Stereotactic Ablative Body Radiotherapy Achieves 100% Local Control in Primary Kidney Cancer: FASTRACK II Final Results
Key Insights
The FASTRACK II phase 2 trial demonstrated 100% freedom from local progression with stereotactic ablative body radiotherapy (search) (SABR) in patients with primary renal cell carcinoma (search) over a median follow-up of 62 months.
The non-randomised study enrolled 71 patients across Australia and the Netherlands who were medically inoperable, at high surgical risk, or declined surgery, with tumours up to 10 cm.
No cancer-related deaths or grade 4 toxicities were observed; grade 3 adverse events occurred in 10% of patients within nine months of treatment.
Stereotactic ablative body radiotherapy (search) (SABR) delivered durable long-term local control in patients with primary renal cell carcinoma (search), according to final results from the FASTRACK II phase 2 trial conducted across Australia and the Netherlands. The findings, presented at ESTRO26 and simultaneously published in The Lancet Oncology, showed 100% freedom from local progression with no local recurrences across follow-up extending to 84 months.
The FASTRACK II study was a non-randomised phase 2 trial led by the TransTasman Radiation Oncology Group (search) and the Australian and New Zealand Urogenital and Prostate Cancer Trials Group (search). It evaluated SABR as a non-invasive alternative for patients with primary renal cell carcinoma (search) who were medically inoperable, at high surgical risk, or who declined surgery.
Trial Design and Dosing
A total of 71 adult patients were enrolled across eight hospitals, with one patient withdrawing before treatment. The median follow-up period was 62 months, and the median age was 77 years. Most participants had early-stage disease, with the majority classified as T1b or higher, and the cohort included patients with tumours up to 10 cm in size.
Patients received either a single 26 Gy fraction for tumours measuring 4 cm or less, or 42 Gy delivered in three fractions for tumours larger than 4 cm.
Efficacy Outcomes
The primary endpoint was freedom from local progression, assessed using Response Evaluation Criteria in Solid Tumours (RECIST) criteria. Across follow-up periods extending to 84 months, SABR achieved 100% local control, with no reported local recurrences in the treated cohort.
Investigators reported no cancer-related deaths during follow-up, supporting sustained disease control in a population largely unable to undergo surgical intervention.
Safety Profile
Safety analysis showed that 10% of patients experienced grade 3 adverse events within nine months of treatment that were considered possibly, probably, or definitely related to SABR. Reported events included nausea and vomiting, abdominal or tumour-related pain, colonic obstruction, and diarrhoea.
Importantly, no new long-term safety signals, grade 4 toxicities, or treatment-related deaths were observed during extended follow-up.
Clinical Implications
These findings suggest that SABR may offer a durable, non-invasive treatment option for selected patients with renal cell carcinoma (search) who are unsuitable for surgery, with sustained local control and an acceptable safety profile over long-term follow-up. The results position SABR as a meaningful alternative in the management of primary kidney cancer, particularly for elderly patients and those with significant surgical risk factors.