Stereotactic Ablative Body Radiotherapy Improved Survival, Maintained Safety for Oligometastatic Cancers

The use of stereotactic ablative body radiotherapy (SABR) among patients with extracranial oligometastatic cancer was associated with higher overall survival (OS) and low toxicity rates, signaling the potential success for this treatment option moving forward, according to data published in The Lancet Oncology.

The data are supported by existing literature from a randomized phase 2 trial, providing even more high-level, real-world evidence in support of SABR for patients in this disease cohort. A randomized, phase 3 trial is currently underway to evaluate this treatment option further.

“The results show that patients with metachronous extracranial oligometastases treated with SABR in a real-world setting achieve high rates of 1-year and 2-year OS with low rates of severe (grade 3-4) toxicity,” wrote the investigators. “Our study provides real-world evidence characterising the use of SABR in this patient cohort, and also compliments the findings of SABR-COMET [NCT01446744] with regard to OS, but suggests a lower toxicity.”

Median OS rate was recorded at 92.3% (95% CI, 90.5%-93.9%) at 1 year and 79.2% (95% CI, 76.0%-82.1%) at 2 years for the patient population. The OS rate varied according to primary tumor sites, with patients with melanoma at 2 years having an OS rate of 60.5% (95% CI, 38.0%-77.0%) compared with 94.6% (95% CI, 90.4%-97.0%) for patients with prostate cancer.

The most common adverse events were fatigue (56.4%) and cough (16.0%), with fatigue also seen as the most common grade 3 or greater adverse event (2.0%). The most common grade 4 adverse event was increased liver enzymes (1%), while no deaths were recorded due to adverse events.

The median age of the patient population (n = 1422) was 69 years (interquartile range, 62-76). Of that population, 947 patients (66.6%) were men. The median follow-up time was 13 months (range, 6-23) for the patient population.

“This study strengthens the available evidence in the literature supporting the use of SABR in appropriately selected patients with metachronous extracranial oligometastases, and resulted in routine commissioning of SABR for the treatment of patients with oligometastatic disease by NHS England in 2020,” wrote the investigators.

One of the main strengths of this study included the large cohort of patients with metachronous extracranial oligometastatic cancer analyzed in the data. More, each institution was required to participate in a training for SABR, ensuring consistency and safety across various sites.

As for a limitation of the trial, the research team suggests that the low recruitment in the first year of the trial, resulting in a short follow-up period, was a potential limitation. As a result, median OS was not met, resulting in an inability to evaluate the long-term safety and efficacy of SABR.

“Future national data collections such as this should take advantage of research opportunities related to a national cohort (often not possible for RCTs),” wrote the investigators. “Information governance requirements exist, but long-term outcomes could be assessed via data linkage.”

Reference:

Chalkidou A, Macmillan T, Grzeda MT, et al. Stereotactic ablative body radiotherapy in patients with oligometastatic cancers: a prospective, registry-based, single-arm, observational, evaluation study. Lancet Oncol. 2021;22(1):98-106. doi: 10.1016/S1470-2045(20)30537-4