External-beam radiotherapy for clinically localized prostate cancer in Osaka, Japan, 1995-2006: time trends, outcome, and risk stratification

Abstract

Purpose: To establish an initial database of external-beam radiotherapy (EBRT) for clinically localized prostate cancer used in Osaka, Japan, and, by analyzing the results of the Osaka multicenter cooperative study, to determine time trends, outcome, and applicability of existing and the authors' original risk stratification methods.

Patients and methods: Data of 652 patients with clinically localized prostate cancer (T1-4 N0 M0) were accrued from July to December 2007. These patients had been treated from 1995 through 2006 with consecutive definitive EBRT of > or = 60 Gy at eleven institutions, mainly in Osaka. Altogether, 436 patients were eligible for analysis using several risk stratification methods, namely, those of D'Amico et al., the National Comprehensive Cancer Network (NCCN), and Seattle, as well as the authors' original Prostate Cancer Risk Index (PRIX).

Results: The number of patients showed a tenfold increase over 10 years, together with a rapid spread of the use of Gleason Score from 0% to > 90% of cases. The dominant RT dose fractionation was 70 Gy/35 fractions (87%). Hormone therapy had been administered to 95% of the patients and the higher PRIX corresponded to the higher rate of hormone usage. 3- and 5-year biochemical relapse-free survival (bRFS) rates were 85% and 70%, respectively. The D'Amico (p = 0.132), NCCN (p = 0.138), Seattle (p = 0.041) and PRIX (p = 0.044) classifications showed weak or no correlation with bRFS, while the own modified three-class PRIX (PRIX 0, 1-5, 6) showed a strong correlation (p = 0.002).

Conclusion: The use of prostate EBRT in Japan is still in its infancy, but is rapidly expanding. The short-term outcomes have been satisfactory considering the moderate RT dose. A very high rate of hormone usage may affect the outcome favorably, but also may compromise the usefulness of current risk stratification.