Factors influencing outcome of I-125 prostate cancer brachytherapy

Abstract

Brachytherapy is becoming an increasingly popular prostate cancer treatment, probably due to the specific advantages of the procedure, such as the minimal invasiveness and the lower chance of impotence and incontinence. Nonetheless, because of the long follow-up that is required to obtain prostate cancer related results, only recently a sufficient body of evidence has started to emerge to assess the cure rates of I125 prostate cancer brachytherapy. This thesis contributes to this body of evidence with long-term results, i.e. biochemical failure rates, prostate cancer specific survival and overall survival of a patient cohort treated with brachytherapy at the University Medical Center Utrecht in the last two decades. A strong association was found between several tumor characteristics, stratified into risk groups, and outcome as biochemical failure free survival and prostate cancer specific survival, the 10-year prostate cancer specific survival rates were, respectively, 96% for low risk, 87% for intermediate risk, and 69% for high risk prostate cancer. To aid clinicians and patients in choosing a curative prostate cancer treatment, nomograms have been developed that estimate the cancer free outcome probability after brachytherapy, prostatectomy or external beam radiotherapy. However, the predictive accuracy of nomograms, specifically when estimating the outcome after I-125 brachytherapy, is poor. This thesis concluded that, as long as the quality of the implant is optimal, primarily T stage, PSA at diagnosis and Gleason score seem to be associated with outcome, but not patients’ age or obesity. When combining these tumor characteristics in risk groups, results for low and intermediate risk are excellent with current standard of care. High risk prostate cancer, on the other hand, seem to be better off when treated in combination with external beam radiotherapy.