning with a prescription of 7 Gy to Manchester Point A once every week for 3 weeks. Majority patients (86.4%) were treated with intrauterine tandem and ovoids while 69 patients had intrauterine and vaginal ‘ovoids in tandem’ application. Univariate and multivariate analyses were performed to determine the impact of various tumor and treatment related factors on loco-regional control. Results The actuarial five-year disease free survival probability for the entire cohort was 77.5%. At first follow up, which was at 6 weeks of treatment completion,465(91.3%) patients were in clinical remission. At a median follow up of 58.2 months, 398 patients (78.2%) remained disease free. Among the 111 failures, 56(50.4%) were loco-regional, 42(37.8%) were distal, while 13(11.7%) were both loco- regional and distant. Of the 69 loco-regional relapses, 60 failed within the radiation portal and nine outside. Out of the 69 patients treated with intrauterine and tandem ovoids, 27 experienced central failure. On multivariate analysis the factors predictive of in-field failures were stage of disease (p= 0.007), concurrent chemotherapy (p= 0.03),intrauterine and vaginal ‘ovoids in tandem’ brachytherapy(p= 0.015)and the use of CT Simulation for EBRT planning (p=0.055) Conclusion Loco-regional failure is the dominant pattern of relapse in cervical cancer patients treated with conventional chemo- radiotherapy. Adopting technological advances in radiotherapy for ensuring adequate dose and volume coverage could potentially improve local control. PO-246 Dosimetric and acute toxicity study of VMAT for gynecological cancer: single institution in Thailand W. Thaweerat 1 , P. Dankulchai 1 1 Faculty of Medicine Siriraj Hospital- Mahidol University, Division of Radiation Oncology- Department of Radiology Bangkok, Thailand Purpose or Objective To investigate dosimetric and acute toxicity data in Thai gynecological cancer patients who were treated with volumetric modulated arc therapy (VMAT) technique in single institution. Material and Methods 25 cervical cancer patients, and 18 endometrial cancer patients who were irradiated with VMAT technique were retrospectively included in this study. Target coverage, mean dose, minimum dose and maximum dose were investigated. The delineating organs at risk (OARs) were bowel bag, rectum, bladder and bone marrow. Analyzed dosimetric value were bowel bag V5Gy[cc], V10Gy[cc], V15Gy[cc], V20Gy[cc], V25Gy[cc], V30Gy[cc], V35Gy[cc], V45Gy[cc], V50Gy[cc], Dmean[Gy], rectum V40Gy[%], V45Gy[%], V50Gy[%], bladder V40Gy[%], V45Gy[%],

V50Gy[%], bone marrow V10Gy[cc], V20Gy[cc]. Acute gastrointestinal (GI) toxicity (diarrhea, nausea, vomiting), genitourinary (GU) toxicity (dysuria, urinary frequency) and hematologic toxicity (anemia) were evaluated via retrospective chart review. Correlations between doses and acute toxicity grading were analyzed. Results 25 cervical cancer patients were staged as IB (36%), IIA-IIB (24%), IIIB (36%) and IVB (4%). 18 endometrial cancer patients were staged as IA (22.2%), II (27.8%), IIIA-IIIC2 (50%). The planning target volume (PTV) is 1238.37±419.40 mL. Mean dose, minimum dose and maximum dose are 41.15±6.03 Gy, 58.04±6.06 Gy and 52.29±2.32 Gy respectively. Dose statistics for OARs were described in Table I. 26 patients (60.5%) had diarrhea which 9 of the following (34.6%) had at least grade 2 toxicity. 5 patients (11.6%) had nausea which 2 of the following (40.0%) had at least grade 2 toxicity. 3 patients (7.0%) had vomited which 1 of the following (33.3%) had at least grade 2 toxicity. 10 patients (23.3%) had dysuria. 5 patients (11.6%) had urinary frequency. From 30 patients who had complete blood count result, 25 patients (83.3%) had anemia which 15 of the following (60%) had at least grade 2 toxicity. Acute diarrhea at least grade 2 showed no correlation with small bowel doses but correlated with V50Gy [%] of rectum (63.84 VS 44.48, p=0.038). Acute dysuria was not correlated with bladder dose.

Conclusion The study presented the feasibility of VMAT technique in terms of acute GI, GU and hematologic toxicity. V50Gy of rectum may use to be the predictor of acute diarrhea in gynecological patients treated with VMAT technique.