Stereotactic Body Radiotherapy for Renal Cell Carcinoma: Oncological and Renal Function Outcomes

Area of Science:

• Oncology
• Radiation Oncology
• Nephrology

Background:

• Medically inoperable patients with localized renal cell carcinoma (RCC) often have limited treatment options.
• Stereotactic body radiotherapy (SBRT) has emerged as a potential curative-intent treatment for such cases.
• Evaluating both oncological control and renal function is crucial for assessing SBRT's efficacy and safety in RCC.

Purpose of the Study:

• To assess the oncological outcomes, specifically local control and distant metastasis, of SBRT for localized renal cell carcinoma in medically inoperable patients.
• To evaluate the impact of SBRT on global and differential renal function, including estimated glomerular filtration rate (eGFR) and ipsilateral/contralateral kidney function.
• To identify clinical and dosimetric factors associated with oncological and renal function outcomes following SBRT for RCC.

Main Methods:

• A cohort of medically inoperable patients with localized renal cell carcinoma treated with curative-intent SBRT (30-45 Gy in 5 fractions or 42 Gy in 3 fractions) was analyzed.
• Oncological data included local control (RECIST v1.1) and distant metastasis. Renal function was assessed by eGFR and proportional ipsilateral/contralateral renal function via renal scans.
• Univariate and multivariable analyses were performed to determine factors associated with oncological and renal function outcomes.

Main Results:

• Seventy-four patients were analyzed with a median follow-up of 27.8 months. One-, 2-, and 4-year local failure rates were 5.85%, 7.77%, and 7.77%, respectively. Two-year cumulative incidence of distant metastasis was 4.24%.
• Lower planning target volume (PTV) mean dose and larger PTV were associated with increased local failure risk. Lower PTV maximum dose correlated with higher distant metastasis risk.
• Global eGFR decreased by a median of -7.0 ml/min at 1 year and -11.5 ml/min at 2 years. Ipsilateral renal function decreased from 47% to 36% at 2 years, with a compensatory increase in contralateral function. Higher volume of uninvolved renal cortex predicted a smaller eGFR decline.

Conclusions:

• SBRT provides favorable oncological outcomes for localized renal cell carcinoma in medically inoperable patients.
• A longitudinal decline in ipsilateral renal function post-SBRT is observed, accompanied by a compensatory increase in contralateral renal function.
• Clinical and dosimetric factors significantly influence both oncological control and renal function preservation after SBRT for RCC.