Genitourinary Cancer

SS 30 - GU 4 - SBRT for Prostate and Renal Cancers

222 - Renal SABR in Patients With a Solitary Kidney: An Individual-Patient Pooled Analysis From the International Radiosurgery Oncology Consortium for Kidney (IROCK)

Tuesday, October 23
5:55 PM - 6:05 PM
Location: Room 214 C/D

Renal SABR in Patients With a Solitary Kidney: An Individual-Patient Pooled Analysis From the International Radiosurgery Oncology Consortium for Kidney (IROCK)
R. J. M. Correa1, S. Siva2, M. Staehler3, A. Warner1, S. Gandhidasan4, L. Ponsky5, R. J. Ellis III6, I. D. Kaplan7, A. Mahadevan7, W. Chu8, A. Swaminath9, H. Onishi10, B. S. Teh11, S. S. Lo12, A. Muacevic13, and A. V. Louie1; 1London Regional Cancer Program, London, ON, Canada, 2Peter MacCallum Cancer Center, Melbourne, Australia, 3University of Munich, Munich, Germany, 4Peter MacCallum Cancer Centre, Melbourne, Australia, 5Urology, University Hospitals Cleveland Medical Center, Cleveland, OH, 6Radiation Oncology, University Hospitals Seidman Cancer Center, Cleveland, OH, 7Beth Israel Deaconess Medical Center, Boston, MA, 8Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, ON, Canada, 9Juravinski Cancer Centre, Hamilton, ON, Canada, 10University of Yamanashi, Chuo, Japan, 11Department of Radiation Oncology, Houston Methodist Hospital, Houston, TX, 12University of Washington, Department of Radiation Oncology, Seattle, WA, 13University of Munich Hospitals, Munich, Germany

Purpose/Objective(s): SABR is an emerging ablative modality for primary renal cell carcinoma (RCC). Taking a multi-institutional and multi-national approach, we sought to evaluate oncologic and renal function outcomes in patients with RCC in solitary kidneys versus bilateral kidneys.

Materials/Methods: Individual patient data from 9 institutions across Germany, Australia, USA, Canada and Japan within the IROCK group were pooled retrospectively. Toxicities were recorded using CTCAE v4.03. Demographics and treatment outcomes were compared between those patients with solitary vs. bilateral functional kidneys using chi-square test, fisher’s exact test, two-sample T-test or Wilcoxon rank sum test as appropriate. K-M estimates and Cox proportional hazards regression were generated for survival outcomes.

Results: 81 patients (of 223 total) harboring a solitary kidney underwent renal SABR. Mean age in this cohort was 62.5 years, 69% of patients were male, and 97.5% had good performance status (ECOG 0-1). Twelve patients (14.8%) had metastatic disease. Pathological confirmation was obtained in 91.4% (all clear cell RCC) with a further 8.6% demonstrating tumor growth on serial imaging. Median [IQR] diameter of solitary kidney tumors was 3.7cm [2.5-4.3], which was smaller (p<0.001) than those in patients with bilateral kidneys (4.3cm [3.0-5.5]). The median (range) total dose and number of fractions were 25Gy (14-70) and 1 (1-10), respectively. While both total dose and number of fractions were significantly lower in the solitary cohort (p≤0.001), median (range) BED10 was similar between cohorts: 87.5Gy (33.6-125) in the solitary and 87.5Gy (37.5-125) in the bilateral cohort (p=0.103). Solitary kidney patients had a higher mean ± SD eGFR at baseline (64.6±21.7 mL/min) than those with bilateral kidneys (57.2±21.6 mL/min; p=0.016). Post-SABR decline in eGFR was similar for solitary and bilateral cohorts with mean (±SD) decreases of -5.8 (±10.8) and -5.3 (±14.3) mL/min, respectively (p=0.984). No patients in the solitary cohort required dialysis vs. 6 (4.2%) in the bilateral cohort. With median follow-up of 2.57 years, local control (LC), progression free survival (PFS), cancer-specific survival (CSS), and overall survival (OS) at 2 years were 98.0%, 77.5%, 98.2% and 81.5%, respectively. No difference in local failure rate for solitary (n=1) versus bilateral (n=2) cohorts was observed (p=1.00). On univariable analysis, moderate chronic kidney disease (eGFR ≤ 60 mL/min) was associated with poorer PFS (HR 2.66, p=0.043) in the solitary cohort.

Conclusion: Renal SABR appears to be a safe and well-tolerated option for RCC tumors in patients with solitary kidneys and yields comparable local control, survival, and renal function outcomes to patients with bilateral kidneys. Pre-existing moderate chronic kidney disease in patients with a solitary kidney may be predictive of poorer oncologic outcomes in this group, thus careful patient selection will be essential to optimize outcomes in this population.

Author Disclosure: R.J. Correa: None. S. Siva: Research Grant; Varian. A. Warner: None. S. Gandhidasan: None. R.J. Ellis: Partner; ADvanced Clinical Solutions Inc. Patent/License Fees/Copyright; ADvanced Clinical Solutions. A. Mahadevan: Employee; Harvard MEdical Faculty Physicians. Salary; Harvard Medical Faculty Physicians. Royalty; UptoDate. Chairman of the Board of Directors; The Radiosurgery Sociey. W. Chu: None. A. Swaminath: None. B.S. Teh: None. S.S. Lo: Chair; American College of Radiology. Radiation Oncology Track Chair; Radiological Society of North America (RSNA). President-Elect; American College of Radiology. A.V. Louie: None.

Rohann Correa, MD, PhD

London Regional Cancer Program

Disclosure:
No relationships to disclose.

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