- 作者：Cé ; cile Proust-Lima ; Jeremy M.G. Taylor ; Solè ; ne Sé ; cher ; Howard S ; ler ; Larry Kestin ; Tom Pickles ; Kyoungwha Bae ; Roger Allison ; Scott Williams
- 刊名：International Journal of Radiation Oncology*Biology*Physics
- 出版年：2011
- 出版时间：1 January 2011
- 年：2011
- 卷：79
- 期：1
- 页码：195-201
- 全文大小：126 K
Purpose
To estimate the α/β ratio of prostate cancer treated with external beam radiation only by use of a model of long-term prostate-specific antigen (PSA) dynamics.Methods and Materials
Repeated measures of PSA from 5,093 patients from 6 institutions treated for localized prostate cancer by external beam radiation therapy (EBRT) without planned androgen deprivation were analyzed. A biphasic linear mixed model described the post-treatment evolution of PSA, rather than a conventional model of time to biochemical recurrence. The model was adjusted for standard prognostic factors (T stage, initial PSA level, and Gleason score) and cohort-specific effects. The radiation dose fractionation effect was estimated from the long-term rate of rise of PSA level.
Results
Adjusted for other factors, total dose of EBRT and sum of squared doses per fraction were associated with long-term rate of change of PSA level (p = 0.0017 and p = 0.0003, respectively), an increase of each being associated with a lower rate of rise. The α/β ratio was estimated at 1.55 Gy (95 % confidence band, 0.46–4.52 Gy). This estimate was robust to adjustment of the linear mixed model.
Conclusions
By analysis of a large EBRT-only cohort along with a method that uses all the repeated measures of PSA after the end of treatment, a low and precise α/β was estimated. These data support the use of hypofractionation at fractional doses up to 2.8 Gy but cannot presently be assumed to accurately represent higher doses per fraction.