Objective: To evaluate acute toxicity outcomes of prostate cancer patients treated with CyberKnife-delivered hypofractionated radiotherapy.
Methods: This study was a retrospective chart review analysis of the first 50 patients treated with CyberKnife radiotherapy for prostate cancer. Most patients were affected with early to intermediate stage prostate cancer. Two patients had metastatic disease at presentation and were excluded. A total of 37 patients received irradiation at a dose of 35 to 37.5 Gy in 5 fractions of 7 to 7.5 Gy per fraction. Assuming an alpha/beta ratio of 1.5 Gy, this process delivered an equivalent dose of 85 to 96 Gy in 2 Gy fractions (EQD2). A subset of patients (n = 11) received standard linear accelerator-based pelvic radiation treatment either by intensity modulated radiation therapy or tomotherapy and received a boost via the CyberKnife at a dose of 17.6 to 25 Gy in 2 to 5 fractions (EQD2= 46.6-72 Gy). The acute toxicities were recorded using the Common Terminology Criteria for Adverse Events, version 3.0, throughout treatment and at patients' follow-up visits.
Results: The median patient age at presentation was 66 years (range, 46-80). The mean pretreatment prostate specific antigen and Gleason scores were 9.16 ng/mL and 7, respectively. Grade 2 acute genitourinary toxicity was reported by 10% of patients (n = 5). Only 3 patients reported grade 3 acute genitourinary toxicity. No gastrointestinal grade 2 or grade 3 toxicities were reported.
Conclusions: CyberKnife-delivered hypofractionated radiotherapy for the treatment of prostate cancer has an acceptable acute toxicity profile.