Dosimetric outcomes in prostate brachytherapy: Is downsizing the prostate with androgen deprivation necessary?

Gibbons, Erin P.; Jacobs, Bruce L.; Smith, Ryan P.; Beriwal, Sushil; Krishna, Komanduri; Benoit, Ronald M.

doi:10.1016/j.brachy.2008.11.009

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Volume 8, Issue 3 , Pages 304-308, July 2009

Dosimetric outcomes in prostate brachytherapy: Is downsizing the prostate with androgen deprivation necessary?

Erin P. Gibbons
- Department of Urology, University of Pittsburgh Medical Center, Pittsburgh, PA
- Department of Urology at the University of Toronto, Toronto, Canada
Bruce L. Jacobs
- Department of Urology, University of Pittsburgh Medical Center, Pittsburgh, PA
- Corresponding author. Department of Urology, University of Pittsburgh School of Medicine, 3471 Fifth Avenue, Pittsburgh, PA 15217. Tel.: +1-412-692-4100; fax: +1-412-692-4101.
Ryan P. Smith
- Department of Radiation Oncology, University of Pittsburgh Medical Center, Pittsburgh, PA
Sushil Beriwal
- Department of Radiation Oncology, University of Pittsburgh Medical Center, Pittsburgh, PA
Komanduri Krishna
- Department of Radiation Oncology, University of Pittsburgh Medical Center, Pittsburgh, PA
Ronald M. Benoit
- Department of Urology, University of Pittsburgh Medical Center, Pittsburgh, PA

Received 18 April 2008; received in revised form 31 October 2008; accepted 3 November 2008. published online 17 February 2009.

Abstract

Objectives

A large prostate volume has historically been a relative contraindication to prostate brachytherapy (PB) because of concerns of toxicity and potential pubic arch interference. Common practice has been to downsize large prostates with androgen deprivation therapy (ADT) before proceeding with brachytherapy. The present study compares postimplant dosimetry in patients with prostate volumes >50cc with those with prostate volumes ≤50cc.

Methods

A review of all patients who underwent PB at our institution from 2001 to 2006 was performed. Postimplant dosimetry was obtained approximately 4 weeks after brachytherapy.

Results

One-hundred forty-five out of a total of 148 patients had available dosimetry. In the 113 patients with prostate volumes ≤50cc (mean, 35.4cc, range, 14.2–49.7cc); the mean D₉₀ (dose which covers 90% of the prostate), V₁₀₀ (volume of prostate receiving 100% of the prescribed dose), V₁₅₀ (volume of prostate receiving 150% of the prescribed dose), and V₂₀₀ (volume of prostate receiving 200% of the prescribed dose) was 128.9%, 95.6%, 73.9%, and 51.2%, respectively. In the 32 patients with prostate volumes >50cc (mean 58.1cc, range 50.2–86.0cc); the mean D₉₀, V₁₀₀, V₁₅₀, and V₂₀₀ was 125.1%, 95.2%, 68.2%, and 41.7%, respectively. The rectal V₁₀₀ was 1.0cc for both cohorts. There was no statistically significant difference between the cohorts with respect to postimplant dosimetry for D₉₀, V₁₀₀, and V₁₅₀. The V₂₀₀ for prostate volumes >50cc was significantly lower (p<0.05).

Conclusions

In the present study, patients with prostate volumes >50cc have postimplant dosimetry parameters similar to patients with prostate volumes ≤50cc for D₉₀, V₁₀₀, and V₁₅₀; and significantly lower values for V₂₀₀. These results suggest that patients with large prostate volumes may not need to be routinely placed on hormonal therapy; sparing patients the side effects of hormonal therapy, and sparing the health care system the costs of luteinizing hormone-releasing hormone agonist injections.

Keywords: Prostate cancer, Prostate volume, Androgen deprivation, Brachytherapy