Image-Guided Stereotactic Body Radiation Therapy for Clinically Localized Prostate Cancer: Preliminary Clinical Results

Abstract

Stereotactic body radiotherapy (SBRT) is a new treatment modality for prostate cancer. The current study evaluates CyberKnife® SBRT and reports toxicity and early Prostate-Specific Antigen (PSA) kinetics. From June 2006 to August 2009, 45 low-and intermediate-risk prostate cancer patients received Cyberknife SBRT of 35 Gy in five fractions with 95% minimum target coverage. Median follow-up was 20-months (range 6–42-months). Seventeen patients received androgen-deprivation therapy also. Acute complications were mild, short-lived and no greater than Grade 2 by RTOG scale. Late toxicities consisted of one patient (2.2%) experiencing Grade 2 rectal, one patient (2.2%) Grade 3 and four patients (8.8%) with Grade 1 urinary toxicity. PSA in all patients progressively declined from a mean 4.7 ng/ml baseline to 1.48 ng/ml at three months, to 0.68 ng/ml at 12 months and to 0, 35 ng/ml at 24 months. The 28 hormon-naive patients had the mean PSA value of 1.1 ng/ml at one year from a mean 6.65 ng/ml baseline. There was a significant PSA value reduction in 11 hormone therapy patients with low baseline PSA value (< 1 ng/ml) from 0.37 down 0.14 ng/ml (p value 0.0068) at one year. Moreover, 14 low risk patients gave better results of mean PSA value than 17 Intermediate risk patients 0.43 ng/ml vs. 0.93 ng/ml (p value 0.02) at one year. No patient had biochemical failure at last follow-up. Hypofractionated SBRT appears to have potential against prostate cancer. Low toxicity and encouraging biochemical control support its use in early-stage prostate cancer. Results encourage further follow-up and larger studies.