Phase II Trial of Stereotactic Ablative Radiation for Oligoprogressive Metastatic Kidney Cancer

BACKGROUND: Patients with metastatic renal cell carcinoma (mRCC) treated with systemic therapy sometimes progress at limited sites.The best treatment approach for patients with oligoprogression remains unclear. OBJECTIVE: To determine the ability of stereotactic ablative radiation (SAbR) to extend ongoing systemic therapy in mRCC patients with oligoprogression. DESIGN, SETTING, AND PARTICIPANTS: A single-arm phase II clinical trial was conducted at a university medical center and county hospital, including 20 patients with mRCC on first- to fourth-line systemic therapy with three or fewer sites of progression (including new sites) involving ≤30% of all sites. INTERVENTION: SAbR to oligoprogressing metastases at outset and longitudinally, while radiated sites remain controlled and overall disease oligoprogressive. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: The primary objective was to extend ongoing systemic therapy by >6 mo in >40% of patients. Secondary endpoints included overall survival, toxicity, and patient-reported quality of life. RESULTS AND LIMITATIONS: Twenty patients were enrolled. Upfront and sequential SAbR was administered to a total of 37 sites. The local control rate was 100%. At a median follow-up of 10.4 mo (interquartile range: 5.8-16.4), SAbR extended the duration of the ongoing systemic therapy by >6 mo in 14 patients (70%, 95% confidence interval [CI]: 49.9-90.1). The median time from SAbR to the onset of new systemic therapy or death was 11.1 mo (95% CI: 4.5-19.3). The median duration of SAbR-aided systemic therapy was 24.4 mo (95% CI: 15.3-42.2). Median overall survival was not reached. One patient developed grade 3 gastrointestinal toxicity possibly related to treatment. There was no significant decline in quality of life. Limitations include nonrandomized design and a small patient cohort. CONCLUSIONS: SAbR extended the duration of the ongoing systemic therapy for patients with oligoprogressive mRCC without undermining quality of life. These data support the evaluation of SAbR for oligoprogressive mRCC in a prospective randomized clinical trial. PATIENT SUMMARY: Patients with metastatic kidney cancer on systemic therapy but progressing at limited sites may benefit from focused radiation to progressive sites. Focused radiation was safe and effective, and extended the duration of the ongoing systemic therapy.