Long-term Results of the SABR-COMET Randomized Trial – The Benefits Still Hold

Presenting author:
David A. Palma, MD, PhD

By Simon S. Lo, MB, ChB, FASTRO

After the presentation and publication of the preliminary results of the Stereotactic Ablative Radiotherapy (SABR)-COMET randomized trial (Arm 1: Standard of Care versus Arm 2: SABR to 1-5 oligometastases) at the ASTRO 2018 Annual Meeting Plenary session and Lancet in 2019, respectively, Palma et al. presented the long term results of this trial. Ninety-nine patients were randomized in a 1:2 ratio (33 in Arm 1 and 66 in Arm 2). In this follow-up report, Stereotactic Ablative Radiotherapy for the Comprehensive Treatment of Oligometastatic Cancers: Long-term Results of the SABR-COMET Randomized Trial, the median follow-up was 51 months. The most common histologies were breast, lung, colorectal and prostate.

With longer follow-up, the magnitude of benefit of SABR was more than in the original report and durable beyond five years. Similar to the preliminary report, the median overall survival (OS) for Arm 2 was longer than that of Arm 1 (50 months versus 28 months) and the p-value was 0.006. The five-year OS rates were 17.7% and 42.3% for Arm 1 versus Arm 2, respectively. The median progression-free survival (PFS) for Arm 1 and Arm 2 were 5.4 and 11.6 months, respectively (p = 0.001). The corresponding five-year progression-free survival (PFS) rates were 0% and 17.3%. There was no difference in the time to new metastasis development between the two arms, and the quality of life (QOL) was similar. The grade 2-5 adverse events were 9% versus 29% for Arm 1 versus Arm 2 (p = 0.03) with no change over time. Long-term lesional control was better in Arm 2 (63% versus 46%, p = 0.039). The use of follow-up systemic therapy was similar. One and nine patients in Arms 1 and 2 received salvage SABR, respectively.

The authors concluded that the benefits of SABR were larger compared to standard of care with extended follow-up, there was no new safety signal and SABR did not impair QOL. The relatively lower magnitude of PFS benefit of six months from SABR and the significant rates of salvage SABR might indicate that undetected micrometastatic disease at presentation could be salvaged with SABR at progression.

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Stereotactic Ablative Radiotherapy for the Comprehensive Treatment of Oligometastatic Cancers: Long-term Results of the SABR-COMET Randomized Trial was released onDemand on Tuesday, October 27 in the Science Center, as part of Scientific Session (SS) 31.

Published on: October 28, 2020


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