ESTRO 2020 Abstract book

S235 ESTRO 2020

radiotherapy after surgery at first treatment: EBRT 15 patients (8.4%), VBT 4 (2.2%), EBRT and VBT 5 (2.8%). EBRT dose range at first treatment was 48.6-50.4 Gy, HDR-VBT dose range was 10-36 Gy. Mean time from diagnosis to recurrence was 30 months. Mean age at the treatment of the recurrence was 68 years (45-87). We staged relapses according to the Perez modification of FIGO classification of primary vaginal carcinoma. 82 relapses (45.9%) were pelvic mass extended to vagina, 95 (53%) were vaginal (50 limited to the dome and 45 with extension to the mid and/or lower third), 2 (1.1%) were centropelvic. Diameter range 1-6.6 cm. 103 recurrences (57.6%) were treated with a combination of pelvic EBRT (mean dose 45 Gy, range 36 - 60 Gy) and HDR-VBT (mean 25 Gy, range 15 - 30 Gy), 48 cases (26.8%) with HDR-VBT alone (mean 40 Gy, range 35 - 45 Gy) and 5 cases (2.8%) with EBRT alone (mean 60 Gy). Five patients (2.8%) were treated with surgery and VBT, 2 patients (1.1%) with CTH and VBT, 10 patients (5.6%) with surgery followed by EBRT and VBT, 2 patients (1.1%) with a combination of all these approaches. Toxicity was scored according to the CTCAE 4.3. Patients characteristics are shown in the Table.

Conclusion Salvage EBRT and/or HDR-VBT is effective and safe in the treatment of vaginal and pelvic relapses of endometrial cancer. It shows excellent LC, good DFS. OS appears to be related to age and distant metastasis. Second relapses are rare and can be re-treated with further VBT. Grade 4 toxicities are rare even in pre-irradiated patients. Identifying patients at higher risk for a second recurrence or distant metastases is required in order to tailor their treatment.

Results Mean follow up was 70 months (4 - 256). The 120, 180 and 240 months LC rates were 79%, 77% and 77% and DFS rates were 58%, 56%, 56% respectively. We achieved a clinical and radiological complete response in 177 patients (95.5%). In 32 patients (18%) a second recurrence was identified and a third recurrence occurred in 12 patients (6.7%). 16 second relapses were retreated with further VBT and 6 achieved a new CR. Metastases rate was 29%. Treatment was well tolerated. Acute GU G1-G3 toxicity 21 cases (12.1%) and acute GI G1-G3 toxicity 21 cases (12.1%). The major pattern of late toxicity was G1-G3 vaginal stenosis (63 patients, 35.2%). Three developed necrosis of the mucosa (G4) of the inferior third of the vagina, resolved after medical therapy.

Poster Highlights: Poster highlights 14 PH: MRI only planning

PH-0406 An IPEM international survey of MRI use for external beam RT treatment planning R. Speight 1 , M. Tyyger 1 , M.A. Schmidt 2 , G.P. Liney 3 , R.I. Johnstone 4 , C.L. Eccles 5 , M. Dubec 6 , B. George 7 , A. Henry 1 , T. Nyholm 8 , F. Mahmood 9 , J. Korhonen 10 , R. Sims 11 , R.H.N. Tijssen 12 , F. Vanhoutte 13 , S. Busoni 14 , T. Lacornerie 15 , H. McCallum 16 1 Leeds Cancer Centre, Leeds Teaching Hospitals NHS Trust, Leeds, United Kingdom ; 2 Royal Marsden NHS Foundation Trust and Institute of Cancer Research, Cancer Research UK Cancer Imaging Centre, London,