Used to define biochemical progression

The authors concluded that the favorable 3-year freedom from PSA failure in this group of high-risk patients suggested that trimodal therapy offered a significant improvement over standard monotherapy with radiation or radical prostatectomy alone. These results were supported by data on 72 men with high-risk disease (PSA level _ 10 ng/mL or Gleason score _ 7 or clinical stage _ T2c who underwent EBRT followed by palladium-103 brachytherapy boosts. All patients in this study underwent 8 months of combined androgen ablation with leuprolide and an oral antiandrogen beginning 3 months before initiation of EBRT. To allow for comparisons to contemporary literature, Kaplan-Meier survival curves were generated using three alternate definitions of biochemical recurrence: PSA level greater than 0.2 ng/mL, PSA level greater than 1.0 ng/mL, and three consecutive rising PSAs. Results indicate that when a PSA level greater than 0.2 ng/mL was used to define biochemical progression, 88% (95% confidence interval [CI] = 80– 97) of patients remained free of disease at 24 months. When a PSA level greater than 1.0 ng/mL was used, 97% (CI = 92–100) of patients remained disease free at 24 months. The three consecutive rise criteria yielded 90% (CI = 82– 98) recurrence-free survival at 24 months. Follow-up Postimplant dosimetry Adequate dose and coverage of the prostate is critical in reducing the incidence of local recurrence and minimizing acute and chronic toxicity. In 1999 and 2000, the ABS [43,45] published guidelines in an effort to standardize the recommended follow-up for patients treated with permanent I-125 or Pd-103 prostate implants. These guidelines covered all aspects of a patient’s care, including postimplant dosimetry analysis as well as timing of follow-up. All patients should undergo postimplant dosimetry to assess implant quality and to create a permanent record of the implant and the actual radiation dose delivered. Postimplant dosimetry should be CT based and the scan should be done 3 to 4 weeks after the surgery to allow for the resolution of postoperative edema. Standard implant quality indicators include Di, defined as the dose that covers i% of the prostate volume, and Vi, which is the fractional volume of the prostate that receives i% of the prescribed dose. For example, D100 is the dose that covers 100% of the prostate volume and V100 is the fractional volume of the prostate that receives 100% of the prescribed dose. The three values that should be reported are D90, D100, and V100. Parameters that should be obtained postimplant include examination of the isodose distribution, generation of the dose–volume histogram (DVH), and determination of dose uniformity and dose conformity indices. The isodose distribution plots offer the best assessment of prostate coverage and are generated from multiple CT slices through the prostate and adjacent structures. Methods for obtaining postimplant dosimetry include plain films, CT, and MRI. Plain films were the first method used to perform a geometric reconstruction. The problem with this method was that it could not visualize the prostate and adjacent structures. No information about the spatial relationship of the dose distribution to the prostate and surrounding tissues is available with this technique. The advantage of CT-based dosimetry was readily apparent based on the ability to determine seed location in relation to 740 E.M. Horwitz et al / Urol Clin N Am 30 (2003) 737–750 prostate and adjacent tissues. A potential limitation of CT-based dosimetry is the difficulty in reliably imaging the border of the prostate due to poor soft tissue contrast. Despite this potential disadvantage, CT-based imaging is the most common technique for postimplant dosimetry. Contiguous axial slices at 3 to 5 mm are obtained, including the prostate and, at minimum, a 2-cm margin superior and inferior to the prostate. It is particularly important to adequately image the urethra and anterior rectal wall. Because it is possible for a single seed to appear on multiple CT slices, a seed-sorting program is used to eliminate any duplication. A single plain film is used to determine the exact number of seeds implanted, because this number is necessary to use the seed-sorting program. MRI was introduced as a method for postimplant dosimetry based on the ability to clearly delineate soft tissue anatomy in several different planes.