Severe rectal complications after prostate brachytherapy.

PURPOSE: Some investigators have reported severe rectal complications after brachytherapy. Due to the low number of such events, their relationship to dosimetric parameters has not been well characterized. METHODS AND MATERIALS: A total of 3126 patients were treated with low dose rate brachytherapy from 1998 through 2010. 2464 had implant alone, and 313 had implant preceded by 44-46Gy supplemental external beam radiation (EBRT). Post-implant dosimetry was based on a CT scan obtained on the day of implant, generally within 30min of the procedure. Every patient's record was reviewed for occurrence of rectal complications. RESULTS: Eight of 2464 patients (0.32%) treated with brachytherapy alone developed a radiation-related rectal fistula. Average prostatic and rectal dose parameters were moderately higher for fistula patients than for patients without a severe rectal complication. For instance, the average R100 was 1.2±0.75cc for fistula patients, versus 0.37±0.88cc for non-fistula patients. However, the fistula patients' values were well within the range of values for patients without a rectal complication. Four patients had some attempt at repair or reconstruction, but long-term functional outcomes were not favorable. CONCLUSIONS: Rectal fistulas are a very uncommon potential complication of prostate brachytherapy, which can occur even in the setting of acceptable day 0 rectal doses. Their occurrence is not easily explained by standard dosimetric or clinical factors.

Extraprostatic seed placement and its effect on seed loss.

PURPOSE: The purpose of this study was to examine the relationship between extraprostatic seed placement and seed loss in a cohort of patients who had underwent both computed tomographic (CT) and magnetic resonance (MR) scans at day 0 and day 30 following brachytherapy. MATERIALS AND METHODS: Twenty-two patients with 1997 AJC clinical stage T1-T2 prostatic carcinoma were implanted with nonstranded I 125. Patients were selected solely by having a prostate volume between 15 and 60 cc and a willingness to return for 30-day follow-up CT and MR scans. The total number of I-125 sources implanted on day 0 ranged from 50 to 104 (median: 70). Preplan treatment planning methods have been previously described in detail: a modified peripheral loading pattern and treatment margins of 5-10 mm were used. Noncontrast postimplantation CT and MR scans were obtained 1-4 hours after implantation on day 0. The total seed count on days 0 and 30 was verified by plain radiograph. Pelvic MR (T1) images were registered with the CT images in the Varian planning system, using bony landmarks. The number of extracapsular seeds in each quadrant of the circumference was then totaled for each patient. A second set of plain radiographs (for seed counting), as well as CT and MR scans, were obtained 30 days after implantation (day 30) and were similarly analyzed. RESULTS: The number of extraprostatic seeds at day 0 ranged from 13 to 35, making up 17%-48% (median: 34%) of the total number implanted. Of the 22 patients, 10 lost one or more seeds between the implantation day and the 1-month follow-up. The mean number of seeds lost was 1.1 (+/- 1.7). There was no apparent relationship between the percent of extraprostatic seeds and the number of seeds lost. There was no apparent relationship between seed loss and number of seeds less than 3 mm or greater than 3 mm from the prostatic capsule. CONCLUSIONS: We have shown here that with CT and MR seed localization, extraprostatic seed placement does not appear to substantially increase the likelihood of seed loss after the procedure.