(ChemotherapyAdvisor) – Treatment of men with intermediate-risk organ-confined prostate cancer using five-day, non-invasive CyberKnife stereotactic body radiation therapy (SBRT) resulted in “excellent” biochemical control with mild toxicity and minimal impact on quality of life (QOL), according to a presentation at the American Urological Association Annual Meeting in Atlanta, GA.

“Median PSA levels compared favorably with other radiation modalities,” noted Alan Katz, MD, of Flushing Radiation Oncology, Flushing NY. While PSA nadir values suggest continued biochemical control, “further follow-up is needed to determine if these results remain durable in the long term.”

The prospective study evaluated SBRT efficacy and QOL in 81 patients with intermediate-risk (PSA 10–20ng/mL or Gleason=7) and organ-confined prostate cancer (70 T1c and 11 T2a, all N0M0). Mean age was 69.8 years; mean PSA was 8.3ng/mL. Androgen-deprivation therapy was administered to 23 patients for up to one year. Patients received a total dose of 35 or 36.26Gy delivered in five daily fractions; intrarectal amifostine was administered before each fraction.

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At a median follow-up of 46 months (range, 15–63 months) — including 24 patients with a minimum of five years of follow-up — median PSA was 0.10ng/mL. Six patients experienced biochemical failures, one locally. The four-year actuarial freedom from biochemical failure was 91%, Dr. Katz reported. Late RTOG toxicity was mild; 3.7% grade 2 rectal, 8.6% grade 2 urinary, and 1.2% grade 3 urinary adverse events occurred.

Mean EPIC urinary and bowel QOL declined at one month post-treatment and returned to baseline by two years, where it remained. Mean EPIC sexual QOL declined by 23% at one month, where it remained. The 77% of patients potent at baseline remained potent at last follow-up. Four patients died of other causes and three were lost to follow-up.

“Based on our study results, patients with intermediate-risk prostate cancer have an option for a less invasive alternative to invasive surgery or six to eight weeks of conventionally fractionated radiation therapy, that effectively and efficiently treats their cancer, while preserving their overall quality of life,” Dr. Katz said.

CyberKnife Prostate SBRT is manufactured by Accuray Inc., Sunnyvale, CA.

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