Stereotactic body radiotherapy for low-risk prostate cancer: five-year outcomes.

PURPOSE: Hypofractionated, stereotactic body radiotherapy (SBRT) is an emerging treatment approach for prostate cancer. We present the outcomes for low-risk prostate cancer patients with a median follow-up of 5 years after SBRT. METHOD AND MATERIALS: Between Dec. 2003 and Dec. 2005, a pooled cohort of 41 consecutive patients from Stanford, CA and Naples, FL received SBRT with CyberKnife for clinically localized, low-risk prostate cancer. Prescribed dose was 35-36.25 Gy in five fractions. No patient received hormone therapy. Kaplan-Meier biochemical progression-free survival (defined using the Phoenix method) and RTOG toxicity outcomes were assessed. RESULTS: At a median follow-up of 5 years, the biochemical progression-free survival was 93% (95% CI = 84.7% to 100%). Acute side effects resolved within 1-3 months of treatment completion. There were no grade 4 toxicities. No late grade 3 rectal toxicity occurred, and only one late grade 3 genitourinary toxicity occurred following repeated urologic instrumentation. CONCLUSION: Five-year results of SBRT for localized prostate cancer demonstrate the efficacy and safety of shorter courses of high dose per fraction radiation delivered with SBRT technique. Ongoing clinical trials are underway to further explore this treatment approach.

Stereotactic body radiotherapy: an emerging treatment approach for localized prostate cancer.

Here we report results from the first cohort of over 100 patients treated with hypofractionated, stereotactic body radiotherapy (SBRT) for early stage prostate cancer. Between February 2005 and December 2006, 112 patients with localized, biopsy-proven adenocarcinoma of the prostate (clinical stage T1cN0M0 to T2cN0M0) were treated in Naples, FL on a CyberKnife system (Accuray Incorporated, Sunnyvale, CA). Eighty-one patients had a Gleason score of 3+3. Mean initial PSA was 6.0, and mean initial prostate volume was 46.3cc. Implanted gold fiducials were used for image-guided targeting and tracking. Patients received 35-36 Gy administered in 5 consecutive fractions to the prostate and the proximal seminal vesicles, as identified on CT and MRI scans. At a median follow-up of 24 months, the mean PSA value was 0.78 ng/ml. Two patients have developed biopsy-confirmed local relapse; one developed distant metastases. Acute side effects were generally mild and resolved shortly after treatment. A single Grade 3 rectal complication was reported (bleeding). Eighty-two percent of patients who were sexually potent before treatment maintained erectile function post-treatment. Additional follow-up is required to better evaluate potential late toxicity and long-term PSA outcomes.