ESTRO 2023 - Abstract Book

S627

Monday 15 May 2023

ESTRO 2023

(HRCT) scan, symptoms and clinical findings. HRCT was done pre-radiation therapy and at 24 months. Fibrosis was graded according to the EORTC/RTOG scale. The secondary end points were loco regional and distant failure. Results Between December 2008 to February 2017, 259 women were randomized to receive either concurrent (N=129) or sequential (N=130) tamoxifen. The patient, tumour and treatment characteristics were well balanced between the 2 arms. Forty two patients were excluded from the final analysis- 15 lost to follow up at 24 month time point, 14 developed metastasis, 7 missed the HRCT scan and 4 scans were not retrievable due to technical error. Of the 217 patients, 103 were in the concurrent arm while 114 were in the sequential arm. All the patients scored Grade 0 at baseline HRCT scan before RT. Of 217 patients, 77 (35.48%) had evidence of pulmonary changes between the baseline scans and 24 months after RT. RTOG ≥ Grade II toxicity was observed in 13 (12.6%) patients in the concurrent arm while it was 9 (7.9%) patients in sequential arm (p=0.249). Twenty two percent of patients with CLD >2 cm developed ≥ Grade II fibrosis vs. only 5.7% in patients with CLD <2 cm (p=0.0001). There was no difference in the lung toxicity amongst BCT and MRM patients. The median follow up of the entire cohort was 74 months (inter quartile range 37-110 months). The 5 year locoregional control was 90.4% in the concurrent arm while it was 88% in the sequential arm (p=0.72). The 5 year distant failure free survival was 68% in the concurrent arm while it was 66% in the sequential arm (p=0.55). Conclusion Concurrent administration of tamoxifen does not lead to increase in the pulmonary fibrosis in hormone positive women receiving postoperative adjuvant radiotherapy for breast cancer. Hence, Tamoxifen can be safely administrated concurrently with postoperative radiation therapy OC-0761 CORE - Standard of care +/- stereotactic body radiotherapy for oligometastases - primary results V. Khoo 1 , A. Kirby 2 , M. Ahmed 3 , M. Dewan 4 , N. Van As 5 , K. Franks 6 , M. Hawkins 7 , S. Jain 8 , P. Ostler 9 , I. Syndikus 10 , A. Tree 2 , F. Foroudi 11 , D. Pryor 12 , K. Aitken 13 , E. Miles 14 , R. Patel 14 , F. McDonald 5 , S. Patton 15 , D. Price 16 , C. Toms 4 , L. Kilburn 4 , N. Iles 4 , Z. Gurreebun 4 , E. Hall 4 , O.B. of 17 1 The Royal Marsden NHS Foundation Trust, Urology, London, United Kingdom; 2 The Royal Marsden NHS Foundation Trust and The Institute of Cancer Research, Radiotherapy and Imaging, London, United Kingdom; 3 The Royal Marsden NHS Foundation Trust, Radiotherapy, London, United Kingdom; 4 The Institute of Cancer Research, Clinical Trials & Statistics Unit, London, United Kingdom; 5 The Royal Marsden NHS Foundation Trust, Clinical Oncology, London, United Kingdom; 6 Leeds Teaching Hospital, Clinical Oncology, Leeds, United Kingdom; 7 University College London, Medical Physics and Biomedical Engineering, London, United Kingdom; 8 Northern Ireland Cancer Centre, Belfast Health and Social Care Trust, Clinical Oncology, Belfast, United Kingdom; 9 Mount Vernon Cancer Centre, Clinical Oncology, Northwood, United Kingdom; 10 Clatterbridge Cancer Centre NHS Foundation Trust, Clinical Oncology, Wirral, United Kingdom; 11 University of Melbourne, Radiation oncology, Melbourne, Australia; 12 Princess Alexandra Hospital, Radiation Oncology, Brisbane, Australia; 13 The Royal Marsden NHS Foundation Trust and The Institute of Cancer Research, Clinical Oncology, London, United Kingdom; 14 Mount Vernon Cancer Centre, National Radiotherapy Trials Quality Assurance Group, Northwood, United Kingdom; 15 Health and Social Care Board, Service User and Patient Advocate, Belfast, United Kingdom; 16 Patient and Public Representative, Patient and Public Representative, Solihull, United Kingdom; 17 The CORE, Trial Management Group, London, United Kingdom Purpose or Objective It has been hypothesised that successful ablation of oligometastatic disease (OMD) may improve survival outcomes. Stereotactic body radiation therapy (SBRT) is an advanced radiotherapy technique that can deliver ablative doses to OMD. Previous studies have shown SBRT is safe & effective in locally controlling disease in this setting, but there are few randomised data to allow evaluation of the true benefit of adding SBRT to standard of care (SOC) therapy. CORE, a phase 2/3 trial, aimed to demonstrate 1) feasibility of recruitment, 2) study deliverability in a multicentre setting & 3) activity of SBRT based on progression-free survival (PFS). If all three aims were achieved the trial would be expanded into parallel tumour-site specific phase 3 trials. Materials and Methods CORE (NCT02759783) randomised (1:1) patients (pts) with breast, prostate or non-small cell lung primary cancer & ≤ 3 metachronous OMD sites, who are systemic therapy naïve in the metastatic setting, to SOC +/- SBRT. SBRT dose & fractionation was dependent on OMD site. SOC was declared pre-randomisation & could include chemotherapy, biological therapy, hormone therapy or observation at investigator’s discretion. Palliative radiotherapy could also be given in SOC only arm. Primary endpoint was PFS (all 3 primary disease site cohorts analysed together in ITT population). For phase 2, a sample of 242 pts was required based on a median PFS estimate of 16 months for SOC, 80% power, alpha 0.2 (1-sided; signal finding), hazard ratio (HR)=0.75 & 5% lost to follow-up. A minimum of 50 pts per cohort was targeted. Results Between 11/2016-02/2019 245 pts were randomised (180 prostate, 40 breast, 25 lung; 121 SBRT+SOC, 124 SOC) from 21 UK & 9 Australian centres. Median follow-up was 42.5 months (IQR: 35.9-48.8). Median age was 69 years; 153 (62%) pts had 1 OMD site at baseline, 92 (38%) had 2+. In SBRT+SOC, 116/121 (96%) received SBRT. 164/245 (67%) pts completed SOC as planned; this proportion differed by treatment group (62% SBRT+SOC vs 75% SOC, p=0.002). Overall PFS (HR=0.79 (95%CI: 0.57-1.09), p=0.16 in favour of SBRT+SOC; median PFS=25.0 months for SBRT+SOC, 19.9 months for SOC. In the per protocol population (n=184; excluding pts who did not have SOC as planned & ineligible pts) PFS HR=0.73 (95%CI: 0.50-1.06); p=0.10. Conclusion Overall, the trial met its phase 2 objectives & identified a PFS signal in favour of SBRT+SOC justifying larger definitive phase 3 randomised trials; although recruitment rate in breast & lung cohorts would suggest a trial re-design is required to ensure timely delivery. Despite lack of level 1 evidence, SBRT has become an accepted treatment option for OMD & despite good recruitment to the prostate cohort in phase 2, the trial did not graduate to phase 3. However, biomarker rich & biologically informed randomised trials are still essential to define the group of pts who benefit from SBRT.