Analysis of biopsy findings and implant quality following ultrasonically-guided 125I implantation for localised prostatic carcinoma.

Transperineal ultrasound-guided 125I implantation was undertaken in 52 patients with localised prostate cancer. After implantation, ultrasound-guided biopsies were taken from the previous malignant areas every 6 months in all patients. The percentage of negative biopsies increased from 22% at 6 months to 50% at 48 months. Implant quality was analysed in 37 patients. The difference between isodose levels encompassing the prostate and the aimed levels of 160 Gy was taken as a measure of implant quality. A good quality implant (< 10% underdosage) was found in 43% of patients, a moderate quality (10-25% underdosage) in 35%, and a poor quality implant (> 25% underdosage) in 22%. A statistically significant correlation was found between the quality of the implant and resulting negative biopsy at the original tumour site. Determination of prostate specific antigen (PSA) was not possible from the beginning of the study but an analysis with biopsy findings, implant quality and prostate volume reduction during follow-up has been performed since 1989. A significant correlation was observed between implant quality and serum PSA, and also between volume reduction and serum PSA.