ESTRO 2021 Abstract Book

S248

ESTRO 2021

oligometastases S. Siva 1,2 , M. Bressel 3 , T. Mai 4 , H. Le 5 , S. Vinod 6 , H. de Silva 7 , S. Macdonald 7 , M. Skala 8 , N. Hardcastle 9 , A. Rezo 10 , D. Pryor 4 , S. Gill 11 , B. Higgs 5 , K. Wagenfuehr 12 , R. Montgomery 12 , R. Awad 8 , B. Chesson 13 , T. Eade 14 , W. Wong 15 , G. Sasso 16 , R. De Abreu Lourenco 17 , T. Kron 9,2 , D. Ball 18,2 , P. Neeson 7,2 1 Peter MacCallum Cancer Centre, Radiation Oncology, Melbourne, Australia; 2 The University of Melbourne, Sir Peter MacCallum Department of Oncology, Melbourne, Australia; 3 Peter MacCallum Cancer Centre, Centre for Biostatistics and Clinical Trials, Melbourne, Australia; 4 Princess Alexandra Hospital, Radiation Oncology Centre, Brisbane, Australia; 5 Royal Adelaide Hospital, Department of Radiation Oncology, Adelaide, Australia; 6 Liverpool Hospital, Cancer Therapy Centre, Sydney, Australia; 7 Peter MacCallum Cancer Centre, Cancer Immunology Program, Melbourne, Australia; 8 Royal Hobart Hospital, Radiation Oncology, Hobart, Australia; 9 Peter MacCallum Cancer Centre, Department of Physical Sciences, Melbourne, Australia; 10 Canberra Hospital, Radiation Oncology, Canberra, Australia; 11 Sir Charles Gairdner Hospital, Department of Radiation Oncology, Perth, Australia; 12 Trans Tasman Radiation Oncology Group (TROG), Cancer Research, Sydney, Australia; 13 Peter MacCallum Cancer Centre, Department of Radiation Therapy, Melbourne, Australia; 14 Royal North Shore Hospital, Northern Sydney Cancer Centre, Sydney, Australia; 15 Prince of Wales Hospital, Department of Radiation Oncology, Sydney, Australia; 16 Auckland City Hospital, Radiation Oncology Department, Auckland, New Zealand; 17 University of Technology Sydney, Centre for Health Economics Research and Evaluation, Sydney, Australia; 18 Peter MacCallum Cancer Centre, Department of Radiation Oncology, Melbourne, Australia Purpose or Objective There is no randomized evidence to guide the optimal approach for SABR in patients with pulmonary oligometastases. We conducted a randomized trial to determine whether single or multi-fraction SABR is optimal. We hypothesized that each arm had acceptable adverse events (AEs), efficacy and quality of life effects, but that single fraction SABR was cost-effective. Materials and Methods The TransTasman Radiation Oncology Group (TROG) 13.01 SAFRON II study was a multicenter unblinded randomized phase II trial across 13 centers in Australia and New Zealand. Enrolment was between 2015 and 2018, with a minimum patient follow-up of 2 years. Participants had 1–3 oligometastases of <5cm diameter to the lung from any non-haematological malignancy, located away from central airways, ECOG 0 - 1, and all primary and extrathoracic disease controlled with local therapy. The interventions were either a Single fraction of 28Gy (SF Arm) or four fractions of 12Gy (MF Arm) to each oligometastasis. The primary outcome was grade ³3 treatment related AEs (CTCAE v4.0) occurring within 1 year of SABR. Secondary outcomes were freedom from local failure (FFLF), overall survival (OS), disease free survival (DFS) and patient reported outcomes (MDASI-LC and EQ-5D VAS). Exploratory baseline and post-treatment peripheral blood was collected in a subset of participants from a single center for translational analysis. Health care resource use, including patient time, and EQ-5D-5L quality of life measures for the assessment of cost-effectiveness were prospectively collected. Results 90 participants were randomized, with n = 87 treated for 133 pulmonary oligometastases. Median follow-up was 36.5 months. Median age was 68 years, 64% were male. Grade ³3 AEs in the MF Arm and SF Arm were 3% [80% CI: 0-10] and 5% [80% CI: 1-13], p = 0.37. There was one grade 5 AE in the MF arm. There were no significant differences between the MF Arm and SF Arm for FFLF (HR 0.5, [95% CI: 0.2-1.3], p = 0.13), OS (HR 1.5 [95% CI: 0.6-3.7], p = 0.44), or DFS (HR 1.0, [95% CI: 0.6-1.6], p = 1.00). The areas under the curve for each of the MDASI-LC subscales and EQ-5D VAS were no different between arms ( p -values 0.12-0.95). Both regimens induced changes in the frequency of immune cell subsets in peripheral blood with potentially altered function (expression of PD-1, TIGIT and CTLA-4 checkpoints) and plasma cytokine levels. Costs for radiotherapy delivery were A$4,943 for the SF Arm and A$6,320 for the MF Arm. For the within trial period, the average cost was estimated to be A$41,700 in the SF Arm and A$39,251 in the MF Arm, with 2.43 quality- adjusted life-years (QALYs) in the SF arm and 2.25 QALYs in the MF arm. The incremental cost-effectiveness ratio for SF SABR compared with MF SABR was A$13,597/QALY gained.