Experiences with a new high-dose-rate brachytherapy (HDR-BT) boost technique for T3b prostate cancer.

PURPOSE: Experiences with a new high-dose-rate brachytherapy (HDR-BT) boost technique in 41 patients with stage T3b prostate cancer are presented. PATIENTS AND METHODS: The patients received 18 Gy of HDR-BT (9 Gy on days 1 + 8) plus 50.4 Gy of EBRT. 20 patients (group A) had BT applicators placed into the prostate alone resulting in 18 Gy to prostate and 0 Gy (tip) to 12 Gy (base) to seminal vesicles (SV). The cumulative EQD2 (equivalent dose in 2-Gy fractions, alpha/beta 1.5 Gy) to the SV was 47.5-73.3 Gy. 21 patients (group B) had BT applicators placed into both prostate and SV resulting in 18 Gy to prostate and to > 80% (but not 100%) of the SV (cumulative EQD2 81.5-101.5 Gy). Both groups were compared for acute and late toxicity and for biochemical relapse-free survival (bRFS). RESULTS: The 3-year bRFS was 57% for group A and 79% for group B patients (p = 0.29). A grade 3 acute toxicity (CTC 2.0) was not observed. Grade 2 acute toxicity (proctitis, cystitis, skin toxicity) was comparable in both groups. A grade 3 late toxicity did not occur. Impotence rates were 35% in group A and 24% in group B, respectively (p = 0.73). CONCLUSION: The new HDR-BT technique (group B) was associated only with minor acute and late toxicity and appears to result in better bRFS than the conventional HDR-BT technique (group A). The results must be confirmed in a prospective trial.

[Investigations of beta-dosimetry at two different sources for the cardiovascular brachytherapy]. / Untersuchungen zur beta-Dosimetrie an zwei unterschiedlichen Quellen für die kardiovaskuläre Brachytherapie.

The intracoronary brachytherapy is used at the Hamburg University Hospital as a method to treat in-stent restenosis. Two different radiochromic film types were applied to obtain dosimetric information of the beta-sources used (32P and 90Sr/90Y). First, these films were analyzed for their suitability for dosimetry. Within the investigated dose range (MD-55-2: 0 to 33 Gy, HD-810: 0 to 105 Gy), both films showed a linear behavior between the dose and the optical density (OD). Because radiochromic films are subject to time-based changes in OD, a method for colour stabilization was investigated (RCS-method). This method allowed to greatly shorten the time between irradiation and evaluation from 24 hours (time necessary for the film to reach a quasi-stable status) to 2.5 hours. Colour-stabilized films can also be stored for a long time and reanalyzed with almost the same results. Within the limits of the measurements error, both film types showed an energy independent response. Within the dose profiles, analyses of the two source types resulted in differences of 13.5% (32P) and 21% (90Sr/90Y). These inhomogenities are consistent with the fabrication tolerances given by the manufactures.

Emergency localization of radioactive seeds lost during intracoronary brachytherapy.

Recently, it has been reported that brachytherapy catheters ruptured in vivo. Localization of lost beta-radiation-emitting seeds is a problem because no appropriate technique is available that is rapid and precise. We developed a technique to localize beta-emitting seeds utilizing the effect that beta-radiation induces bremsstrahlung. The loss of a single radioactive source was simulated in an Alderson Phantom representing a human body. The beta-induced bremsstrahlung could be detected selectively by a gamma-camera. The position of the radioactive seed could be located within 5 min with an accuracy of +/- 0.5 cm. The result of this study suggests that in an emergency case of loss of a brachytherapy source, a commercially available gamma-camera can be a valuable tool to detect lost beta-radiation-emitting seeds rapidly and precisely. In addition, the technique minimizes the patient's as well as the surgeon's exposure to radiation and reduces the extent of surgical trauma.