The International Radiosurgery Oncology Consortium for Kidney (IROCK, Siva et al, IJROBP, 2020) reported the largest cohort of larger (T1b, > 4 cm) RCC who were deemed to be inoperable and treated with definitive SBRT. They pooled data from 9 institutions, representing ~100 patients with a median follow-up of 2.7 years, and a median age of 76 years.
Definitive SBRT provided excellent disease control, with 4-year local control and distant control rates of 97.1% and 88.9%, respectively. Cancer-specific survival (CSS), overall survival OS), and progression-free survival (PFS) were 91.4%, 69.2%, 64.9% at 4 years, respectively.
~50% of patients had pre-existing chronic kidney disease. In the cohort without pre-existing renal dysfunction, about 1/3 developed CKD after SBRT about 2 years after treatment, with an average reduction in GFR of 7.9 mL/min. Only 3.2% of patients developed progression of CKD requiring dialysis despite that 29.5% of patients presented with a solitary kidney. There were no grade 3 or higher complications.
Clinical Pearl: For larger, inoperable RCC (> 4 cm), definitive SBRT provides excellent long-term local control and disease control with low rates of reported treatment associated complications.
