Use of Individual Fraction Size Data from 3756 Patients to Directly Determine the {alpha}/{beta} Ratio of Prostate Cancer

Journal Article · Tue May 01 04:00:00 EDT 2007 · International Journal of Radiation Oncology, Biology and Physics

DOI:https://doi.org/10.1016/j.ijrobp.2006.12.036· OSTI ID:20951611

Williams, Scott G ^[1]; Taylor, Jeremy M.G. ^[2]; Ning, Liu ^[2]; Tra, Yolande ^[3]; Duchesne, Gillian M ^[1]; Kestin, Larry L ^[4]; Martinez, Alvaro ^[4]; Pratt, Gary R ^[5]; Sandler, Howard ^[6]

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1. Division of Radiation Oncology, Peter MacCallum Cancer Centre and University of Melbourne, Melbourne, Victoria (Australia)
2. Department of Biostatistics, University of Michigan, Ann Arbor, MI (United States)
3. Department of Mathematics and Statistics, Rochester Institute of Technology, Rochester, NY (United States)
4. Department of Radiation Oncology, William Beaumont Hospital, Royal Oak, MI (United States)
5. Division of Radiation Oncology, Royal Brisbane Hospital, Brisbane, Queensland (Australia)
6. Department of Radiation Oncology, University of Michigan, Ann Arbor, MI (United States)

Purpose: To examine the effect of fraction size and total dose of radiation on recurrence of localized prostate cancer. Methods and Materials: A total of 3756 patients treated with radiation monotherapy at three institutions were analyzed, including 185 high-dose-rate brachytherapy (HDRB) boost patients. The 5th to 95th centiles of external beam radiotherapy (EBRT) fraction sizes and doses were 1.8 to 2.86 Gy, and 57.4 to 77.4 Gy, respectively, and HDRB fractional doses were between 5.5 and 12 Gy, totaling 147 unique fractionation schedules. Failure was defined by one biochemical (nadir + 2 ng/ml) and two advanced disease endpoints. The {alpha}/{beta} ratios were estimated via a proportional hazards model stratified by risk severity and institution. Results: The {alpha}/{beta} ratio using biochemical recurrence was 3.7 Gy (95% confidence interval [95% CI], 1.1, {infinity} Gy) for EBRT-only cases and 2.6 Gy (95% CI, 0.9, 4.8 Gy) after the addition of HDRB data. This estimate was highly dependent on an HDRB homogeneity correction factor (120% HDRB dose increase; {alpha}/{beta} ratio 4.5 Gy, 95% CI 1.6, 8.7 Gy). A 5-Gy increase in total dose reduced the hazard of failure by 16% (95% CI 11, 21%, p < 0.0001), and had more impact as follow-up matured (p < 0.0003). The clinically advanced endpoints concurred with the biochemical failure results, albeit with less precision. Conclusions: This study supports the concept that the {alpha}/{beta} ratio of prostate cancer is low, although considerable uncertainty remains in the estimated value. Outcome data from EBRT studies using substantially higher doses per fraction are needed to show increased precision in these estimates.

• OSTI ID: 20951611
• Journal Information: International Journal of Radiation Oncology, Biology and Physics, Journal Name: International Journal of Radiation Oncology, Biology and Physics Journal Issue: 1 Vol. 68; ISSN IOBPD3; ISSN 0360-3016
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
ACCURACY
BETA RATIO
BRACHYTHERAPY
CARCINOMAS
CORRECTIONS
DOSE RATES
FAILURES
HAZARDS
PATIENTS
PROSTATE
RADIATION DOSES
RADIOBIOLOGY