(UroToday.com) The 2023 American Society for Radiation Oncology (ASTRO) 65th Annual Meeting held in San Diego, CA between October 1st and 4th, 2023 was host to a session on radiotherapy for kidney cancer and the post-prostatectomy setting. Dr. Vivian Tan presented the results of an analysis of the International Radiosurgery Oncology Consortium of the Kidney (IROCK) evaluating the 5-year renal function outcomes following stereotactic ablative radiotherapy (SABR) for primary renal cell carcinoma.
Dr. Tan began by noting that the incidence of renal cell carcinoma continues to rise with the increased utilization of cross-sectional imaging in practice. This increase has been most notable in patients older than 70 years of age, many of whom are frail and have numerous medical comorbidities that may preclude surgical or percutaneous interventions.
Currently, available management options for RCC patients have several important limitations. Nephrectomy requires general anesthesia and can be morbid in these elderly, frail patients. Conversely, thermal ablative procedures, such as radiofrequency ablation and cryoablation, can be technically challenging for larger, perihilar tumors with worsening efficacy outcomes with increasing sizes. SABR, which entails image-guided, precision targeted delivery of high radiotherapy doses in limited fractions, may be an attractive treatment option in this setting, given that this treatment modality avoids general anesthesia, is feasible for large, perihilar tumors, and is non-invasive.
It is currently unknown if SABR is safe for patients with solitary kidneys. The objective of this study is to compare the long-term renal function of SABR in patients with solitary versus bilateral kidneys. To this end, the authors utilized individual level data from the IROCK consortium of 12 centers. Patients were included if they had biopsy-proven RCC histology, serial mass enlargement, and follow up of at least 2 years duration.
This analysis included 190 patients, followed for a median of 5 years (IQR: 3.4 to 6.8 years).
Compared to those with bilateral kidneys in situ, those with solitary kidneys were younger (69 versus 76 years), had better performance status, and had a longer median duration from diagnosis to SABR (44.8 versus 3.3 months). They were also more likely to have clear cell histology (98% versus 80%) and slightly smaller tumors (3.7 versus 4 cm). They also received a lower median total dose (25 versus 35 Gy), a lower number of fractions (1 versus 3 fractions), with an equal biologic equivalent dose 10 (BED10) of 87.5 Gy.
The mean baseline eGFR was similar in both groups, at 61.1 mL/min and 58 mL/min in the solitary and bilateral kidney groups, respectively (p=0.32). While the rate of eGFR decline was most prominent in the first 2 years, there were no significant differences in the mean eGFR change overall and at 5 years (solitary: -14.5 mL/min; bilateral: -13.3 mL/min).
When evaluating the outcome of eGFR decline by ≥15 mL/min on an annual basis, there were no significant differences between the two cohorts. Conversely, there were also no differences in the proportions of those with an eGFR increase by ≥15 mL/min between the two cohorts.
The proportion of patients progressing to ESRD (solitary: 7.1%; bilateral: 6.7%) and dialysis (solitary: 3.6%; bilateral: 3.7%) were similar for both groups. Multivariable analysis evaluating predictors of eGFR decline by ≥15 mL/min at 1-year demonstrated the following significant variables:
- Tumor size (OR: 1.57, 95% CI: 1.14 – 2.15)
- Baseline eGFR (OR: 1.30, 95% CI: 1.02 – 1.66)
Solitary versus bilateral kidney status was not a significant predictor of eGFR decline by ≥15 mL/min at 1 year (OR: 1.22, 95% CI: 0.45 – 3.34, p=0.69).
Dr. Tan concluded her presentation with the following take home messages:
- SABR appears safe and effective for patients with a solitary kidney
- Long-term renal function decline is moderate, with a low rate of dialysis
Presented by: Vivian Tan, MD, Resident Physician, Department of Radiation Oncology, Western University, London, ON
Written By: Rashid K. Sayyid, MD, MSc – Society of Urologic Oncology (SUO) Clinical Fellow at The University of Toronto, @rksayyid on Twitter during the 2023 American Society for Therapeutic Radiation Oncology (ASTRO) 65th Annual Meeting held in San Diego, CA between October 1st and 4th, 2023