Four of 27 patients were excluded from the evaluation. One was excluded due to a technical failure during implant, and three patients were excluded because the balloon prematurely deflated. The balloon status was evaluated for the duration of the radiotherapy period in 23 patients. With the balloon implant, the distance between the prostate and rectum increased 10-fold, from a mean 0.22 +/- 0.2 cm to 2.47 +/- 0.47 cm. During the radiotherapy period the balloon length changed from 4.25 +/- 0.49 cm to 3.81 +/- 0.84 cm and the balloon height from 1.86 +/- 0.24 cm to 1.67 +/- 0.22 cm. But the prostate-rectum interspace distance remained constant from beginning to end of radiotherapy: 2.47 +/- 0.47 cm and 2.41 +/- 0.43 cm, respectively. A significant mean reduction in calculated rectal radiation exposure was achieved. The implant procedure was well tolerated. The adverse events included mild pain at the perineal skin and in the anus. Three patients experienced acute urinary retention which resolved in a few hours following conservative treatment. No infections or thromboembolic events occurred during the implant procedure or during the radiotherapy period.

The transperineal implantation of the biodegradable balloon in patients scheduled to receive radiotherapy was safe and achieved a significant and constant gap between the prostate and rectum. This separation resulted in an important reduction in the rectal radiation dose. A prospective study to evaluate the acute and late rectal toxicity is needed.