Stereotactic Radiotherapy for Oligoprogression in Metastatic Renal Cell Cancer Patients Receiving Tyrosine Kinase Inhibitor Therapy: A Phase 2 Prospective Multicenter Study

BACKGROUND: Despite the paucity of prospective evidence, stereotactic radiotherapy (SRT) is increasingly being considered in the setting of oligoprogression to delay the need to change systemic therapy. OBJECTIVE: To determine the local control (LC), progression-free survival (PFS), cumulative incidence of changing systemic therapy, and overall survival (OS) after SRT to oligoprogressive metastatic renal cell carcinoma (mRCC) lesions in patients who are on tyrosine kinase inhibitor (TKI) therapy. DESIGN, SETTING, AND PARTICIPANTS: A prospective multicenter study was performed to evaluate the use of SRT in oligoprogressive mRCC patients. Patients with mRCC who had previous stability or response after ≥3 mo of TKI therapy were eligible if they developed progression of five of fewer metastases. Thirty-seven patients with 57 oligoprogressive tumors were enrolled. INTERVENTION: Oligoprogressive tumors were treated with SRT, and the same TKI therapy was continued afterward. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Competing risk analyses and the Kaplan-Meir methodology were used to report the outcomes of interest. RESULTS AND LIMITATIONS: The median duration of TKI therapy prior to study entry was 18.6 mo; 1-yr LC of the irradiated tumors was 93% (95% confidence interval [CI] 71-98%). The median PFS after SRT was 9.3 mo (95% CI 7.5-15.7 mo). The cumulative incidence of changing systemic therapy was 47% (95% CI 32-68%) at 1 yr, with a median time to change in systemic therapy of 12.6 mo (95% CI 9.6-17.4 mo). One-year OS was 92% (95% CI 82-100%). There were no grade 3-5 SRT-related toxicities. CONCLUSIONS: LC of irradiated oligoprogressive mRCC tumors was high, and the need to change systemic therapy was delayed for a median of >1 yr. PATIENT SUMMARY: The use of stereotactic radiotherapy in metastatic kidney cancer patients, who develop growth of a few tumors while on oral targeted therapy, can significantly delay the need to change to the next line of drug therapy.