Fumitaka Ito MD, Presenter: Nothing to Disclose

Hidetoshi Kobayashi MD, PhD, Abstract Co-Author: Nothing to Disclose

Yumi Oie, Abstract Co-Author: Nothing to Disclose

Hidekazu Hattori MD, Abstract Co-Author: Nothing to Disclose

Hiroshi Toyama, Abstract Co-Author: Nothing to Disclose

Masayuki Ito, Abstract Co-Author: Nothing to Disclose

Purpose:Excellent biochemical relapse free survival with low dose rate I-125 brachytherapy for patients with early prostate cancer is demonstrated. Dose escalation may be feasible, but the balance between tumor control and normal tissue damage is critical to outcome and morbidity. Dose delivered to 90% of prostate is reported to be closely correlated with outcome. Low delivered dose is one of the origin of recurrence, so inhomogeneity is suspected to be important predictor. In this paper, the relation between biochemical failure free survival and dose inhomogeneity were evaluated.Material and methods:Five hundred twenty nine prostate cancer patients were treated by permanent brachytherapy using I-125 seeds from 2006 to 2012. PSA failure was determined according to the Phoenix definition. The prescription dose was: low risk 160Gy brachytherapy only in low risk, 110Gy brachytherapy after 45Gy adjuvant EBRT intermediate risk and high risk. These grouping is from risk classification described by D’Amico.Results:Twenty three patients showed PSA failure. In 23, 14 are under observation, 7 patients were treated with endocrine therapy, and 2 patients underwent operation of robot assisted radical prostatectomy (by da Vinci S).The pathologically proved recurrence lesions were coincided with cold dose areas of post-plan. In order to evaluate the relation between dose insufficiency and recurrence, the prostate DVH of biological failure patients were compared with that of control cases, who were free from PSA failure. The prostate DVH of biological failure patients showed lower dose curve compared with the control cases, at points from V80 to V200 in prostate DVH.Conclusion:Dose inhomogeneity is one of the reason of biological failure of permanent prostate brachytherapy. Ratio of volume of prostate receiving 100% or 150% of prescribed dose (V100, V150), which are indexes of homogeneity, are important indexes.

Ito, F, Kobayashi, H, Oie, Y, Hattori, H, Toyama, H, Ito, M, Analysis of the Relationship between Dose Inhomogeneity and Local Control in Patients with Prostate Cancer Treated with Permanent Seeds Brachytherapy.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14042030.html