Long term results of a prospective dose escalation phase-II trial: Interstitial pulsed-dose-rate brachytherapy as boost for intermediate- and high-risk prostate cancer

Abstract

PurposeWe reviewed our seven year single institution experience with pulsed dose rate brachytherapy dose escalation study in patients with intermediate and high risk prostate cancer. Materials and methodsWe treated a total of 130 patients for intermediate and high risk prostate cancer at our institution between 2000 and 2007 using PDR-brachytherapy as a boost after conformal external beam radiation therapy to 50.4Gy. The majority of patients had T2 disease (T1c 6%, T2 75%, T3 19%). Seventy three patients had intermediate-risk and 53 patients had high-risk disease according to the D’Amico classification. The dose of the brachytherapy boost was escalated from 25 to 35Gy – 33pts. received 25Gy (total dose 75Gy), 63pts. 30Gy (total dose 80Gy) and 34pts. 35Gy, (total dose 85Gy) given in one session (dose per pulse was 0.60Gy or 0.70Gy/h, 24h per day, night and day, with a time interval of 1h between two pulses). PSA-recurrence-free survival according to Kaplan–Meier using the Phoenix definition of biochemical failure was calculated and also late toxicities according to Common Toxicity Criteria scale were assessed. ResultsAt the time of analysis with a median follow-up of 60months biochemical control was achieved by 88% of patients – only 16/130 patients (12.3%) developed a biochemical relapse. Biochemical relapse free survival calculated according to Kaplan–Meier for all patients at 5years was 85.6% (83.9% for intermediate-risk patients and 84.2% for high-risk patients) and at 9years’ follow up it was 79.0%. Analysing biochemical relapse free survival separately for different boost dose levels, at 5years it was 97% for the 35Gy boost dose and 82% for the 25 and 30Gy dose levels. The side effects of therapy were negligible: There were 18 cases (15%) of grade 1/2 rectal proctitis, one case (0.8%) of grade 3 proctitis, 18 cases (15%) of grade 1/2 cystitis, and no cases (0%) with dysuria grade 3. No patient had a bulbourethral stricture requiring dilation or new onset incontinence. ConclusionsImage-guided conformal PDR-brachytherapy using up to 35Gy as boost dose after 50Gy of external beam radiation therapy (total dose up to 85Gy) is a very effective treatment option with very low morbidity in patients with intermediate or high risk prostate cancer. Further dose escalation seems possible.