Abstract Book

S311

ESTRO 37

5 university hospital and faculty of medicine c.g. carus- tu dresden- national center for tumor diseases dresden, dept. Of nuclear medicine, dresden, germany 6 helmholtz-zentrum dresden - rossendorf, institute of radiopharmaceutical cancer research, dresden, germany 7 university hospital and faculty of medicine c.g. carus- tu dresden- national center for tumor diseases dresden, dept. Of neurosurgery, dresden, germany 8 german cancer consortium german cancer research center dkfz heidelberg- university hospital and faculty of medicine c.g. carus- tu dresden- helmholtz-zentrum dresden - rossendorf, dept. Of radiooncology, dresden, germany 9 german cancer research center dkfz heidelberg- university hospital and faculty of medicine c.g. carus- tu dresden, dept. Of radiology, dresden, germany Purpose or Objective The purpose of the prospective biomarker trial was to investigate the association of high [11C]methionine (MET) tracer uptake before postoperative radiochemotherapy and concurrent temozolomide with time to recurrence in patients with glioblastoma multiforme. Material and Methods Main inclusion criteria were histologically confirmed newly diagnosed glioblastoma multiforme, tumour resection or biopsy, planned radiochemotherapy with temozolomide, surgery - radiochemotherapy interval max. 7 weeks, age ≥ 18 y., ECOG Score ≥ 2, written informed consent. [11C]methionine positron emission tomography/ magnetic resonance imaging (MET-PET/MRI, Philips Ingenuity TF PET/MR) was performed before radiochemotherapy and at each follow-up timepoint thereafter (every 3 months) until tumour recurrence. Radiotherapy (photons or protons) was performed with 2 Gy per fraction to a total dose of 60 Gy using a shrinking field technique. Temozolomide was applied according to clinical standard. A sample size of n = 79 was chosen to detect a significant prognostic association of [11C]-MET levels and time to recurrence with hazard ratio 2.0 and power 90% using a median split. The main hypothesis was that the time to tumour recurrence is longer in patients without postoperative tumour residuum in PET/MRI as compared to patients with tracer accumulation after 101 patients were recruited between 2013 and 2016. At the time of data analysis (01/18), the median follow-up was 14.4 months (range 1.5 months; 46.7 months). With a drop-out of 13 patients (12.7%), 89 patients were evaluable for this first analysis. Of the evaluable patients, 6 patients had biopsy only, 83 patients had partial or total tumour resection. 30 patients showed no residual tumour in the postoperative PET, 59 patients were scored with a MET tracer accumulation at this timepoint. 46 patients had no tumour residuum in the postoperative MRI (T1w with gadolinium contrast enhancement), 43 patients had a residual tumour. With 19.2 months (95%C.I. 16.4; 21.9 months), median time to recurrence was significantly longer for patients without MET accumulation in the postoperative PET/MRI as compared to 6.3 months (3.3; 9.2) for patients with residual accumulation (p<0.001). Similar differences were detected between PET-negative and PET-positive patients for overall survival (median not reached vs. 14.5 months [12.8; 16.2], p=0.001 for no tumour residuum vs. tumour residuum in PET; 21.5 months [16.4; 26.6] versus 14.2 months [11.9; 16.5], p=0.06 for no tumour residuum vs. tumour residuum in MRI). Conclusion First data analysis of this prospective trial confirmed the primary hypothesis of a longer time to recurrence for patients without tumour detection in postoperative MET- PET. The next step is the evaluation of a spatial correlation of the PET-positive volume with the region of surgery. Results

recurrence, as a potential basis for later local radiation dose-escalation trials. OC-0595 FAST-Forward phase 3 RCT of 1-week hypofractionated breast radiotherapy:3-year normal tissue effects A.M. Brunt 1 , J. Haviland 2 , M. Sydenham 2 , A. Al-hasso 3 , D. Bloomfield 4 , C. Chan 5 , M. Churn 6 , S. Cleator 7 , C. Coles 8 , M. Emson 2 , A. Goodman 9 , C. Griffin 2 , A. Harnett 10 , P. Hopwood 2 , A. Kirby 11 , C. Kirwan 12 , C. Morris 13 , E. Sawyer 14 , N. Somaiah 15 , I. Syndikus 16 , M. Wilcox 13 , R. Zotova 17 , D. Wheatley 18 , J. Bliss 2 , J. Yarnold 11 1 university hospitals of north midlands nhs trust, cancer centre, stoke-on-trent, united kingdom 2 the institute of cancer research, clinical trials and statistics unit, sutton, united kingdom 3 the beatson west of scotland cancer centre, department of clinical oncology, glasgow, united kingdom 4 royal sussex county hospital nhs trust, sussex cancer centre, brighton, united kingdom 5 nuffield health cheltenham hospital, department of breast surgery, cheltenham, united kingdom 6 worcestershire acute hospitals nhs trust, directorate of oncology and haematology, worcester, united kingdom 7 imperial college healthcare nhs trust, department of oncology, london, united kingdom 8 university of cambridge, department of oncology, cambridge, united kingdom 9 royal devon and exeter nhs foundation trust, exeter oncology centre, torbay, united kingdom 10 norfolk and norwich university hospital nhs trust, department of oncology, norwich, united kingdom 11 the institute of cancer research and the royal marsden hospital, academic radiotherapy, sutton, united kingdom 12 manchester university hospital nhs trust, department of surgical oncology, manchester, united kingdom 13 independent cancer patients' voice, icpv trials, london, united kingdom 14 guy's and st thomas' hospitals nhs trust, cancer centre, london, united kingdom 15 the institute of cancer research, division of radiotherapy and imaging, sutton, united kingdom 16 clatterbridge cancer centre, radiotherapy, clatterbridge, united kingdom 17 mount vernon hospital, radiotherapy trial qa team, london, united kingdom 18 the royal cornwall hospital nhs trust, sunrise cancer centre, truro, united kingdom Purpose or Objective FAST-Forward aims to identify a 5-fraction schedule of adjuvant radiotherapy delivered in 1 week that is at least as effective and safe as the UK standard 15-fraction regimen after primary surgery for early breast cancer. The primary endpoint is local-regional relapse at 5 years, with normal tissue effects (NTE) important secondary endpoints. Previous breast radiotherapy trials have shown that NTE rates at 3 years predict 5 and 10-year comparisons; NTE results up to 3 years are reported here. Material and Methods The FAST-Forward trial (ISRCTN19906132) randomised patients with invasive carcinoma of the breast (pT1-3 pN0-1 M0) following breast conservation surgery or mastectomy (immediate reconstruction was allowed) to 40Gy in 15 fractions over 3 weeks (control), 27Gy or 26Gy in 5 fractions over 1 week (1:1:1) to whole breast or chest wall. A tumour bed boost of 16Gy in 8 fractions or 10Gy in 5 fractions was given where indicated. NTEs were assessed annually by clinicians, at baseline, 3, 6, 12 and 24 months by patients and from photographs at 2 years compared with a pre-radiotherapy baseline. Clinician and patient assessments used a 4-point scale corresponding to none, mild, moderate, marked; photographic assessments of change in breast appearance were scored as none, mild or marked. Schedules were compared using cross-