A descriptive analysis of postimplant dosimetric parameters from Radiation Therapy Oncology Group P0019

Lee, W. Robert; Bae, Kyounghwa; Lawton, Colleen A.; Gillin, Michael T.; Morton, Gerard; Firat, Selim; Baikadi, Madhava; Kuettel, Michael; Greven, Kathryn; Sandler, Howard

doi:10.1016/j.brachy.2006.08.005

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Volume 5, Issue 4 , Pages 239-243, October 2006

A descriptive analysis of postimplant dosimetric parameters from Radiation Therapy Oncology Group P0019

W. Robert Lee
- Department of Radiation Oncology, Duke University Medical Center, Durham, NC
- Corresponding author. Department of Radiation Oncology, Duke University Medical Center, Science Dr., Rm. 05151, Box 3085, Morris Building, Durham, NC 27710. Tel.: +1-919-668-7342; fax: +1-919-668-7345.
Kyounghwa Bae
- Department of Radiation Oncology, Radiation Therapy Oncology Group, Philadelphia, PA
Colleen A. Lawton
- Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, WI
Michael T. Gillin
- Department of Radiation Oncology, MD Anderson Hospital, Houston, TX
Gerard Morton
- Department of Radiation Oncology, Toronto-Sunnybrook Regional Cancer Centre, Toronto, ON, Canada
Selim Firat
- Albert Einstein School of Medicine, Philadelphia, PA
Madhava Baikadi
- Albert Einstein School of Medicine, Philadelphia, PA
Michael Kuettel
- Department of Radiation Medicine, Roswell Park Cancer Center, Buffalo, NY
Kathryn Greven
- Department of Radiation Oncology, Wake Forest University, Winston-Salem, NC
Howard Sandler
- Department of Radiation Oncology, University of Michigan, Ann Arbor, MI

Received 5 June 2006; received in revised form 21 August 2006; accepted 21 August 2006.

Abstract

Background

To date, there are few descriptive analyses of postimplant dosimetry from multi-institutional clinical trials. The purpose of this report is to describe the postimplant dosimetry achieved in Radiation Therapy Oncology Group (RTOG) 0019.

Methods and materials

Patients were treated with external beam radiation therapy (45Gy/25 fractions) followed by a prostate implant (I-125, prescription dose 108Gy). Postimplant dosimetric assessment was accomplished by obtaining a CT scan of the prostate 1 month after the date of the implant procedure. Prostate volume was outlined by the first author. Dose–volume histograms were calculated by the Radiologic Physics Center. Four dosimetric quantifiers (DQs) were examined: D₉₀ is the dose (reported as percentage of the prescription dose) received by 90% of the prostate; V₁₀₀, V₁₅₀, V₂₀₀ is the percentage of the prostate volume receiving 100%, 150%, and 200% of the prescription dose, respectively. For the purposes of analysis, institutions were divided into three groups according to accrual (<5, 6–9, 10–12).

Results

One hundred thirty-eight patients from 27 institutions were registered in the study. Nineteen patients were excluded from this analysis; 14 who had no data and 5 who were ineligible, leaving 119 for analysis. The mean, median, and range of the four DQs are as follows: D₉₀ 105.6%, 106.0%, 57.6–174.8%; V₁₀₀ 89.8%, 92.6%, 11.2–100%; V₁₅₀ 58.4%, 59.6%, 0.9–93.7%; and V₂₀₀ 27.9%, 25.1%, 0.3–85.2%. Statistically significant differences according to institutional accrual were observed for D₉₀ (p=0.0283) and V₂₀₀ (p=0.0075), but not for V₁₀₀ (p=0.1534) and V₁₅₀ (p=0.0509).

Conclusions

The DQ observed in this multi-institutional prospective study are roughly comparable to series from single institutions with considerable brachytherapy experience. Differences in DQs were observed according to institutional accrual. These data could be used to determine a community standard with respect to postimplant dosimetry.

Keywords: Brachytherapy, Prostate cancer, I-125, dosimetry