3290 - Practice Patterns of Primary Stereotactic Radiotherapy for Renal Cell Carcinoma in the United States

Y. S. Soni¹, S. Woldu², X. Meng², A. Garant¹, N. B. Desai¹, R. Hannan¹, and D. X. Yang¹; ¹Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX, ²Department of Urology, University of Texas Southwestern Medical Center, Dallas, TX

Purpose/Objective(s): Most primary renal cell carcinomas (RCC) are managed locally with surgery, ablative techniques, or active surveillance. However, there is now prospective evidence and long-term registry outcomes for the management of RCC with stereotactic ablative radiotherapy (SAbR). In this study, we aim to investigate contemporary changes in the use of SAbR for primary RCC in the United States. Materials/

Methods: We queried the National Cancer Database (NCDB) from 2004-2020 for histologically proven RCC. We identified patients age >=18 with known histologic diagnosis and staging. Primary RCC SAbR was defined as radiation delivered in 5 or less fractions to the kidney with a dose per fraction of 6 Gy or higher. Patients with missing or unknown radiation records were excluded.
Results: Of 27,818 patients with primary RCC, 257 patients underwent SAbR to the kidney. The median age at diagnosis was 74 for those who underwent SAbR and 64 for the entire cohort (p<0.001). For those pts who underwent SAbR, most were identified to have clear cell histology 221/257 (86%). Mean tumor size was 2.97 cm in SAbR cohort and 6.25 cm for the entire cohort (p<0.01). 164 (63.81%) patients were stage I, 20 (7.78%) patients were stage II, 33 (12.84%) patients were stage III, and 40 (15.56%) patients were stage IV. The median Charlson-Deyo score was 0 (range 0-3) for the SAbR cohort. The three most common regimens were 40 Gy in 5 fractions (24.12%), 50 Gy in 5 fractions (16.34%) and 42 Gy in 3 fractions (6.61%). There was a clear increase in SAbR use from 2017-2020, with the proportion of patients who received primary RCC SAbR rising from 0.15% to 3.76% to 4.73%, and 4.93% respectively over those 4 years (p<0.01). Limitations of our study include likely underreporting due to excluding patients without a histologic diagnosis and known radiation records.
Conclusion: There has been a significant and progressive increase in use of SAbR for primary RCC patients starting from 2017 in the United States. This coincides with the appearance of published evidence on primary RCC management with SAbR which is expected to continue to increase as SAbR becomes incorporated into the multi-disciplinary management of RCC.

Abstract 3290 – Table 1

Percentage Increase in Primary Renal SAbR Year to Year by Stage
	2017 (%)	2018 (%)	2019 (%)	2020 (%)
Stage I	0.10	2.28	3.10	2.85
Stage II	0.00	0.41	0.25	0.88
Stage III	0.00	0.71	0.44	0.49
Stage IV	0.05	0.36	0.94	0.71