PubMed · 10699598
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J C Blasko. 2000. Brachytherapy.. https://doi.org/10.1016/s0090-4295(99)00472-0
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PURPOSE: The preplanned technique used for permanent prostate brachytherapy has limitations that may be overcome by intraoperative planning. The goal of the American Brachytherapy Society (ABS) project was to assess the current intraoperative planning process and explore the potential for improvement in intraoperative treatment planning (ITP). METHODS AND MATERIALS: Members of the ABS with expertise in ITP performed a literature review, reviewed their clinical experience with ITP, and explored the potential for improving the technique. RESULTS: The ABS proposes the following terminology in regard to prostate planning process: *Preplanning--Creation of a plan a few days or weeks before the implant procedure. *Intraoperative planning--Treatment planning in the operating room (OR): the patient and transrectal ultrasound probe are not moved between the volume study and the seed insertion procedure. * Intraoperative preplanning--Creation of a plan in the OR just before the implant procedure, with immediate execution of the plan. *Interactive planning--Stepwise refinement of the treatment plan using computerized dose calculations derived from image-based needle position feedback. *Dynamic dose calculation--Constant updating of dose distribution calculations using continuous deposited seed position feedback. Both intraoperative preplanning and interactive planning are currently feasible and commercially available and may help to overcome many of the limitations of the preplanning technique. Dosimetric feedback based on imaged needle positions can be used to modify the ITP. However, the dynamic changes in prostate size and shape and in seed position that occur during the implant are not yet quantifiable with current technology, and ITP does not obviate the need for postimplant dosimetric analysis. The major current limitation of ITP is the inability to localize the seeds in relation to the prostate. Dynamic dose calculation can become a reality once these issues are solved. Future advances can be expected in methods of enhancing seed identification, in imaging techniques, and in the development of better source delivery systems. Additionally, ITP should be correlated with outcome studies, using dosimetric, toxicity, and efficacy endpoints. CONCLUSION: ITP addresses many of the limitations of current permanent prostate brachytherapy and has some advantages over the preplanned technique. Further technologic advancement will be needed to achieve dynamic real-time calculation of dose distribution from implanted sources, with constant updating to allow modification of subsequent seed placement and consistent, ideal dose distribution within the target volume.
PURPOSE: To summarize longer-term postbrachytherapy morbidity in patients with prostate glands >50 cm3. METHODS AND MATERIALS: From 1997 to 1998, 33 patients with a transrectal ultrasound-based prostate volume >50 cm3 were treated at the University of Washington by 125I (144 Gy) or 103Pd (115 Gy) implantation for prostate carcinoma. These 33 patients comprised 7% of the total implant patient population. Twelve patients were treated with neoadjuvant androgen ablation before implantation. The (125)I source strength ranged from 0.34 to 0.5 mCi and the 103Pd source strength ranged from 1.1 to 1.4 mCi (pre-NIST-99). The total number of sources implanted was 94-223 (median 155). Despite the typical implant-related volume increase, the postimplant CT-defined prostate volumes were generally well-covered by the prescription isodose (median coverage 92%, range 80-100%). The preimplant urinary obstructive symptoms were quantified by the criteria of the American Urological Association. RESULTS: Of the 33 patients, 12 developed acute postimplant urinary retention, all presenting within 24 h of implantation. Patients who developed postimplant retention lasting >1 week were generally treated with intermittent self-catheterization. By 1 month, 85% of patients were catheter free. By 1 year, only 1 patient (4%) remained in urinary retention; the remainder of cases had resolved spontaneously. With follow-up of 1.7-2.6 years, the last American Urological Association scores were higher than the pretreatment scores in 15 patients and lower in 7 patients. No patient developed permanent urinary incontinence. Long-term changes in the American Urological Association scores were unrelated to whether the patient had been in urinary retention after implantation. Two patients developed rectal fistulas; they had preimplant transrectal ultrasound prostate volumes of 53 and 59 cm3, in the low range for this group of patients. No other patient had persistent rectal bleeding suggestive of clinically significant proctitis. The pretreatment serum prostate-specific antigen level was 3.3-15 ng/mL (median 7.2) and the last serum prostate-specific antigen level 0.1-1.6 ng/mL (median 0.2). CONCLUSION: Patients with larger prostate volumes appear to have moderate morbidity and a satisfactory technical outcome with brachytherapy. We do not believe the occurrence of two severe rectal complications was related to the prostate volume per se. Our experience and that of others calls into question the validity of using prostate volume as a criterion for patient suitability for prostate brachytherapy.
PURPOSE: To determine whether extraprostatic extension (EPE) can be treated by Pd-103 prostate implants. METHODS AND MATERIALS: The postimplant dosimetry of 22 consecutive Pd-103 prostate implants was analyzed to determine whether potential EPE was adequately treated. The implants were peripherally loaded and planned with a 3-5-mm dose margin at midgland. Seeds were not implanted outside of the capsule except at the base and apex. The postimplant dosimetry was based on a CT scan obtained 32 +/- 8 days postimplant. The radial distance between the prostate edge and the prescription isodose line was measured at the left lateral, left posterolateral, posterior, right posterolateral, and right lateral positions on each prostate contour. Similar measurements were made of the preplan dose margins. RESULTS: The mean postimplant dose margin was > or =4.5 mm at the midgland and apex of the prostate in agreement with the preplan. However, at the base, the mean margins at the five measurement locations were less than planned, typically ranging from 2.5 to 3.5 mm. The postimplant margin at the base was smaller than expected due to source placement errors, a correctable problem. CONCLUSIONS: Peripherally loaded Pd-103 prostate implants can deliver the prescription dose 3-5 mm outside the capsule, which is believed to be sufficient to treat 95-100% of EPE in favorable risk patients. However, dose coverage of EPE, like dose coverage of the prostate, is operator-dependent.