American Society for Radiation Oncology (ASTRO) and American College of Radiology (ACR) practice guideline for the performance of high-dose-rate brachytherapy

High-Dose-Rate (HDR) brachytherapy is a safe and efficacious treatment option for patients with a variety of different malignancies. Careful adherence to established standards has been shown to improve the likelihood of procedural success and reduce the incidence of treatment-related morbidity. A collaborative effort of the American College of Radiology (ACR) and American Society for Therapeutic Radiation Oncology (ASTRO) has produced a practice guideline for HDR brachytherapy. The guideline defines the qualifications and responsibilities of all the involved personnel, including the radiation oncologist, physicist and dosimetrists. Review of the leading indications for HDR brachytherapy in the management of gynecologic, thoracic, gastrointestinal, breast, urologic, head and neck, and soft tissue tumors is presented. Logistics with respect to the brachytherapy implant procedures and attention to radiation safety procedures and documentation are presented. Adherence to these practice guidelines can be part of ensuring quality and safety in a successful HDR brachytherapy program.     

A population-based study of cervix cancer: incidence, management and outcome in the Canadian province of Saskatchewan

Aims

To document the incidence, management and outcome of uterine cervix cancer in the Canadian province of Saskatchewan. To compare provincial results of low dose rate (LDR) and high dose rate (HDR) brachytherapy in this population.

Materials and methods

We carried out a retrospective population-based cohort study of all uterine cervix cancer cases in Saskatchewan diagnosed between 1985 and 2001. We used data from the provincial cancer registry for incident cases, the provincial death registry for vital status information and chart reviews for treatment and toxicity information.

Results

In total, 714 cases of uterine cervix cancer were identified. Stage distribution was IA 22.7%, IB 31.8%, II 19.1%, III 18.4%, IV 6.8%; 81.2% were squamous cell carcinoma, 13.4% adenocarcinoma, 1.5% adenosquamous, 0.9% small cell and 3.1% other. The annual crude incidence rate of uterine cervix cancer in Saskatchewan ranged from 6.5 to 12.3% between 1985 and 2001. The 5-year cause-specific survival rate ranged from 100% for stage IA1 to 22% for stage IV. One hundred and seven patients were treated with LDR and 37 with HDR with similar stage distribution. The 5-year cause-specific survival rate was 56% for HDR and 67% for LDR (P = 0.72). For 43 patients managed with external beam radiotherapy alone, outcome was poor for stage IIB to IIIB. The most common acute toxicities of radiation treatment were diarrhoea (60%) and abdominal cramps (12.5%). The common chronic toxicities were vaginal stenosis (5.5%) and small bowel obstruction (4%).

Conclusions

Our population-level outcomes are in keeping with published observed results and provide some of the first Canadian population-level data on HDR and LDR outcomes. We found no significant different in cause-specific survival between patients managed with HDR and LDR, although interpretation is limited by patient numbers. Our results for external beam radiotherapy alone emphasise the vital role brachytherapy plays in the management of cervical cancer.     

A phase IB clinical trial of 15 Gy HDR brachytherapy followed by hypofractionated/SBRT in the management of intermediate-risk prostate cancer

PurposeHigh dose-rate (HDR) brachytherapy is commonly administered as a boost to external beam radiation therapy (EBRT). Our purpose was to compare toxicity with increasingly hypofractionated EBRT in combination with a single 15 Gy HDR boost for men with intermediate-risk prostate cancer.Methods and MaterialsForty-two men were enrolled on this phase IB clinical trial to one of three EBRT dose cohorts: 10 fractions, seven fractions, or five fractions. Patients were followed prospectively for safety, efficacy, and health-related quality of life (Expanded Prostate Index Composite). Efficacy was assessed biochemically using the Phoenix definition.ResultsWith a median follow up of 36 months, the biochemical disease-free survival was 95.5%. One man developed metastatic disease at 5 years. There was no significant minimally important difference in EPIC PRO for either urinary, bowel, or sexual domains. There was one acute Grade 3 GI and GU toxicity, but no late Grade 3 GU or GI toxicities.ConclusionFifteen gray HDR brachytherapy followed by a five fraction SBRT approach results in high disease control rates and low toxicity similar to previously reported HDR protocols with significant improvement in patient convenience and resource savings. While mature results with longer follow up are awaited, this treatment approach may be considered a safe and effective option for men with intermediate-risk disease.     

Development,implementation, and associated challenges of a new HDR brachytherapy program

Developing any new radiation oncology program requires planning and analysis of the current state of the facility and its capacity to take on another program. Staff must consider a large number of factors to establish a feasible, safe, and sustainable program. We present a simple and generic outline that lays out the process for developing and implementing a new HDR brachytherapy program in any setting, but with particular emphasis on challenges associated with starting the program in a limited resource setting. The sections include feasibility of a program, starting cases, machine and equipment selection, and quality and safety.     

三维后装治疗模拟计划系统设计和验证研究

开发和验证基于CT图像的三维后装治疗模拟计划系统。用VC 开发以CT图像为基础的三维后装治疗模拟计划系统(3D-BSS),用JR1152-F型热释光剂量计(TLD,1mm×1mm×6mm)和仿真人体盆腔模型(CDP)验证该系统的准确性。实测剂量值与3D-BSS计算值符合较好,相对偏差在10%以内。3D-BSS准确可靠,用JR1152-F型TLD和仿真人体盆腔模型验证宫颈癌腔内后装治疗三维剂量分布具有可行性。     

Site‐specific transgenesis of the Drosophila melanogaster Y‐chromosome using CRISPR/Cas9

Despite the importance of Y‐chromosomes in evolution and sex determination, their heterochromatic, repeat‐rich nature makes them difficult to sequence (due, in part, to ambiguities in sequence alignment and assembly) and to genetically manipulate. Therefore, they generally remain poorly understood. For example, the Drosophila melanogaster Y‐chromosome, one of the most extensively studied Y‐chromosomes, is widely heterochromatic and composed mainly of highly repetitive sequences, with only a handful of expressed genes scattered throughout its length. Efforts to insert transgenes on this chromosome have thus far relied on either random insertion of transposons (sometimes harbouring ‘landing sites’ for subsequent integrations) with limited success or on chromosomal translocations, thereby limiting the types of Y‐chromosome‐related questions that could be explored. Here, we describe a versatile approach to site‐specifically insert transgenes on the Y‐chromosome in D. melanogaster via CRISPR/Cas9‐mediated homology‐directed repair. We demonstrate the ability to insert, and detect expression from, fluorescently marked transgenes at two specific locations on the Y‐chromosome, and we utilize these marked Y‐chromosomes to detect and quantify rare chromosomal nondisjunction effects. Finally, we discuss how this Y‐docking technique could be adapted to other insects to aid in the development of genetic control technologies for the management of insect disease vectors and pests.     

Optimization of planar high-dose-rate implants

Purpose: Brachytherapy has long been used to deliver localized radiation to the breast and other cancer sites. For interstitial implants, proper source positioning is critical in obtaining satisfactory dose distributions. The present work examines techniques for optimizing source guide placement in high-dose-rate (HDR) biplanar implants, and examines the effects of suboptimal catheter placement.

Methods and Materials: Control of individual dwell times in HDR implants allows a high degree of dose uniformity in planes parallel to the implant planes. Biplanar HDR implants can be considered optimized when the dose at the implant center is equal to the dose at the symmetric target boundaries. It is shown that this optimal dose uniformity is achieved when the interplanar separation is related to the target thickness T through the direct proportionality, s = T/√2. To quantify the significance of source positioning, the average dose and a related quantity, equivalent uniform dose (EUD), were calculated inside the treatment volume for two conditions of suboptimal catheter geometry. In one case, the interplanar spacing was varied from 1 cm up to the target thickness T, while a second study examined the effects of off-center placement of the implant planes.

Results: Both the average dose and EUD were minimized when the interplanar spacing satisfied the relationship s = T/ √2. EUD, however, was significantly smaller than the average dose, indicating a reduced relative cell killing in the high dose regions near the dwell points. It was also noted that in contrast to the average dose, the EUD is a relatively weak function of catheter misplacement, suggesting that the biological consequences of suboptimal implant geometry may be less significant than is indicated by the increase in average dose.

Conclusion: A concise formula can be used to determine the interplanar separation needed for optimal dose uniformity in Manchester-type implants. Deviations from optimal source geometry result in an increase in the average dose inside the treatment volume, but the weaker dependence of the EUD suggests that the surviving fraction of cells may not be not strongly affected by suboptimal source geometry.     

In vivo diode dosimetry vs. computerized tomography and digitally reconstructed radiographs for critical organ dose calculation in high-dose-rate brachytherapy of cervical cancer

Purpose

To investigate the correlation between the dose predicted by the treatment planning system using digitally reconstructed radiographs or three-dimensional (3D)-reconstructed CT images and the dose measured by semiconductor detectors, under clinical conditions of high-dose-rate brachytherapy of the cervix uteri.

Patients and methods

Thirty-two intracavitary brachytherapy applications were performed for 12 patients with cancer of the cervix uteri. The prescribed dose to Point A was 7 Gy. Dose was calculated for both International Commissioning on Radiation Units and Measurements (ICRU) bladder and rectal points based on digitally reconstructed radiographs and for 3D CT images-based volumetric calculation of the bladder and rectum. In vivo diode dosimetry was performed for the bladder and rectum.

Results

The ICRU reference point and the volumes of 1, 2, and 5 cm³ received 3.6 ± 0.9, 5.6 ± 2.0, 5.1 ± 1.7, 4.3 ± 1.4 and 5.0 ± 1.2, 5.3 ± 1.3, 4.9 ± 1.1, and 4.2 ± 0.9 Gy for the bladder and rectum, respectively. The ratio of the 1 cm³ and the ICRU reference point dose to the diode dose was 1.8 ± 0.7 and 1.2 ± 0.5 for the bladder and 1.9 ± 0.6 and 1.7 ± 0.5 for the rectum, respectively.

Conclusions

3D image-based dose calculation is the most accurate and reliable method to evaluate the dose given to critical organs. In vivo diode dosimetry is an important method of quality assurance, but clinical decisions should be made based on 3D-reconstructed CT image calculations.