Stereotactic Ablative Body Radiotherapy for Inoperable Primary Kidney Cancer: A Prospective Clinical Trial

To assess the feasibility and safety of stereotactic ablative body radiotherapy (SABR) for RCC in patients unsuitable for surgery. Secondary objectives were to assess oncologic and functional outcomes.

This was a prospective interventional clinical trial with institutional ethics board approval. Inoperable patients were enrolled after multidisciplinary consensus for intervention and informed consent. Tumor response was defined using RECIST 1.1 criteria. Toxicities were recorded using CTCAE v4.0. Time-to-event outcomes were described using Kaplan-Meier method and associations of baseline variables with tumor shrinkage was assessed using linear regression. Patients received either single fraction of 26Gy or three fractions of 14Gy dependent on tumour size.

Of 37 patients (median age of 78 years), 62% had T1b, 35% had T1a and 3% had T2a disease. One patient presented with bilateral primaries. Histology was confirmed in 92%. In total 33 patients and 34 kidneys received all prescribed SABR fractions (89% feasibility). The median follow-up was 24 months. Treatment related grade 1-2 toxicities occurred in n=26 (78%), grade 3 toxicity in n=1 (3%). No grade 4-5 toxicities were recorded and n=6 (18%) reported no toxicity. Freedom from local progression, distant progression and overall survival at 2 years were 100%, 89% and 92%, respectively. The mean baseline GFR was 55 mL/min, which decreased to 44 mL/min at 1 and 2 years (p < 0.001). Neutrophil to lymphocyte (N/L) ratio was correlated to % change in tumor size at 1-year, r(2) =0.45, p<0.001.

SABR for primary RCC is feasible and well tolerated. We observed encouraging cancer control, functional preservation and early survival outcomes in an inoperable cohort. Baseline N/L ratio may be predictive of immune-mediated response and warrants further investigation. Limitations include lack of long-term oncologic and functional outcomes. This article is protected by copyright. All rights reserved.

BJU international. 2017 Feb 10 [Epub ahead of print]

Shankar Siva, Daniel Pham, Tomas Kron, Mathias Bressel, Jacqueline Lam, Tan Teng Han, Brent Chesson, Mark Shaw, Sarat Chander, Suki Gill, Nicholas R Brook, Nathan Lawrentschuck, Declan G Murphy, Farshad Foroudi

Peter MacCallum Cancer Centre, Melbourne, Australia, 3000., Royal Adelaide Hospital, Adelaide, Australia, 5000.