In a phase II study (FASTRACK II) reported in The Lancet Oncology, Shankar Siva, MBBS, PhD, and colleagues found that stereotactic ablative body radiotherapy (SABR) was effective in patients with primary kidney cancer who did not undergo resection.
Shankar Siva, MBBS, PhD
Study Details
Seventy patients were enrolled in the trial from seven Australian centers and one Dutch center between July 2016 and February 2020. Patients had a single lesion and were medically inoperable, at high risk of complications from surgery, or declined surgery. SABR was given at a single fraction of 26 Gy for tumors ≤ 4 cm in maximum diameter or at 42 Gy in three fractions for tumors > 4 cm to 10 cm in maximum diameter.
Patients had a median age of 77 years (interquartile range [IQR] = 70–82 years). The primary endpoint was investigator-assessed local control, defined as no progression of the primary renal cell cancer. If the 1-year local control rate was ≤ 80%, the strategy would be considered unworthy of proceeding to a randomized controlled trial.
Key Findings
Median tumor size was 4.6 cm (IQR = 3.7–5.5 cm). All patients had T1-T2a and N0-N1 disease. A total of 23 patients received a single fraction of SABR, and 47 received three fractions.
Median follow-up was 43 months (IQR = 38–60 months). Local control at 12 months was 100% (P < .0001 vs null hypothesis of ≤ 80%). No local failures were observed during the trial.
Cancer-specific survival was 100%. Freedom from distant failure at both 12 and 36 months was 97% (95% confidence interval [CI] = 89%–99%). Overall survival was 99% (95% CI = 90%–100%) at 12 months and 82% (95% CI = 70%–89%) at 36 months.
Baseline mean estimated glomerular filtration rate was 61.1 mL/min per 1.73 m², changed by –10.8 mL/min per 1.73 m² at 12 months and by –14.6 mL/min per 1.73 m² at 24 months, and plateaued thereafter.
Grade 3 treatment-related adverse events occurred in seven patients (10%), including nausea and vomiting (4%); abdominal, flank, or tumor pain (6%); colonic obstruction (3%); and diarrhea (1%). No grade 4 or 5 events were observed.
The investigators concluded, “To our knowledge, this is the first multicenter prospective clinical trial of nonsurgical definitive therapy in patients with primary renal cell cancer. In a cohort with predominantly T1b or larger disease, SABR was an effective treatment strategy with no observed local failures or cancer-related deaths. We observed an acceptable side effect profile and renal function after SABR. These outcomes support the design of a future randomized trial of SABR vs surgery for primary renal cell cancer.”
Dr. Siva, of the Department of Radiation Oncology, Peter MacCallum Cancer Centre, Melbourne, is the corresponding author for The Lancet Oncology article.
Disclosure: The study was funded by the Cancer Australia Priority–driven Collaborative Cancer Research Scheme. For full disclosures of the study authors, visit thelancet.com.
