As reported in The Lancet Oncology by Siva et al, 5-year findings in a pooled analysis of the FASTRACK and FASTRACK II trials support evidence of maintained disease control with ultra-hypofractionated stereotactic ablative body radiotherapy (SABR) in patients with primary renal cell carcinoma considered inoperable or posing high surgical risk.
Study Details
The study used pooled data from 108 patients in FASTRACK (enrollment between June 2012 and October 2014), a single-institution phase I trial conducted at the Peter MacCallum Cancer Centre (Melbourne, Australia), and FASTRACK II (enrollment between July 2016 and February 2020), an international, nonrandomized, phase II trial conducted in seven academic hospitals in Australia and one in the Netherlands. Treatment protocol, inclusion and exclusion criteria, and dose constraints were the same in both trials. Patients (median age = 76.9 years) had tumors of 10 cm or less in maximal dimension and N0-N1 disease. Tumors 4 cm or smaller in FASTRACK II and smaller than 5 cm in FASTRACK received a single fraction of 26 Gy, with larger tumors receiving 42 Gy in three fractions 48 hours apart. Local control (freedom from local progression) was the primary outcome measure.
Key Findings
Median follow-up was 5.0 years (interquartile range = 2.3–6.0 years).
Local control was 100% at 1 year, 98% (95% confidence interval [CI] = 89%–100%) at 3 years, and 98% (95% CI = 89%–100%) at 5 years. Local progression was observed in only one patient, who experienced both local and distant progression at 28 months.
Grade 3 adverse events included abdominal or flank pain (4%), nausea or vomiting (2%), colonic obstruction (2%), fatigue (1%), and colitis or diarrhea (1%); all occurred within 2 years of SABR delivery. No grade 4 adverse events or treatment-related deaths were reported.
The investigators concluded: “This pooled analysis from two clinical trials of SABR in patients with larger primary kidney tumours unsuitable for surgery supports evidence of long-term local control and low rate of severe adverse events. These results support further investigation through a randomised trial comparing SABR with surgery in select operable patients.”
Shankar Siva, MBBS, PhD, of the Department of Radiation Oncology, Peter MacCallum Cancer Centre, Melbourne, Australia, is the corresponding author for The Lancet Oncology article.
DISCLOSURE: The investigators reported that there was no external funding for the study. For full disclosures of the study authors, visit thelancet.com.
