External beam radiotherapy dose response of prostate cancer

Alan Pollack, Gunar K. Zagars

Research output: Contribution to journalArticle

197 Scopus citations

Abstract

Purpose: To determine the external beam radiotherapy dose response of palpable Stage T1-T4, mostly Nx, patients with adenocarcinoma of the prostate. Methods and Materials: There were 938 men consecutively treated between 1987 and 1995 who had pretreatment prostate specific antigen (PSA) levels. Posttreatment failure was defined as disease recurrence and/or two elevations in PSA on consecutive follow-up visits. The radiotherapy technique consisted of a four-field box with a small four-field reduction after 46 Gy in 844 patients (total dose of 60-70 Gy) or with a six-field conformal boost after 46 Gy in 94 patients (total dose of 74-78 Gy). Neoadjuvant or adjuvant androgen ablation was not used in any patient. Median follow-up was 40 months. Results: The mean and median radiotherapy doses for the entire group were 67.8 ±13.3 Gy (±SEM) and 66 Gy. The mean radiotherapy dose was higher in those who had Stage T3/T4 disease, Gleason scores of 8-10, or pretreatment PSAs of >4 ng/ml. In general, patients with more aggressive pretreatment prognostic features were treated to higher doses; yet, those that relapsed or had a rising PSA were treated to significantly lower doses. Actuarial analyses were facilitated by dividing patients into three dose groups: ≤67, >67-77, and >77 Gy. The actuarial freedom from failure rates at 3 years were 61, 74, and 96% for the low, intermediate, and high dose groups. Stratification of the patients by pretreatment PSA revealed that dose was a significant correlate of freedom from relapse or a rising PSA for those with PSAs >4-10, >10-20, and >20 ng/ml. The only patients in which an improvement in outcome was not related to higher doses were those with a pretreatment PSA ≤4 ng/ml. Dose was significantly associated with freedom from failure for Stage T1/T2 and Stage T3/T4 patients, as well as for those stratified by Gleason score. Multivariate analysis using Cox proportional hazards models showed that dose was on independent and highly significant predictor of relapse or a rising PSA. Conclusion: This retrospective review strongly indicates that radiotherapy dose to the prostate is critical to the cure of prostate cancer, even for favorable patients with pretreatment PSAs of >4-10 ng/ml, Stages T1/T2, or Gleason scores of 2-6. Final confirmation awaits the results of our randomized trial.

Original languageEnglish (US)
Pages (from-to)1011-1018
Number of pages8
JournalInternational Journal of Radiation Oncology Biology Physics
Volume39
Issue number5
DOIs
StatePublished - Dec 1 1997
Externally publishedYes

Keywords

  • Dose
  • Prostate-specific antigen
  • Radiotherapy

ASJC Scopus subject areas

  • Oncology
  • Radiology Nuclear Medicine and imaging
  • Radiation

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