Curiethérapie à l’institut Gustave-Roussy : applicateur moulé vaginal personnalisé : modification et amélioration techniques

Emerging technologies in brachytherapy

Brachytherapy is a mature treatment modality. The literature is abundant in terms of review articles and comprehensive books on the latest established as well as evolving clinical practices. The intent of this article is to part ways and look beyond the current state-of-the-art and review emerging technologies that are noteworthy and perhaps may drive the future innovations in the field. There are plenty of candidate topics that deserve a deeper look, of course, but with practical limits in this communicative platform, we explore four topics that perhaps is worthwhile to review in detail at this time. First, intensity modulated brachytherapy (IMBT) is reviewed. The IMBT takes advantage ofanisotropicradiation profile generated through intelligent high-density shielding designs incorporated onto sources and applicators such to achieve high quality plans. Second, emerging applications of 3D printing (i.e. additive manufacturing) in brachytherapy are reviewed. With the advent of 3D printing, interest in this technology in brachytherapy has been immense and translation swift due to their potential to tailor applicators and treatments customizable to each individual patient. This is followed by, in third, innovations in treatment planning concerning catheter placement and dwell times where new modelling approaches, solution algorithms, and technological advances are reviewed. And, fourth and lastly, applications of a new machine learning technique, called deep learning, which has the potential to improve and automate all aspects of brachytherapy workflow, are reviewed. We do not expect that all ideas and innovations reviewed in this article will ultimately reach clinic but, nonetheless, this review provides a decent glimpse of what is to come. It would be exciting to monitor as IMBT, 3D printing, novel optimization algorithms, and deep learning technologies evolve over time and translate into pilot testing and sensibly phased clinical trials, and ultimately make a difference for cancer patients. Today's fancy is tomorrow's reality. The future is bright for brachytherapy.

Hypnosedation for endocavitary uterovaginal applications: A pilot study

PURPOSE

Implantations for uterovaginal brachytherapy are usually performed under general or spinal anesthesia, which are not without risk. As it is a rather short procedure and since postoperative pain is minimal, hypnosedation was proposed to selected patients requiring endocavitary applications as part of their routine treatment.

METHODS AND MATERIALS

Consecutive patients requiring intracavitary uterovaginal brachytherapy from January to October 2019 were included if they accepted the procedure. A premedication was systematically administered. Hypnosedation was based on an Ericksonian technique. The procedure was immediately interrupted if the patient requested it, in cases of extreme anxiety or pain. Procedure was in that case rescheduled with a "classical" anesthesia technique.

RESULTS

A total of 20 patients were included. Four patients had to be converted toward a general anesthesia: one because of a fibroma on the probe's way and three young patients with a very anteverted/retroverted uterus that was painful at every mobilization. Mean and maximum pain scores during implant were 2.9/10 and 5.1/10, respectively. The most painful maneuver was cervical dilation for 45% of the patients, followed by mold insertion in 40% of cases. About 85% of the patients declared that hypnosis helped them relax; 90% of the patients would recommend the technique. No procedure-related complication occurred.

CONCLUSION

With a 70% success rate (correct implant with mean pain and anxiety scores < 5), one can conclude that uterovaginal brachytherapy implantation under hypnosedation is feasible and received a high satisfaction rate from the patients. This technique may reduce overall treatment time in a context of difficult access to the OR and to anesthesiologists, while reducing anesthetic drugs resort and postoperative nausea.

Outcomes of pre-operative brachytherapy followed by hysterectomy for early cervical cancer

OBJECTIVE

The standard of care for early cervical cancer is radical hysterectomy; however, consideration of pre-operative brachytherapy has been explored. We report our experience using pre-operative brachytherapy plus Wertheim-type hysterectomy to treat early stage cervical cancer.

METHODS

This single-center study evaluated consecutive patients with histologically proven node-negative early stage cervical cancer (International Federation of Gynecology and Obstetrics 2009 stage IB1-IIB) that was treated using pre-operative brachytherapy and hysterectomy. Pre-brachytherapy staging was performed using magnetic resonance imaging (MRI) and pelvic lymph node assessment was performed using lymphadenectomy. The tumor and cervical tissues were treated using brachytherapy (total dose 60 Gy) followed by Wertheim-type hysterectomy. The study included patients from January 2000 to December 2013.

RESULTS

A total of 80 patients completed a median follow-up of 6.7 years (range 5.4-8.5). The surgical specimens revealed a pathological complete response for 61 patients (76%). Patients with incomplete responses generally had less than 1 cm residual tumor at the cervix, and only one patient had lymphovascular space involvement. The estimated 5-year rates were 88% for overall survival (95% CI 78% to 94%) and 82% for disease-free survival (95% CI 71% to 89%). Toxicities were generally mild-to-moderate, including 26 cases (33%) of grade 2 late toxicity and 10 cases (13%) of grade 3 late toxicity. Univariate analyses revealed that poor disease-free survival was associated with overweight status (≥25 kg/m², HR 3.05, 95% CI 1.20 to 7.76, p=0.019) and MRI tumor size >3 cm (HR 3.05, 95% CI 1.23 to 7.51, p=0.016).

CONCLUSIONS

Pre-operative brachytherapy followed by Wertheim-type hysterectomy may be safe and effective for early stage cervical cancer, although poorer outcomes were associated with overweight status and MRI tumor size >3 cm.

The design of an individualized cylindrical vaginal applicator with oblique guide holes using 3D modeling and printing technologies

High-dose-rate brachytherapy for cervical cancer after subtotal hysterectomy using standardized applicators cannot achieve a good absorbed-dose coverage of the target volume in special tumor morphologies and topographies due to the steep dose gradient. The aim of this pictorial essay is to present an individualized cylindrical vaginal applicator with oblique guide holes using 3D modeling and printing technologies used at the China-Japan Union Hospital of Jilin University for cervical cancer patients. We use images to describe the steps of this method.

Characterisation of radiological properties of a brachytherapy moulding material

The use of a non-water-equivalent personalised mould for gynaecological brachytherapy treatments can result in a substantial dose reduction at the treatment site, compared to calculated dose, in lieu of a dose calculation algorithm capable of modelling non-water-equivalent materials. This study describes the characterisation of the radiological properties of a brachytherapy applicator moulding material. Simple line source correction factors for an ¹⁹²Ir source are obtained through Monte Carlo simulations and verified by film measurements. The dwell position corrections are used to estimate aggregate correction factors for dose deliveries that involve multiple dwell positions, in terms of treatment length, applicator radii and depth of reference dose. For the Fricotan moulding material used locally, the dose reductions varied from 1% for an applicator radius of 0.5 cm to > 4% for radii exceeding 2 cm. The method described in this paper could be used to develop correction factors for other non-water-equivalent moulding materials, in a TG-43UI dose calculation environment.

Image-Based Brachytherapy for the Treatment of Cervical Cancer

Cervical cancer is a disease that requires considerable multidisciplinary coordination of care and labor in order to maximize tumor control and survival while minimizing treatment-related toxicity. As with external beam radiation therapy, the use of advanced imaging and 3-dimensional treatment planning has generated a paradigm shift in the delivery of brachytherapy for the treatment of cervical cancer. The use of image-based brachytherapy, most commonly with magnetic resonance imaging (MRI), requires additional attention and effort by the treating physician to prescribe dose to the proper volume and account for adjacent organs at risk. This represents a dramatic change from the classic Manchester approach of orthogonal radiographic images and prescribing dose to point A. We reviewed the history and currently evolving data and recommendations for the clinical use of image-based brachytherapy with an emphasis on MRI-based brachytherapy.

Evaluation of PC-ISO for customized, 3D Printed, gynecologic 192-Ir HDR brachytherapy applicators

The purpose of this study was to evaluate the radiation attenuation properties of PC-ISO, a commercially available, biocompatible, sterilizable 3D printing material, and its suitability for customized, single-use gynecologic (GYN) brachytherapy applicators that have the potential for accurate guiding of seeds through linear and curved internal channels. A custom radiochromic film dosimetry apparatus was 3D-printed in PC-ISO with a single catheter channel and a slit to hold a film segment. The apparatus was designed specifically to test geometry pertinent for use of this material in a clinical setting. A brachytherapy dose plan was computed to deliver a cylindrical dose distribution to the film. The dose plan used an 192Ir source and was normalized to 1500 cGy at 1 cm from the channel. The material was evaluated by comparing the film exposure to an identical test done in water. The Hounsfield unit (HU) distributions were computed from a CT scan of the apparatus and compared to the HU distribution of water and the HU distribution of a commercial GYN cylinder applicator. The dose depth curve of PC-ISO as measured by the radiochromic film was within 1% of water between 1 cm and 6 cm from the channel. The mean HU was -10 for PC-ISO and -1 for water. As expected, the honeycombed structure of the PC-ISO 3D printing process created a moderate spread of HU values, but the mean was comparable to water. PC-ISO is sufficiently water-equivalent to be compatible with our HDR brachytherapy planning system and clinical workflow and, therefore, it is suitable for creating custom GYN brachytherapy applicators. Our current clinical practice includes the use of custom GYN applicators made of commercially available PC-ISO when doing so can improve the patient's treatment. 

A unique approach to high-dose-rate vaginal mold brachytherapy of gynecologic malignancies

PURPOSE

Patients with cervical and vaginal cancer sometimes have a less straightforward approach for choice of brachytherapy treatment owing to the tumor's location and clinical presentation. The staff at Royal Brisbane & Women's Hospital in Queensland, Australia, is trying to solve this problem by the use of an old technique in a new approach called vaginal molds. With a patient-specific vaginal mold, the appearance of the applicator and the dose distribution can be customized to provide an optimal treatment for each patient.

METHODS AND MATERIALS

The technique used at the Royal Brisbane & Women's Hospital uses a flexible two-part putty, moulded to the shape of the vagina, in which standard catheters (flexible implant tubes) are incorporated, in a pattern designed to permit a dose distribution more conformal to the target volume.

RESULTS

The presented technique is efficient and improves the accuracy of a homogeneous target cover and sparing of organs at risk for vaginal mold brachytherapy treatments at our institution.

CONCLUSION

This technique offers a customizable option when traditional cylindrical- or dome-type applicators cannot be used, or provide inadequate dose coverage. Molds to match the patient anatomy can be created quickly, while allowing flexibility in positioning of catheters to achieve the desired dose distribution.

Adaptive 3D image-guided brachytherapy: a strong argument in the debate on systematic radical hysterectomy for locally advanced cervical cancer

PURPOSE

To evaluate the outcomes of patients with locally advanced cervical cancer treated with three-dimensional image-guided brachytherapy (IGABT) after concomitant chemoradiation (CCRT).

MATERIALS AND METHODS

Data from patients treated with CCRT followed by magnetic resonance imaging-guided or computed tomography-guided pulsed-dose-rate brachytherapy, performed according to the Groupe Européen de Curiethérapie-European Society for Radiotherapy and Oncology guidelines, were reviewed. At first, stage I or II patients systematically underwent radical hysterectomy or were offered a randomized study evaluating hysterectomy. Then, hysterectomy was limited to salvage treatment.

RESULTS

Of 163 patients identified, 27% had stage IB, 57% had stage II, 12% had stage III, and 3% had stage IVA disease. The mean dose delivered (in 2-Gy dose equivalents) to 90% of the high-risk clinical target volume was 78.1 ± 9.6 Gy, whereas the doses delivered to organs at risk were maintained under the usual thresholds. Sixty-one patients underwent a hysterectomy. Macroscopic residual disease was found in 13 cases. With a median follow-up of 36 months (range, 5-79 months), 45 patients had relapsed. The 3-year overall survival rate was 76%. Local and pelvic control rates were 92% and 86%, respectively. According to the Common Toxicity Criteria 3.0, 7.4% of patients experienced late grade 3 or 4 toxicity. Most of those had undergone postradiation radical surgery (2.9% vs. 14.8; p = .005).

CONCLUSION

IGABT combined with CCRT provides excellent locoregional control rates with low treatment-related morbidity, justifying the elimination of hysterectomy in the absence of obvious residual disease. Distant metastasis remains an important first relapse and may warrant more aggressive systemic treatment.

Adjuvant intravaginal brachytherapy for uterus didelphys with synchronous endometrial adenocarcinomas and unfavourable vaginal topography

► We describe a case of uterus didelphys with synchronous endometrial cancers. ► Unfavorable post-operative disturbance of the vaginal vault topography was present. ► Hence the Institut Gustave-Roussy "moulage" IVBT technique was utilised. ► This customised technique achieved excellent mould-to-mucosa conformance.

[Implementation of GEC-ESTRO recommendations on 3-D based image brachytherapy]

Even if the prognosis of patients with cervical cancer has been dramatically improved with concomitant chemoradiation, brachytherapy still plays fundamental role in the therapeutic approach of patients with Figo stage I-IV cervical carcinoma. The development of imaging with three-dimensional dosimetry has contributed to the improvement in target and organs at risk knowledge. In 2005 and 2006, GEC-ESTRO recommendations on 3-D based image brachytherapy have defined the different volumes of interest. These recommendations have been validated with intercomparison delineation studies. Data on dose to normal tissues are better known with dose volume-histograms analysis. Dose limits to the bladder are high in the range of 90 Gy to the 2 cm3 while 2 cm3 limits to the rectum do not differ from ICRU point. The sigmoid is currently under study as this organ was not extensively studied before the era of imaging. Doses to the tumour (HR-CTV or IR-CTV) are not clearly stated and will likely depend on tumour extension.