Analysis of intraprostatic failures in patients treated with hormonal therapy and radiotherapy: implications for conformal therapy planning.

PURPOSE: Conformal therapy of prostate cancer is based on high-dose irradiation to the entire prostate gland. The aim of this study was to analyze the pattern of intraprostatic recurrence in patients undergoing external beam radiotherapy (EBRT) at a dose of 65-70 Gy to evaluate whether conventional radiotherapy doses are adequate to control microscopic disease outside the primary tumor and therefore whether high-dose irradiation can be exclusively focused on the macroscopic disease. METHODS AND MATERIALS: The clinical and radiologic reports of 118 patients with prostate cancer undergoing EBRT (64.8-70.2 Gy) combined with hormonal therapy were evaluated. In all patients, before and after therapy, the size and site of the primary neoplasm within the prostate were assessed by clinical examination and imaging studies. RESULTS: With a median follow-up of 45 months (range 14-119), the 5-year actuarial local control rate was 83.9%. Twelve patients had an intraprostatic recurrence, with the appearance of a new nodule (in 5 patients with a complete response after therapy) or increased nodular size compared with the minimal size (in the 7 other patients). In all patients, on the basis of a semiquantitative evaluation of the site of recurrence, this was shown to originate within the initial tumor volume. CONCLUSION: The results of this analysis seem to confirm some histologic findings observed in patients undergoing prostatectomy for local recurrence after radiotherapy that suggest that local recurrence usually originates in the primary tumor rather than in focal prostatic intraepithelial neoplasia. This observation might justify the application of conformal therapy procedures aimed at identifying the gross tumor volume, in the phase of boost, exclusively with the primary tumor.