Intraoperative HDR Brachytherapy: Present and Future

Radiotherapy is one of the most effective modalities in cancer treatment, and can be applied either by external beam radiotherapy or by brachytherapy. Brachytherapy is a treatment modality in which tumors are irradiated by positioning radioactive sources very close to or in the tumor volume. The use of (fractionated) HDR and PDR brachytherapy has increased dramatically. In chapter 2 the techniques and results of fractionated HDR and PDR brachytherapy for head and neck cancer are presented. HDR/PDR brachytherapy is usually performed with single stepping source afterloaders, containing a small Iridium-192 source, enabling optimization of the dose distribution by optimization of the dwell times over all dwell positions in the implant. In chapter 3 the effects of geometric optimization on the dose distribution of interstitial volume implants have been studied in terms of the irradia¬ted volume, the dose uniformity, and the choice of the reference dose. The results of anatomy based inverse planning in HDR prostate implants are evaluated in chapter 4. An Integrated Brachytherapy Unit (IBU), i.e. a shielded operating room with an HDR afterloader and a dedicated brachytherapy localiser, connected to a treatment planning computer, was established at the Erasmus MC – Daniel Den Hoed Cancer Center. This set-up enables integration of the entire brachy¬therapy procedure, i.e. implantation, implant reconstruction, dose planning and delivery in a single session. In chapter 5 the reconstruction accuracy of this dedicated localiser has been evaluated by simulations and by measurements using phantoms representing clinical relevant implant geometries. When converting to on-line planning by importing the fluoroscopy images directly in the planning computer the image distortions present in fluoroscopy images should be eliminated. In chapter 6, the accuracy of on-line planning in the IBU using dedicated image distortion correction algorithms has been evaluated. The availability of an HDR afterloader in the IBU enables the use of intraoperative brachytherapy (IOBT). IOBT is applied using a 5 mm thick flexible intraoperative template (FIT). To reduce the procedure time, treatment planning is performed using standard plans, that neglect the curvature of the FIT. In chapter 7 we have calculated the individual treatment plan, based on the real geometry of the FIT, and the dose at clips placed during surgery, of 32 patients with locally advanced rectal tumors treated this way. In chapter 8 the technique and results, in terms of local failure and survival, of IOBT for patients with locally advanced or recurrent rectal cancer are discussed. A taskgroup on quality assurance (QA) of brachytherapy systems of the Netherlands Commission on Radiation Dosimetry was established to develop nation wide accepted guidelines for QA in brachytherapy. The taskgroup investigated the accuracy of brachytherapy treatments in 33 radiotherapy institutions in The Netherlands and Belgium, by determining the accuracy of implant reconstruction and dose delivery (chapter 9). In chapter 10 the practice of brachytherapy QA in The Netherlands and Belgium was evaluated and compared with international recommendations. The determination of the reference air kerma rate for Iridium-192 sources and the related uncertainty are discussed in chapter 11. In chapter 12 the presented set-up for HDR (intraoperative) brachytherapy is discussed in some more detail and future perspectives are presented

Determination of the accuracy of implant reconstruction and dose delivery in brachytherapy in The Netherlands and Belgium

Purpose: To gain insight into the accuracy of brachytherapy treatments, the accuracy of implant reconstruction and dose delivery was investigated in 33 radiotherapy institutions in The Netherlands and Belgium. Materials and methods: The accuracy of the implant reconstruction method was determined using a cubic phantom containing 25 spheres at well-known positions. Reconstruction measurements were obtained on 41 brachytherapy localizers, 33 of which were simulators. The reconstructed distances between the spheres were compared with the true distances. The accuracy of the dose delivery was determined for high dose rate (HDR), pulsed dose rate (PDR) and low dose rate (LDR) afterloading systems using a polymethyl methacrylate cylindrical phantom containing a NE 2571 ionization chamber in its centre. The institutions were asked to deliver a prescribed dose at the centre of the phantom. The measured dose was compared with the prescribed dose. Results: The average reconstruction accuracy was -0.07 mm (±0.4 mm, 1 SD) for 41 localizers. The average deviation of the measured dose from the prescribed dose was +0.9% (±1.3%, 1 SD) for 21 HDR afterloading systems, +1.0% (±2.3%, 1 SD) for 12 PDR afterloaders, and +1.8% (±2.5%, 1 SD) for 15 LDR afterloaders. Conclusions: This comparison showed a good accuracy of brachytherapy implant reconstruction and dose delivery in The Netherlands and Belgium

HDR monotherapy for prostate cancer: A simulation study to determine the effect of catheter displacement on target coverage and normal tissue irradiation

Purpose: The aim of this study was to systematically analyse the effect of catheter displacements both on target coverage and normal tissue irradiation in fractionated high dose rate (HDR) prostate brachytherapy, using a simulation study, and to define tolerances for catheter displacement ensuring that both target coverage and normal tissue doses remain clinically acceptable. Besides the effect of total implant displacement, also displacements of catheters belonging to selected template rows only were evaluated in terms of target coverage and normal tissue dose, in order to analyse the change in dose distribution as a function of catheter dwell weight and catheter location. Material and methods: Five representative implant geometries, with 17 catheters each, were selected. The clinical treatment plan was compared to treatment plans in which an entire implant displacement in caudal direction over 3, 5, 7 and 10 mm was simulated. Besides, treatment plans were simulated considering a displacement of either the central, most ventral or most dorsal catheter rows only, over 5 mm caudally. Results: Due to displacement of the entire implant the target coverage drops below the tolerance of 93% for all displacements studied. The effect of displacement of the entire implant on organs at risk strongly depended on the patient anatomy; e.g., for 80% of the implant geometries the V80 of the rectum exceeded its tolerance for all displacements. The effect of displacement of catheters belonging to selected template rows depended strongly on the relative weight of each catheter row when considering the target coverage and on its location when considering the dose in the organs at risk. Conclusion: This study supports the need for a check of the catheter locations before each fraction and correction of deviations of the catheter position exceeding 3 mm

High-dose-rate brachytherapy and external-beam radiotherapy for hormone-naïve low- and intermediate-risk prostate cancer: A 7-year experience

Purpose: To report clinical outcomes and early and late complications in 264 hormone-naïve patients with low- and intermediate-risk prostate cancer treated with high-dose-rate brachytherapy (HDR-BT) in combination with external-beam radiotherapy (EBRT). Methods and Materials: Between February 2000 and July 2007, 264 patients underwent HDR-BT in combination with EBRT as a treatment for their low- to intermediate-risk prostate cancer. The HDR-BT was performed using ultrasound-based implantation. The total HDR-BT dose was 18 Gy in 3 fractions within 24 h, with a 6-h minimum interval. The EBRT started 2 weeks after HDR-BT and was delivered in 25 fractions of 1.8 Gy to 45 Gy within 5 weeks. Results: After a mean follow-up of 74.5 months, 4 patients (1.5%) showed prostate-specific antigen progression according to the American Society for Radiation Oncology definition and 8 patients (3%) according to the Phoenix definition. A biopsy-proven local recurrence was registered in 1 patient (0.4%), and clinical progression (bone metastases) was documented in 2 patients (0.7%). Seven-year actuarial freedom from biochemical failure was 97%, and 7-year disease-specific survival and overall survival were 100% and 91%, respectively. Toxicities were comparable to other series. Conclusions: Treatment with interstitial HDR-BT plus EBRT shows a low incidence of late complications and a favorable oncologic outcome after 7 years follow-up

Toxicity and quality of life after high-dose-rate brachytherapy as monotherapy for low- and intermediate-risk prostate cancer

Background and purpose The use of HDR brachytherapy (HDR-BT) as monotherapy for prostate cancer (PC) is increasing worldwide with good tumour control rates and acceptable toxicity. We report our results on toxicity and quality of life (QoL) after HDR-BT monotherapy for PC patients. Materials and methods 166 low- and intermediate-risk localized PC patients were treated with HDR-BT to a total dose of 38 Gy in four fractions. Genitourinary (GU) and gastrointestinal (GI) toxicities were prospectively assessed using EORTC-RTOG questionnaires and physicians charts. QoL was evaluated using EORTC QLQ-PR25 questionnaires. Results Three months after treatment, acute GU and GI toxicities were reported in 10.8% and 7.2%. Acute toxicity resolved within two months in the majority of patients (61%). Late grade ≥2 GU and GI toxicity were reported in 19.7% and 3.3% of patients 12 months after HDR-BT. Mean QLQ-PR25 scores showed clinically relevant changes from baseline for urinary symptoms and sexual functioning. With a mean follow-up of 35 months, biochemical failure was observed in 2.4%. Overall survival at 60 months was 93.6% and cancer-specific survival was 100%. Conclusions HDR-BT monotherapy for localized PC showed excellent clinical outcome and acceptable acute and late toxicity. Urinary symptoms and sexual function QoL decreased after treatment