Anatomy-based inverse planning dose optimization in HDR prostate implant: A toxicity study

Abstract

Background and purposeThe aim of this study is to evaluate the acute and late complications in patients who have received HDR implant boost using inverse planning, and to determine dose volume correlations. Patients and methodsBetween September 1999 and October 2002, 44 patients with locally advanced prostate cancer (PSA ≥10ng/ml, and/or Gleason score ≥7, and/or Stage T2c or higher) were treated with 40–45Gy external pelvic field followed by 2–3 fraction of inverse-planned HDR implant boost (6–9.5Gy /fraction). Median follow-up time was 1.7 years with 81.8% of patients who had at least 12 months of follow up (range 8.6–42.5. Acute and late morbidity data were collected and graded according to RTOG criteria. Questionnaires were used to collect prostate related measures of quality of life, and international prostate symptom score (IPSS) before and after treatment. Dose–volume histograms for prostate, urethra, bladder, penis bulb and rectum were analyzed. ResultsThe median patient age was 64 years. Of these, 32% were in the high risk group, and 61% in the intermediate risk group. 3 patients (7%) had no adverse prognostic factors. A single grade 3 GU acute toxicity was reported but no grade 3–4 acute GI toxicity. No grade 3–4 late GU or GI toxicity was reported. Acute (late) grade 2 urinary and rectal symptoms were reported in 31.8 (11.4%) and 4.6% (4.6%) of patients, respectively. A trend for predicting acute GU toxicity is seen for total HDR dose of more than 18Gy (OR=3.6, 95%CI=[0.96–13.5], P=0.058). The evolution of toxicity is presented for acute and late GU/GI toxicity. Erectile dysfunction occurs in approximately 27% of patients who were not on hormonal deprivation, but may be taking sildenafil. The IPSS peaked on averaged 6 weeks post-implant and returned to the baseline at a median of 6 months. ConclusionsInverse-planned HDR brachytherapy is a viable option to deliver higher dose to the prostate as a boost without increasing GU or rectal complication. Further HDR dose escalation to the prostate is feasible.