Dosimetric outcomes in prostate brachytherapy: is downsizing the prostate with androgen deprivation necessary?

Objectives: A large prostate volume has historically been a relative contraindication to prostate brachytherapy (PB) because of concerns of toxicity and potential pubic arch interference. Common practice has been to downsize large prostates with androgen deprivation therapy (ADT) before proceeding with brachytherapy. The present study compares postimplant dosimetry in patients with prostate volumes >50 cc with those with prostate volumes
Methods: A review of all patients who underwent PB at our institution from 2001 to 2006 was performed. Postimplant dosimetry was obtained approximately 4 weeks after brachytherapy.

Results: One-hundred forty-five out of a total of 148 patients had available dosimetry. In the 113 patients with prostate volumes 50 cc (mean 58.1 cc, range 50.2-86.0 cc); the mean D(90), V(100), V(150), and V(200) was 125.1%, 95.2%, 68.2%, and 41.7%, respectively. The rectal V(100) was 1.0 cc for both cohorts. There was no statistically significant difference between the cohorts with respect to postimplant dosimetry for D(90), V(100), and V(150). The V(200) for prostate volumes >50 cc was significantly lower (p<0.05).

Conclusions: In the present study, patients with prostate volumes >50 cc have postimplant dosimetry parameters similar to patients with prostate volumes