The efficacy and safety of stereotactic body radiotherapy combined with systematic therapy for metastatic renal cell carcinoma: a systematic review and meta-analysis

There is considerable interest in the potential of stereotactic body radiation therapy (SBRT) combined with systemic therapy such as tyrosine kinase inhibitors (TKIs) or immune checkpoint inhibitors (ICIs). However, its efficacy and safety remain unclear. The purpose of this study was to evaluate the efficacy and safety of conducting SBRT during ICI or TKI treatment in different disease settings for patients with metastatic renal cell carcinoma (mRCC). A total of 16 studies were ultimately included. Under the random effects model, the pooled 1-year local control rate (1-yr LCR) and objective response rate (ORR) were 90% (95% confidence interval [CI]: 80%-95%, I2 = 67%) and 52% (95% CI: 37%-67%, I2 = 90%), respectively. SBRT concomitant with different systemic therapy yield significant different 1-yr LCR (p < 0.01) and ORR (p = 0.02). Regarding survival benefits, the pooled 1-year progression-free survival (1-yr PFS) and 1-year overall survival (1-yr OS) rates were 45% (95% CI: 29%-62%, I2 = 91%) and 85% (95% CI: 76%-91%, I2 = 66%), respectively. 1-yr PFS and 1-yr OS in different disease settings demonstrated significant difference (p < 0.01). As for toxicity, the pooled incidence of grade 3-4 adverse events was 14% (95% CI: 5%-26%, I2 = 90%). This study highlights the feasibility of utilizing these strategies in mRCC patients, especially those with a low metastatic tumor burden.