Research on improvement of precision in high-dose-rate brachytherapy for prostate cancer

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From May 1995 through December 2005, 122 patients with prostate cancer were treated with high-dose-rate brachytherapy as monotherapy (i.e. without external beam radiotherapy) at Osaka University Hospital. The median follow-up time was 33 months (range, 6-129). Most of the patients were treated with 54 Gy/9 fractions/5 days, which corresponded to 116 Gy with 2 Gy/fraction on the assumption of a/β =1.5 Gy using LQ model. The 5-year overall survival rate for all patients was 94%, local control rate 97%, and PSA control rate 77%. The 5-year PSA control rates for low-, intermediate-, and high-risk groups were 91%, 92%, and 67%, respectively. Acute Grade 3 toxicity was observed in 6 patients, Grade 2 in 24 patients, and Grade 1 in 59 patients. Late Grade 3 toxicity was observed in 2 patients, Grade 2 in 13 patients, and Grade 1 in 28 patients. High-dose-rate brachytherapy with our regimen was feasible and its toxicity acceptable. The preliminary and interim results were both comparable with other literature. Because it can treat even extracapsular lesion and because it can administer a high dose to the prostate, it was suggested that high-dose-rate brachytherapy as monotherapy was effective to the locally advanced prostate cancer.In the field of treatment planning process, we showed superiority of Anatomy-based dwell positions, where dwell positions were arranged according to the figure of prostate to conventional cylindrical dwell positions; and also superiority of Inverse optimization. Second, we applied our original Attraction-Repulsion Model, and showed a possibility that the new algorithm overcame commercial-based ones.We also invented and reported a new method that enabled the patients to walk around while they were implanted the needles for brachytherapy, with the intention to improve their quality of life during treatment when otherwise they should be on bed for 4 or 5 days.