ESTRO 36 Abstract Book

S390 ESTRO 36 _______________________________________________________________________________________________

IPI). Ipi was administered intravenously at a dose of 3 mg/kg over 90 min every 3 weeks for 4 doses. We treated 120 lesions whit median diameter size of 8 mm (2-42 mm). 67 SRS(dose range 10-24Gy) and 23 SRT(dose range 18- 24Gy). We evaluated the local response according to RECIST criteria. We assessed LC as the sum of CR, PR and SD, IC, and median OS from the date of the SRS/SRT procedure. Results The median follow-up (FU) was 7 months (m) (range 0-26). 55 pts for a total of 109 lesions were evaluable for FU. The median OS for all pts was 9.7 m and the median OS of 52 pts who received Ipi and RT was 10 m vs 9.7 m of 11 pts IPI NO(P=0.82). The median OS for single group was: 9.7 m for NO-IPI, 7.7 m for IPI PRE-RT, 9.7 m for IPI CONC RT and 11.5 m for IPI POST-RT (p=0.95). The 1-year OS was 41% for IPI POST-RT, 32% for IPI PRE-RT, 36% for NO-IPI and 33% for IPI CONC RT . The 1-year LC of all pts lesions was 43.2%, and the 1-year LC of pts who received Ipi+RT was 48% vs 25% of pts NO IPI(p=0.06).The 1-year LC for single group was 72% for IPI PRE-RT, 36% for IPI POST-RT, 25% for NO- IPI and 33% for IPI CONC RT(p=0.08). The 1-year IC of all pts was 40.1%, and the 1-year IC of pts who received Ipi and RT was 41.5% vs 50% of pts NO IPI.

role of Ipi also in the treatment of melanoma pts with BMs and the better sequence with RT.

Poster: Clinical track: Sarcoma

PO-0742 Target delineation conformity in extremity STS within the UK phase II multi-centre IMRiS trial H. Yang 1 , R. Simões 1 , F. Le Grange 2 , S. Forsyth 3 , D. Eaton 1 , B. Seddon 2 1 Mount Vernon Cancer Centre, National Radiotherapy Trials Quality Assurance Group, Northwood, United Kingdom 2 University College Hospital, Sarcoma Unit, London, United Kingdom 3 University College London, Cancer Research UK & University College London Cancer Trials Centre, London, United Kingdom Purpose or Objective Accurate target volume delineation is essential in the use of intensity-modulated radiotherapy, where its role in the treatment of bone and soft tissue sarcoma (STS) is being investigated for the first time within the UK in IMRiS, a prospective multi-centre phase II trial. As part of radiotherapy trials quality assurance, we determined the conformity of volume delineation of an extremity STS benchmark training case in the post- operative setting, and report target outlining variation in relation to the trial protocol. Material and Methods The clinical history, operation/histology reports, pre- operative magnetic resonance imaging and planning scans of the training case were made available to participating clinicians, who submitted outlines based on the protocol. Both first and re-submissions were evaluated by two clinicians, where GTV, CTV_6000 and CTV_5220 were compared to the reference contours. The volumes were quantitatively assessed using Dice Similarity Coefficient , where A and B represent regions of interest. Individual feedback based on trial protocol variations was provided for all submissions. Results There was a total of 25 submissions from 23 centres. Delineation of GTV, CTV_6000 and CTV_5220 were deemed unacceptable according to the protocol in 5(20%), 10(40%) and 5(20%) submissions respectively. The table details the unacceptable variations from the protocol. All unacceptable GTV contours failed to reconstruct the pre-operative disease in its entirety. Incorrect margin expansion constituted the majority of the unacceptable submissions for both CTVs. (DSC) as:

Conclusion Our experience suggests that the combination of Ipi+SRS/SRT in MBMs pts can obtain a better survival with a low toxicity profile related to combined treatment. The high precision of treatment with Cyberknife allows to reduce radiation of organs at risk. The optimal timing of combination Ipi+RT is not clear, but from our experience it would seem to be a benefit of using the Ipi before SRS/SRT on LC. The recruitment of a greater number of pts and a longer follow-up are needed to demonstrate the

The mean DSCs were systematically lower for the unacceptable contours compared to accepted contours for GTV [0.61 (range 0.55–0.66) vs 0.77 (range 0.60–0.81), p<0.001], CTV_6000 [0.75 (range 0.53–0.82) vs 0.82 (range