Stereotactic ablative radiotherapy (SABR) has emerged as a new treatment option for patients with oligometastatic disease. SABR delivers precise, high-dose, hypofractionated radiotherapy, and achieves excellent rates of local control for primary tumors or metastases. A recent randomized phase II trial evaluated SABR in a group of patients with a small burden of oligometastatic disease (mostly with 1–3 metastatic lesions), and found that SABR was associated with benefits in progression-free survival and overall survival. The goal of this phase III trial is to assess the impact of SABR in patients with 4–10 metastatic cancer lesions. One hundred and fifty-nine patients will be randomized in a 1:2 ratio between the control arm (consisting of standard of care palliative-intent treatments), and the SABR arm (consisting of standard of care treatment + SABR to all sites of known disease). Randomization will be stratified by two factors: histology (Group 1: prostate, breast, or renal; Group 2: all others), and type of pre-specified systemic therapy (Group 1: immunotherapy/targeted; Group 2: cytotoxic; Group 3: observation). SABR is to be completed within 2 weeks, allowing for rapid initiation of systemic therapy. Recommended SABR doses are 20 Gy in 1 fraction, 30 Gy in 3 fractions, or 35 Gy in 5 fractions, chosen to minimize risks of toxicity. The primary endpoint is overall survival, and secondary endpoints include progression-free survival, time to development of new metastatic lesions, quality of life, and toxicity. Translational endpoints include assessment of circulating tumor cells, cell-free DNA, and tumor tissue as prognostic and predictive markers, including assessment of immunological predictors of response and long-term survival. This study will provide an assessment of the impact of SABR on clinical outcomes and quality of life, to determine if long-term survival can be achieved for selected patients with 4–10 oligometastatic lesions. Clinicaltrials.gov identifier: NCT03721341 . Date of registration: October 26, 2018.

Stereotactic ablative radiotherapy (SABR) has emerged as a new treatment option for patients with oligometastatic disease. SABR delivers precise, high-dose, hypofractionated radiotherapy, and achieves excellent rates of local control. Survival outcomes for patients with oligometastatic disease treated with SABR appear promising, but conclusions are limited by patient selection, and the lack of adequate controls in most studies. The goal of this multicenter randomized phase II trial is to assess the impact of a comprehensive oligometastatic SABR treatment program on overall survival and quality of life in patients with up to 5 metastatic cancer lesions, compared to patients who receive standard of care treatment alone.

Although radiotherapy is a key component of curative-intent treatment for locally advanced, unresectable non-small cell lung cancer (NSCLC), it can be associated with substantial pulmonary toxicity in some patients. Current radiotherapy planning techniques aim to minimize the radiation dose to the lungs, without accounting for regional variations in lung function. Many patients, particularly smokers, can have substantial regional differences in pulmonary ventilation patterns, and it has been hypothesized that preferential avoidance of functional lung during radiotherapy may reduce toxicity. Although several investigators have shown that functional lung can be identified using advanced imaging techniques and/or demonstrated the feasibility and theoretical advantages of avoiding functional lung during radiotherapy, to our knowledge this premise has never been tested via a prospective randomized clinical trial.

Purpose: The oligometastatic paradigm hypothesizes that patients with a limited number of metastases may achieve long-term disease control, or even cure, if all sites of disease can be ablated. However, long-term randomized data testing this paradigm are lacking. Methods: We enrolled patients with a controlled primary malignancy and 1-5 metastatic lesions, with all metastases amenable to stereotactic ablative radiotherapy (SABR). We stratified by the number of metastases (1-3 vs. 4-5) and randomized in a 1:2 ratio between palliative standard of care (SOC) treatments (Arm 1) vs. SOC plus SABR (Arm 2). We employed a randomized phase II screening design with a primary endpoint of overall survival (OS), using an alpha of 0.20 (wherein a p-value <0.20 indicates a positive trial). Secondary endpoints included progression-free survival (PFS), toxicity, and quality of life (QOL). Herein we present long-term outcomes from the trial. Results: Between 2012 and 2016, 99 patients were randomized (33 in Arm 1, 66 in Arm 2) at 10 centres internationally. Median age was 68 (range 43-89) and the majority (n=59; 60%) were male. The most common primary tumor types were breast (n=18), lung (n=18), colorectal (n=18), and prostate (n=16). Median follow-up was 51 months. Five-year OS was 17.7% in Arm 1 (95% confidence interval [CI]: 6-34%) vs. 42.3% in Arm 2 (95% CI: 28-56%; stratified log-rank p=0.006). Five-year PFS was ‘not reached’ in Arm 1 (3.2% [95% CI: 0-14%] at 4-years with last patient censored) and was 17.3% (95% CI: 8-30%) in Arm 2 (p=0.001). There were no new grade 2-5 adverse events and no differences in QOL between arms. Conclusions: With extended follow-up, the impact of SABR on OS was larger in magnitude than in the initial analysis, and durable over time. There were no new safety signals, and SABR had no detrimental impact on QOL. ( NCT01446744 ) Funding: Ontario Institute for Cancer Research and London Regional Cancer Program Catalyst Grant