Population-based phase II trial of stereotactic ablative radiotherapy (SABR) for up to 5 oligometastases: SABR-5

Abstract

Background: Oligometastases refer to a state of disease where cancer has spread beyond the primary site, but is not yet widely metastatic, often defined as 1-3 or 1-5 metastases in number. Stereotactic ablative radiotherapy (SABR) is an emerging radiotherapy technique to treat oligometastases that require further prospective population-based toxicity estimates.

Methods: This is a non-randomized phase II trial where all participants will receive experimental SABR treatment to all sites of newly diagnosed or progressing oligometastatic disease. We will accrue 200 patients to assess toxicity associated with this experimental treatment. The study was powered to give a 95% confidence on the risk of late grade 4 toxicity, anticipating a < 5% rate of grade 4 toxicity.

Discussion: SABR treatment of oligometastases is occurring off-trial at a high rate, without sufficient evidence of its efficacy or toxicity. This trial will provide necessary toxicity data in a population-based cohort, using standardized doses and organ at risk constraints, while we await data on efficacy from randomized phase III trials.

Trial registration: Registered through clinicaltrials.gov NCT02933242 on October 14, 2016 prospectively before patient accrual.

Keywords: Oligometastases; Radiotherapy; Stereotactic ablative radiotherapy.