SABR Provides Novel Alternative to Surgical Resection for Primary RCC

Surgical resection is viewed as a benchmark treatment for patients with primary renal cell cancer (RCC). However, for those who may be ineligible or unwilling to undergo surgery, novel stereotactic ablative body radiotherapy (SABR) is a noninvasive alternative.

The nonrandomized, phase 2 FASTRACK II trial led by Shankar Siva, MBBS, PhD, was the first multicenter, prospective, clinical trial of its kind to examine nonsurgical definitive therapy in patients with primary RCC. The trial’s newly released results demonstrate that SABR may be an effective treatment strategy.

Eligible patients were 18 years of age or older, had a biopsy-confirmed diagnosis of primary RCC with only a single lesion, were medically inoperable, were at high risk of complications from surgery or declined surgery, and had an Eastern Cooperative Oncology Group performance status of 0-2. A multidisciplinary decision that active treatment was warranted was required.

A total of 70 patients with a median age of 77 years (range, 70-82 years) were enrolled in the trial and began treatment between July 2016 and February 2020. Patients with tumors 4 cm or smaller were administered SABR of 26 Gy for 1 fraction, and those with tumors larger than 4 cm and up to 10 cm in maximum diameter were administered 42 Gy in 3 fractions. The primary end point was local control, defined as no disease progression as evaluated by the investigator per Response Evaluation Criteria in Solid Tumors, version 1.1.

The median tumor size was 4.6 cm (range, 3.7-5.5 cm), and all patients enrolled had T1-T2a and N0-N1 disease. Single-fraction SABR was administered to 23 patients, while the 3-fraction dosing was administered to 47. The median follow-up was 43 months (range, 38-60 months), and the local control at 12 months after treatment initiation was 100% (P<.0001).

Grade 3 treatment-related adverse events (AEs)—nausea and vomiting; abdominal, flank, or tumor pain; colonic obstruction; and diarrhea—occurred in 7 (10%) patients. No grade 4 AEs were observed, and no treatment-related or cancer-related deaths occurred.

SABR was shown to be an effective treatment strategy for patients with primary RCC, with no observed local failures. An acceptable side-effect profile and renal function were consistent in patients after treatment, supporting further research into comparing SABR against surgery for primary RCC.