SABR metrics.

Top Line: Can safe and effective SABR for oligometastatic cancer be translated to a regional cancer network?

The Study: The SABR-5 trial, presented at ASTRO 2021, was a single-arm, multicenter trial conducted throughout British Columbia to assess the safety and efficacy of SABR for oligometastatic disease in a regional health system. This manuscript reports survival and control outcomes. The population (n=381) was heterogeneous, but patients could have no more than 5 metastatic lesions (including intracranial lesions) and those had to be eligible for SABR. This included patients with true oligometastatic disease as well as those with “induced” oligometastatic disease (13%) or oligoprogressive disease (16%). The majority (68%) had just a single metastasis. Primary disease had to be either controlled or treated radically along with oligometastatic disease. The most common histologies were prostate (32%), colorectal (17%), and breast (11%). The most common target sites were lung (35%), non-spine bone (25%), and spine (15%). Treatment planning prioritized organ-at-risk constraints over target coverage. Median progression free survival was 15 months, and the rates of PFS at 1 and 2 years were 56% and 31%, respectively. PFS was significantly longer among those with true oligometastatic (18 v 11 months). Overall survival at 3 years was 71%. SABR was highly effective in local control with a 3-year lesion control rate of 87%. Most progression events involved only new metastases without local recurrence (83%). Tumor size and histology were the strongest predictors of local recurrence with colorectal cancer lesions having a significantly higher risk of recurrence.

TBL: SABR-5 provides a safe and effective framework for treating oligometastatic cancer. Local lesion control was extremely high with most patients failing at new sites. | Baker, Int J Radiat Oncol Biol Phys 2022