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Hypofractionated stereotactic body radiation therapy as monotherapy for intermediate-risk prostate cancer

Andrew W Ju1, Hongkun Wang2, Eric K Oermann1, Benjamin A Sherer3, Sunghae Uhm1, Viola J Chen1, Arjun V Pendharkar3, Heather N Hanscom1, Joy S Kim1, Siyuan Lei1, Simeng Suy1, John H Lynch3, Anatoly Dritschilo1 and Sean P Collins1*

Author Affiliations

1 Department of Radiation Medicine, LL Bles Building, 3800 Reservoir Rd NW, Washington, DC 20007, USA

2 Department of Biostatistics, Bioinformatics, and Biomathematics, Georgetown University, Washington, DC, USA

3 Department of Urology, Georgetown University Hospital, Washington, DC, USA

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Radiation Oncology 2013, 8:30  doi:10.1186/1748-717X-8-30

Published: 31 January 2013

Abstract

Background

Hypofractionated stereotactic body radiation therapy (SBRT) has been advanced as monotherapy for low-risk prostate cancer. We examined the dose distributions and early clinical outcomes using this modality for the treatment of intermediate-risk prostate cancer.

Methods

Forty-one sequential hormone-naïve intermediate-risk prostate cancer patients received 35–36.25 Gy of CyberKnife-delivered SBRT in 5 fractions. Radiation dose distributions were analyzed for coverage of potential microscopic ECE by measuring the distance from the prostatic capsule to the 33 Gy isodose line. PSA levels, toxicities, and quality of life (QOL) measures were assessed at baseline and follow-up.

Results

All patients completed treatment with a mean coverage by the 33 Gy isodose line extending >5 mm beyond the prostatic capsule in all directions except posteriorly. Clinical responses were documented by a mean PSA decrease from 7.67 ng/mL pretreatment to 0.64 ng/mL at the median follow-up of 21 months. Forty patients remain free from biochemical progression. No Grade 3 or 4 toxicities were observed. Mean EPIC urinary irritation/obstruction and bowel QOL scores exhibited a transient decline post-treatment with a subsequent return to baseline. No significant change in sexual QOL was observed.

Conclusions

In this intermediate-risk patient population, an adequate radiation dose was delivered to areas of expected microscopic ECE in the majority of patients. Although prospective studies are needed to confirm long-term tumor control and toxicity, the short-term PSA response, biochemical relapse-free survival rate, and QOL in this interim analysis are comparable to results reported for prostate brachytherapy or external beam radiotherapy.

Trial registration

The Georgetown Institutional Review Board has approved this retrospective study (IRB 2009–510).

Keywords:
Stereotactic body radiotherapy; Prostate cancer; SBRT; CyberKnife; Intermediate-risk; Monotherapy; Hypofractionation