Analysis of serial CT scans to assess template and catheter movement in prostate HDR brachytherapy.

PURPOSE: As prostate high-dose-rate (HDR) brachytherapy becomes more prevalent, varying amounts of catheter displacement have been noted. To investigate the constancy of catheter position and its impact on dose distribution, we analyzed serial dosimetric CT scans. METHODS AND MATERIALS: The data from 50 patients were analyzed. During initial CT treatment planning, transverse images of the implant volume were collected, and all structures were digitized into the Nucletron Brachytherapy Planning System. Digitally reconstructed radiographs were generated with rendering of the catheter tips, ischial tuberosity, and perineal template. The distance from each catheter tip to the template and to the ischial tuberosity was measured. The distance between the ischial tuberosity and the template was similarly measured. A second CT set was obtained at different intervals and compared with the first measurement to assess catheter and/or template movement. In 10 patients, the second CT set was obtained before the third fraction in both 2-mm and 5-mm slice sequences, and the latter was used to re-create the HDR plan. RESULTS: Although no interfraction catheter movement relative to the template was found, the template-catheter unit moved in a caudal direction between HDR fractions. The amount of displacement was time dependent: 2 mm before the second fraction, 8 mm before the third, and 10 mm before the fourth. When comparing the first HDR treatment with the third, median decreases in the following dosimetric parameters were noted: dose to 90% of the prostate volume, 35% (r = 0-60); minimal dose to the base, 35% (r = 17-65); and maximal dose to 1 cm(3), 13% (r = 3-19%). CONCLUSION: The interstitial catheters did not slip within the template and were not caudally displaced independently but rather in conjunction with the template. The displacement occurred in a time-dependent fashion, and, without redress, significant dosimetric changes are encountered by the third fraction.

The effects of edema on urethral dose following palladium-103 prostate brachytherapy.

The effects of edema on urethral dose after interstitial prostate brachytherapy with palladium-103 (103Pd) were studied. Fifty patients underwent a 90-Gy 103Pd implant followed by dosimetric computed tomography (CT). Twenty-one days later, a Foley catheter was reinserted and a dosimetric CT was repeated. The mean reduction in prostate volume between day 0 and day 21 was 16%. Median prostate D90 on day 0 was 89.7 Gy (range 59.5 to 127) and 99.5 Gy (range 62.5 to 130) on day 21. Median prostate V100 was 90% (range 63 to 98%) on day 0 and 96% (range 66 to 99%) on day 21. Median V150 was 61% (range 31 to 85%) on day 0 and 75% (range 39 to 93%) on day 21. Median urethral D50 was 107 Gy (range 57 to 201) on day 0 and 126 Gy (range 64 to 193) on day 21. Regression analysis demonstrated a significant correlation between the decrease in the prostate volume and the increased urethral D50 (r 0.58, p < 0.05). Acute urinary toxicity was 32% grade 0, 38% grade 1, and 30% grade 2. The median urethral D50 increased by a mean of 18% with a correlation coefficient of 0.58 (p < 0.05). Catheterization of the urethra was well tolerated and was of value in better characterizing urethral dose after 103Pd brachytherapy.

Endobronchial brachytherapy and external-beam radiotherapy in patients with endobronchial obstruction and extrabronchial extension.

PURPOSE: To evaluate the efficacy of high-dose rate endobronchial brachytherapy (HDR-EB) with concomitant short-course external-beam radiotherapy (EBRT) in patients with both endobronchial and extrabronchial tumor. METHODS AND MATERIALS: Patients with endobronchial disease and extrabronchial lesions greater than 2.5cm were treated with three 5Gy HDR-EB and 37.5Gy EBRT delivered over 3.5 weeks. Flexible fiberoptic bronchoscopy was performed with the patient under conscious sedation, and tumor location, length of lesion, percentage of lumen occlusion, and presence of bleeding were recorded. Fluoroscopic visualization of the guide wire in the catheter tip assisted in demarcating the proximal and distal extent of the intraluminal tumor. 5Gy was prescribed to a distance of 1cm from the catheter and a computerized treatment planning system was used to optimize the dose distribution to the gross target volume with 1.5-2cm margins at the distal and proximal ends. Bronchoscopic and symptomatic response rates were assessed at the third HDR-EB and patients were seen in follow-up every 2 months. RESULTS: One hundred seventeen endobronchial treatments were delivered to 33 patients with primary carcinoma, and 8 patients with metastatic carcinoma. The median age was 69 (range = 36-94); 95% reported dyspnea; 71% cough and 22% hemoptysis. Seventy-two percent of patients reported resolution of their symptoms and 54% achieved a bronchoscopic response (at least 50% decrease in intraluminal obstruction). In a multivariate logistic model including stage, age, primary tumor type, and Karnofsky performance status (KPS) as predictors, only KPS was statistically associated with bronchoscopic response (OR = 1.1; 95%CI = 1.01-1.13) and palliation of symptoms (OR = 1.3; 95%CI = 1.05-1.59). The overall median survival was 5.2 months and was associated with bronchoscopic response (11 months in responders vs 4 in nonresponders) and symptom resolution (8 months in responders vs 1.5 in nonresponders). In a multivariate Cox survival model with stage, age, primary tumor type, and KPS as predictors, only KPS was significantly associated with survival (RR = 0.92;95%CI = 0.88-0.95). CONCLUSIONS: HDR-EB with concomitant EBRT is an effective treatment regimen for patients with both endobronchial and extrabronchial tumor. Patients with higher performance status are more likely to have resolution of disease and have longer median survival.