Stereotactic interstitial radiosurgery with the Photon Radiosurgery System (PRS) for metastatic brain tumors: a prospective single-center clinical trial.

PURPOSE: To evaluate the efficacy and the treatment outcome of tumor patients being treated stereotactically with a miniature X-ray generator (Photon Radiosurgery System, PRS). METHODS AND MATERIALS: Thirty-five patients with histologically diagnosed cerebral metastases were treated with a single fraction of stereotactic interstitial irradiation (median, 18 Gy). Clinical and neuroimaging evaluation were assessed at 2-, 6-, and 12-week intervals postoperatively and every 3 months thereafter. Survival, local control, and distant and overall brain freedom from progression were obtained using the Kaplan-Meier method. RESULTS: Median survival was 7.37 months and the actuarial survival rates at 6 and 12 months were 60.0% and 34.3%, respectively. Acute complications on six patients were associated with shorter survival. Local tumor control at the initial stage and at the last follow-up were 82% and 50%. Eighteen patients (53%) developed distant brain metastases after treatment. At 1 year, the local control rate and distant and overall brain freedom from progression were 33.0%, 43.3%, and 14.7%, respectively. A shorter local tumor control was observed by PRS treatment of a recurrent tumor and by irregular tumor configuration. CONCLUSIONS: Interstitial radiosurgery with the PRS requires continued investigation. It allows for an immediate and potentially cost-efficient treatment for patients with singular, small (