Phase I-II study of intraoperative radiation therapy (IORT) after radical prostatectomy for prostate cancer

Recent studies have suggested an alpha/beta ratio in prostate cancer of 1.5-3 Gy, which is lower than that assumed for late-responsive normal tissues. Therefore the administration of a single, intraoperative dose of irradiation should represent a convenient irradiation modality in prostate cancer.

Between February 2002 and June 2004, 34 patients with localized prostate cancer with only one risk factor (Gleason score > or =7, Clinical Stage [cT] > or =2c, or prostate-specific antigen [PSA] of 11-20 ng/mL) and without clinical evidence of lymph node metastases were treated with radical prostatectomy (RP) and intraoperative radiotherapy on the tumor bed. A dose-finding procedure based on the Fibonacci method was employed. Dose levels of 16, 18, and 20 Gy were selected, which are biologically equivalent to total doses of about 60-80 Gy administered with conventional fractionation, using an alpha/beta ratio value of 3.

At a median follow-up of 41 months, 24 (71%) patients were alive with an undetectable PSA value. No patients died from disease, whereas 2 patients died from other malignancies. Locoregional failures were detected in 3 (9%) patients, 2 in the prostate bed and 1 in the common iliac node chain outside the radiation field. A PSA rise without local or distant disease was observed in 7 (21%) cases. The overall 3-year biochemical progression-free survival rate was 77.3%.

Our dose-finding study demonstrated the feasibility of intraoperative radiotherapy in prostate cancer also at the highest administered dose.