Comparison of measurements of the uterus and cervix obtained by magnetic resonance and transabdominal ultrasound imaging to identify the brachytherapy target in patients with cervix cancer

High-Dose-Rate Three-Dimensional Image-Guided Adaptive Brachytherapy (3D IGABT) for Locally Advanced Cervical Cancer (LACC): A Narrative Review on Imaging Modality and Clinical Evidence

Background: Brachytherapy (BT) is a critical component of radiotherapy for locally advanced cervical cancer (LACC), and it has rapidly developed in recent decades. Since the advent of three-dimensional image-guided adaptive brachytherapy (3D-IGABT), magnetic resonance imaging (MRI) has emerged as the primary modality for image guidance. Meanwhile, other imaging modalities, such as computed tomography, 18F-fluorodeoxyglucose positron emission tomography, ultrasound, and their combinations have also been widely studied. Materials and methods: We reviewed studies on different imaging modalities utilized for target delineation and planning. Emerging techniques in IGABT like real-time image guidance and 3D printing were also included. We summarized research on their feasibility and concentrated on their clinical outcomes. Results: MRI-guided BT was the gold standard, and CT-guided BT was the most widely applied. Other modalities have shown feasibility and promising efficacy in dosimetry studies and preliminary outcomes. The longer-term clinical outcomes associated with these approaches require further elucidation. Conclusions: As 3D-IGABT was validated by promising clinical outcomes, the future of BT for LACC is expected to progress toward the refinement of more effective image-guided procedures. Moreover, achieving operational consensus and driving technological advancements to mitigate the inherent limitations associated with different imaging modes remain essential.

Application of three-dimensional multi-imaging combination in brachytherapy of cervical cancer

BACKGROUND

Three-dimensional (3D) imaging has an important role in brachytherapy and the treatment of cervical cancer. The main imaging methods used in the cervical cancer brachytherapy include magnetic resonance imaging (MRI), computer tomography (CT), ultrasound (US), and positron emission tomography (PET). However, single-imaging methods have certain limitations compared to multi-imaging. The application of multi-imaging can make up for the shortcomings and provide a more suitable imaging selection for brachytherapy.

PURPOSE

This review details the situation and scope of existing multi-imaging combination methods in cervical cancer brachytherapy and provides a reference for medical institutions.

MATERIALS AND METHODS

Searched the literature related to application of three-dimensional multi-imaging combination in brachytherapy of cervical cancer in PubMed/Medline and Web of Science electronic databases. Summarized the existing combined imaging methods and the application of each method in cervical cancer brachytherapy.

CONCLUSION

The current imaging combination methods mainly include MRI/CT, US/CT, MRI/US, and MRI/PET. The combination of two imaging tools can be used for applicator implantation guidance, applicator reconstruction, target and organs at risk (OAR) contouring, dose optimization, prognosis evaluation, etc., which provides a more suitable imaging choice for brachytherapy.

Galalae R. Ultrasound-Guided Brachytherapy for Cervical Cancer - A Tool for Quality Improvement in Brachytherapy?

Nowadays, brachytherapy is one of the major components to treat inoperable cervical cancer. Brachytherapy yields a higher dose to the target (cervix) while sparing normal tissues. Developments of brachytherapy stepped forward in the previous decade by image-guided brachytherapy (IGBT) turning brachytherapy from point-based planning to volume-based planning and IGBT improves the treatment quality for cervical cancer. Magnetic resonance imaging (MRI) or computed tomography (CT) is utilized in brachytherapy and showed promising results internationally. However, in a limited-resource area, the implementation of IGABT is difficult due to many causes (manpower, equipment, or budgets). To improve the quality in limited resources, ultrasound is introduced. The utilization of ultrasound in brachytherapy practice is to prevent uterine perforation during application. With present data, measurement by ultrasound showed the correlation to MRI measurement in uterine dimensions. With these aspects, there are many researches using ultrasound to improve the quality of treatment in brachytherapy, for example, to guide contouring on CT or to support brachytherapy planning. The use of ultrasound improves the quality of brachytherapy in comparison to conventional planning and supports the improvement in brachytherapy for cervical cancer.

Contemporary image-guided cervical cancer brachytherapy: Consensus imaging recommendations from the Society of Abdominal Radiology and the American Brachytherapy Society

PURPOSE

To present recommendations for the use of imaging for evaluation and procedural guidance of brachytherapy for cervical cancer patients.

METHODS

An expert panel comprised of members of the Society of Abdominal Radiology Uterine and Ovarian Cancer Disease Focused Panel and the American Brachytherapy Society jointly assessed the existing literature and provide data-driven guidance on imaging protocol development, interpretation, and reporting.

RESULTS

Image-guidance during applicator implantation reduces rates of uterine perforation by the tandem. Postimplant images may be acquired with radiography, computed tomography (CT), or magnetic resonance imaging (MRI), and CT or MRI are preferred due to a decrease in severe complications. Pre-brachytherapy T2-weighted MRI may be used as a reference for contouring the high-risk clinical target volume (HR-CTV) when CT is used for treatment planning. Reference CT and MRI protocols are provided for reference.

CONCLUSIONS

Image-guided brachytherapy in locally advanced cervical cancer is essential for optimal patient management. Various imaging modalities, including orthogonal radiographs, ultrasound, computed tomography, and magnetic resonance imaging, remain integral to the successful execution of image-guided brachytherapy.

Ultrasound-guided Brachytherapy for Cervix Cancer

Radiotherapy and brachytherapy are the definitive treatments for locally advanced cervix cancer. The use of soft-tissue imaging, particularly magnetic resonance imaging, has enhanced their effectiveness and improved clinical outcomes. However, the use of magnetic resonance imaging is largely restricted to well-resourced centres in both the first and developing world and remains elusive to many less advantaged centres, particularly those in areas with a high burden of cervix cancer. Ultrasound is an accessible, affordable and accurate imaging modality that can be used throughout the brachytherapy procedure. Ultrasound is primarily used to ensure safe insertion of the applicator but can also be used to guide planning. The methods used to utilise ultrasound images for planning are described. Ultrasound is particularly useful as a verification aid to confirm applicator placement after patients are moved and transferred around the radiotherapy department. It can also be used to verify the dimensions of treatment volumes over the course of brachytherapy. There is a crucial unmet need for an accessible economical soft-tissue imaging modality in cervical brachytherapy. Ultrasound has the potential to meet this need.

Application of transrectal ultrasound in guiding interstitial brachytherapy for advanced cervical cancer

Purpose

To investigate the role of transrectal ultrasound guidance in interstitial brachytherapy for cervical cancer.

Material and methods

Forty-eight patients who underwent interstitial brachytherapy treatment for cervical cancer between January 2017 and January 2018 were enrolled in the study. The distances between each inserted needle and the lesion were measured at seven sites by ultrasound (D1-D7) and compared to the corresponding distances (M1-M7) when visualised with nuclear magnetic resonance imaging (MRI). Measurements were paired on the basis of the observation sites, e.g. D1 and M1, D2 and M2. The statistical differences, intraclass correlation coefficients (ICCs), and linear relationships for the paired measurements were calculated.

Results

No significant differences were found between the paired M and D measurements, with all ICCs showing high levels of concordance (0.81-0.93).

Conclusions

Transrectal ultrasound showed strong agreement with MRI results in determining the position of the inserted needles. Transrectal ultrasound is a useful tool for guided interstitial brachytherapy and is appropriate for widespread use in the treatment of locally advanced cervical cancer.

Clinical Application of Ultrasound Guidance for Parametrial Treatment of Advanced Cervical Cancer

OBJECTIVES

To evaluate the accuracy of ultrasound (US) in determining the positions of parametrial implants by comparing US with magnetic resonance imaging (MRI) for advanced cervical cancer.

METHODS

Patients undergoing brachytherapy with parametrial implantation for cervical cancer from February 2017 to February 2019 were involved in the study. The transverse section of the cervix (surface S₁ ) and the transverse section 1 cm above the external cervix (surface S₂ ) were selected from MRI and US images as the observation planes. In the MRI observation plane, the distances between the uterine titanium needles and the uterine tube/implanter were set as M₁ to M₄ ; in the US observation plane, the distances between the uterine titanium needles and the uterine tube/implanter were set as D₁ to D₄ . The differences and consistency in M and D of each group were then compared.

RESULTS

There were no significant differences between M and D in each group (P = .058; P = .821; P = .870; and P = .936, respectively). The intraclass correlation coefficients of M and D in each group were 0.970, 0.968, 0.952, and 0.956. A regression analysis showed that the relationships between M and D in each group were as follows: M₁ = 0.9449D₁  + 0.1812; M₂ = 0.9463D₂  + 0.0965; M₃ = 0.9176D₃  + 0.1233; and M₄ = 0.9253D₄  + 0.1224.

CONCLUSIONS

In parametrial brachytherapy for cervical cancer, US can accurately determine the positions of parametrial implantation needles, which is already applicable on MRI, and can provide assistance in parametrial brachytherapy for advanced cervical cancer.

Prospective intra/inter-observer evaluation of pre-brachytherapy cervical cancer tumor width measured in TRUS and MR imaging

BACKGROUND

Ultrasound (US) imaging has been proved as an excellent diagnostic tool in gynecology and, due to its wide availability and limited cost, is under intense investigation as base for dose adaptation in cervical cancer brachytherapy. Purpose of this work is to test inter/intra-observer uncertainties between magnetic resonance (MR) and trans-rectal ultrasound (TRUS) imaging in defining maximum tumor width before first brachytherapy (BT) application in a prospective cohort of cervical cancer patients undergoing image-guided adaptive brachytherapy (IGABT).

METHODS

One hundred ten consecutive cervical cancer patients treated between 2013 and 2016 were included. Before the first BT implant patients underwent MR and TRUS scan with no applicator in place. Images were independently analyzed by three examiners, blinded to the other's results. With clinical information at hand, maximum tumor width was measured on preBT TRUS and MR. Quantitative agreement analysis was undertaken. Intra-class correlation coefficient (ICC), Passing-Bablok and Bland Altman plots were used to evaluate the intra/inter-observers measurement agreement.

RESULTS

Average difference between tumor width measured on MR (HRCTV_MR) and TRUS (HRCTV_TRUS) was 1.3 ± 3.2 mm (p <  0.001); 1.1 ± 4.6 mm (p = 0.01) and 0.7 ± 3 mm (p = 0.01). The error was less than 3 mm in 79, 82 and 80% of the measurements for the three observers, respectively. Intra-observer ICC was 0.96 (CI95% 0.94-0.97), 0.93 (CI95% 0.9-0.95) and 0.96 (CI95% 0.95-0.98) respectively. Inter-observer ICC for HRCTV_MR width measures was 0.92 (CI95% 0.89-0.94) with no difference among FIGO stages. Inter-observer ICC for HRCTV_TRUS was 0.86 (CI95% 0.81-0.9). For FIGO stage I and II tumors, ICC HRCTV_TRUS values were comparable to respective HRCTV_MR ICC values. For larger tumors HRCTV_TRUS inter-observer ICC values were lower than respective HRCTV_MR although remaining acceptable.

CONCLUSIONS

Our results suggest that TRUS is equivalent to MR in assessing preBT tumor maximum width in cervical cancer FIGO stage I/II. In more advanced stages TRUS seems to be slightly inferior to MR although maintaining a good agreement to gold standard imaging.

Indian Brachytherapy Society Guidelines for radiotherapeutic management of cervical cancer with special emphasis on high-dose-rate brachytherapy

Brachytherapy (BT) for locally advanced cervical cancer is vital for optimal outcomes. There is heterogeneity in brachytherapy treatment practice for cervical cancer across India. In an attempt to standardize various processes involved in cervical cancer brachytherapy, the expert members of the Indian Brachytherapy Society (IBS) developed a document related to radiation therapy treatment of cervical cancer with special emphasis on brachytherapy. The guidelines are based on high quality clinical evidence, expert opinion and consensus wherever evidence was lacking. The document provides a guide for external beam radiation and details of all the processes involved in high-dose-rate (HDR) brachytherapy including patient selection, preparation, principles and technique of BT applications, target and normal tissue definition, dose prescriptions, BT planning, reporting parameters, common complications of BT and their management, scope for research, etc. In summary, we present here practical tips and tricks, recording and reporting of cervical cancer brachytherapy, which can be implemented in various clinical environments and forms the basis of this report.

Review of strategies for MRI based reconstruction of endocavitary and interstitial applicators in brachytherapy of cervical cancer

Brachytherapy plays an essential role in the curative intent management of locally advanced cervical cancer. The introduction of the magnetic resonance (MR) as a preferred image modality and the development of new type of applicators with interstitial components have further improved its benefits. The aim of this work is to review the current status of one important aspect in the cervix cancer brachytherapy procedure, namely catheter reconstruction. MR compatible intracavitary and interstitial applicators are described. Considerations about the use of MR imaging (MRI) regarding appropriate strategies for applicator reconstruction, technical requirements, MR sequences, patient preparation and applicator commissioning are included. It is recommendable to perform the reconstruction process in the same image study employed by the physician for contouring, that is, T2 weighted (T2W) sequences. Nevertheless, a clear identification of the source path inside the catheters and the applicators is a challenge when using exclusively T2W sequences. For the intracavitary component of the implant, sometimes the catheters may be filled with some substance that produces a high intensity signal on MRI. However, this strategy is not feasible for plastic tubes or titanium needles, which, moreover, induce magnetic susceptibility artifacts. In these situations, the use of applicator libraries available in the treatment planning system (TPS) is useful, since they not only include accurate geometrical models of the intracavitary applicators, but also recent developments have made possible the implementation of the interstitial component. Another strategy to improve the reconstruction process is based on the incorporation of MR markers, such as small pellets, to be used as anchor points. Many institutions employ computed tomography (CT) as a supporting image modality. The registration of CT and MR image sets should be carefully performed, and its uncertainty previously assessed. Besides, an important research work is being carried out regarding the use of ultrasound and electromagnetic tracking technologies.

Contrast-enhanced ultrasonography vs MRI for evaluation of local invasion by cervical cancer

OBJECTIVE:

The purpose of this study is to compare contrast-enhanced ultrasound (CEUS) to MRI for evaluating local invasion of cervical cancer.

METHODS:

A total of 108 patients with cervical cancer were included in this study. All the enrolled patients were Stage IIA2-IVB according to the International Federation of Obstetrics and Gynecology and treated with volumetric modulated arc therapy. Tumour size in different dimensions was compared between MRI and CEUS. The correlation coefficients (r) between MRI and CEUS for diagnosing local invasion, parametrial extension, and invasion to vagina, uterine corpus and adjacent organs were assessed.

RESULTS:

Measurements by MRI and CEUS were strongly correlated in the three dimensions: left-right r = 0.84, craniocaudal r = 0.86 and anteroposterior r = 0.88. Vaginal and parametrial invasion were detected by both MRI and CEUS with moderate concordance, and invasion of uterine corpus, bladder and rectum with good concordance.

CONCLUSION:

CEUS is comparable to MRI for measuring tumour size, with good concordance for evaluating invasion of cervical cancer.

ADVANCES IN KNOWLEDGE:

CEUS is a less expensive non-invasive modality for assessment of tumour size and invasion of cervical cancer.

The use of trans-applicator intracavitary ultrasonography in brachytherapy for cervical cancer: phantom study of a novel approach to 3D image-guided brachytherapy

Purpose

To assess the feasibility of applying trans-applicator intracavitary ultrasonography to image-guided brachytherapy for cervical cancer.

Material and methods

For this experiment, a phantom was created and included a polyethylene tube, intended to simulate a tandem applicator, which was inserted into chicken meat and embedded in agar, along with magnetic resonance imaging (MRI)-compatible ovoid applicators. Three-dimensional images of the phantom were obtained using computed tomography (CT), MRI (T2-weighted), and intracavitary ultrasonography sectional images acquired at 1 mm slice intervals. Intracavitary ultrasonography images were acquired from within the simulated tandem applicator using a radial transducer. Magnetic resonance imaging and intracavitary ultrasonography images were manually registered onto CT images. The chicken meat was contoured as the target volume independently on the CT, MRI, and intracavitary ultrasonography images, and the Dice similarity coefficient was used to compare the target volumes. The dose distributions of a sample brachytherapy plan were also evaluated.

Results

Computed tomography, MRI, and intracavitary ultrasonography all visualized the three-dimensional phantom volumes. Intracavitary ultrasonography images depicted the meat with high echoic signals and a border clearly distinguishable from the surrounding agar. The Dice similarity coefficient values for the target volumes on CT vs. MRI, CT vs. intracavitary ultrasonography, and MRI vs. intracavitary ultrasonography were 0.966, 0.965, and 0.971, respectively, indicating similar contouring with the three modalities. Among the modalities, the differences in D₅₀, D₉₀, D₉₈, and D₁₀₀ values were 1.8%, 2.9%, 3.7%, and 2.9%, respectively.

Conclusions

Three-dimensional reconstructed trans-applicator intracavitary ultrasonographic images clearly depicted meat tissue within the phantom, and could thus be used for brachytherapy planning. This study proves the concept of trans-applicator intracavitary ultrasonography for intracavitary brachytherapy. Further research such as development of intracavitary ultrasonography system, 3D reconstruction method, ultrasonography-compatible applicators, and ultrasonography-based target concept is warranted to assess the potential clinical application.

Use of 3D transabdominal ultrasound imaging for treatment planning in cervical cancer brachytherapy: Comparison to magnetic resonance and computed tomography

PURPOSE

To evaluate if the addition of 3D transabdominal ultrasound (3DTAUS) imaging to computed tomography (CT) can improve treatment planning in 3D adaptive brachytherapy when compared with CT-based planning alone, resulting in treatment plans closer to the ones obtained using magnetic resonance imaging (MRI)-based planning.

METHODS AND MATERIALS

Five patients with cervical cancer undergoing brachytherapy underwent three imaging modalities: MRI, CT, and CT-3DTAUS. Volumes were delineated by a radiation oncologist and treatment plans were optimized on each imaging modality. To compare treatment plans, the dwell times optimized on MRI were transferred on CT and CT-3DTAUS images and dose parameters were reported on volumes of the receiving imaging modality. The plans optimized on CT and CT-3DTAUS were also copied and evaluated on MRI images.

RESULTS

Treatment plans optimized and evaluated on the same imaging modalities were clinically acceptable but statistically different (p < 0.05) from one another. MR-based plans had the highest target coverage (98%) and CT-based plans the lowest (93%). For all treatment plans evaluated on MRI, the target coverage was equivalent. However, a decrease in target coverage (V100) was observed when MR-based plans were applied on CT-3DTAUS (6%) and CT (13%) with p < 0.05. An increase in the rectum/sigmoid dose (D2cc) was observed with both CT-3DTAUS-based (0.6 Gy) and CT-based planning (1 Gy) when compared with MR-based plans, whereas bladder dose stayed similar.

CONCLUSIONS

When compared with CT-based planning, the addition of 3DTAUS to CT results in treatment plans closer to MR-based planning. Its use reduces the high-risk clinical target volume overestimation typically observed on CT, improving coverage of the target volume while reducing dose to the organs at risk.

American Brachytherapy Society: Brachytherapy treatment recommendations for locally advanced cervix cancer for low-income and middle-income countries

PURPOSE

Most cervix cancer cases occur in low-income and middle-income countries (LMIC), and outcomes are suboptimal, even for early stage disease. Brachytherapy plays a central role in the treatment paradigm, improving both local control and overall survival. The American Brachytherapy Society (ABS) aims to provide guidelines for brachytherapy delivery in resource-limited settings.

METHODS AND MATERIALS

A panel of clinicians and physicists with expertise in brachytherapy administration in LMIC was convened. A survey was developed to identify practice patterns at the authors' institutions and was also extended to participants of the Cervix Cancer Research Network. The scientific literature was reviewed to identify consensus papers or review articles with a focus on treatment of locally advanced, unresected cervical cancer in LMIC.

RESULTS

Of the 40 participants invited to respond to the survey, 32 responded (response rate 80%). Participants were practicing in 14 different countries including both high-income (China, Singapore, Taiwan, United Kingdom, and United States) and low-income or middle-income countries (Bangladesh, Botswana, Brazil, India, Malaysia, Pakistan, Philippines, Thailand, and Vietnam). Recommendations for modifications to existing ABS guidelines were reviewed by the panel members and are highlighted in this article.

CONCLUSIONS

Recommendations for treatment of locally advanced, unresectable cervical cancer in LMIC are presented. The guidelines comment on staging, external beam radiotherapy, use of concurrent chemotherapy, overall treatment duration, use of anesthesia, applicator choice and placement verification, brachytherapy treatment planning including dose and prescription point, recommended reporting and documentation, physics support, and follow-up.

Improving the efficiency of image guided brachytherapy in cervical cancer

Brachytherapy is an essential component of the treatment of locally advanced cervical cancers. It enables the dose to the tumor to be boosted whilst allowing relative sparing of the normal tissues. Traditionally, cervical brachytherapy was prescribed to point A but since the GEC-ESTRO guidelines were published in 2005, there has been a move towards prescribing the dose to a 3D volume. Image guided brachytherapy has been shown to reduce local recurrence, and improve survival and is optimally predicated on magnetic resonance imaging. Radiological studies, patient workflow, operative parameters, and intensive therapy planning can represent a challenge to clinical resources. This article explores the ways, in which 3D conformal brachytherapy can be implemented and draws findings from recent literature and a well-developed hospital practice in order to suggest ways to improve the efficiency and efficacy of a brachytherapy service. Finally, we discuss relatively underexploited translational research opportunities.

Clinical outcomes from an innovative protocol using serial ultrasound imaging and a single MR image to guide brachytherapy for locally advanced cervix cancer

PURPOSE

The aim of this study was to report clinical outcomes in a series of patients who underwent serial ultrasound and a single MRI to plan and verify intracavitary brachytherapy.

METHODS AND MATERIALS

Data for patients who were referred for curative intent radiotherapy for International Federation of Gynecology and Obstetrics (FIGO) Stage 1-1V cervix cancer between January 2007 and March 2012 were analyzed. All patients received external beam radiotherapy with concurrent chemotherapy and sequential high-dose rate brachytherapy. Brachytherapy was planned and verified using serial ultrasound imaging and a single MRI.

RESULTS

Data from 191 patients were available for analyses. The median (range) followup time was 5.08 (0.25-8.25) years. Five-year local control, failure-free survival, cancer-specific survival, and overall survival were 86%, 57.3%, 70% and 63%, respectively. Mean (standard deviation) combined external beam radiotherapy and brachytherapy target doses, equivalent to doses in 2 Gy fractions were 80.4 Gy10 (3.89), median (range) 80 (49-96) Gy10. Grade 3 or greater gastrointestinal, genitourinary, or vaginal late toxicity occurred in 3%, 1.6%, and 2% of patients, respectively. Survival, patterns of failure, and late complication rates were similar to published series of MRI/CT-based brachytherapy practices.

CONCLUSIONS

This large study demonstrates that favorable treatment outcomes can be obtained using a pragmatic and innovative combination of ultrasound and MR imaging.

Evaluation of uterine ultrasound imaging in cervical radiotherapy; a comparison of autoscan and conventional probe

OBJECTIVE

In cervical radiotherapy, it is essential that the uterine position is correctly determined prior to treatment delivery. The aim of this study was to evaluate an autoscan ultrasound (A-US) probe, a motorized transducer creating three-dimensional (3D) images by sweeping, by comparing it with a conventional ultrasound (C-US) probe, where manual scanning is required to acquire 3D images.

METHODS

Nine healthy volunteers were scanned by seven operators, using the Clarity(®) system (Elekta, Stockholm, Sweden). In total, 72 scans, 36 scans from the C-US and 36 scans from the A-US probes, were acquired. Two observers delineated the uterine structure, using the software-assisted segmentation in the Clarity workstation. The data of uterine volume, uterine centre of mass (COM) and maximum uterine lengths, in three orthogonal directions, were analyzed.

RESULTS

In 53% of the C-US scans, the whole uterus was captured, compared with 89% using the A-US. F-test on 36 scans demonstrated statistically significant differences in interobserver COM standard deviation (SD) when comparing the C-US with the A-US probe for the inferior-superior (p < 0.006), left-right (p < 0.012) and anteroposterior directions (p < 0.001). The median of the interobserver COM distance (Euclidean distance for 36 scans) was reduced from 8.5 (C-US) to 6.0 mm (A-US). An F-test on the 36 scans showed strong significant differences (p < 0.001) in the SD of the Euclidean interobserver distance when comparing the C-US with the A-US scans. The average Dice coefficient when comparing the two observers was 0.67 (C-US) and 0.75 (A-US). The predictive interval demonstrated better interobserver delineation concordance using the A-US probe.

CONCLUSION

The A-US probe imaging might be a better choice of image-guided radiotherapy system for correcting for daily uterine positional changes in cervical radiotherapy.

ADVANCES IN KNOWLEDGE

Using a novel A-US probe might reduce the uncertainty in interoperator variability during ultrasound scanning.

Potential role of TRAns Cervical Endosonography (TRACE) in brachytherapy of cervical cancer: proof of concept

PURPOSE

Magnetic resonance imaging (MRI) is the gold standard for image guided adaptive brachytherapy (BT) of cervical cancer. Ultrasound is an attractive alternative with reasonable costs and high soft tissue depiction quality. This technical note aims to demonstrate the proof of principle for use of TRAns Cervical Endosonography with rotating transducer in the context of brachytherapy (TRACE BT).

MATERIAL AND METHODS

TRACE BT presentation is based on a single stage IIB cervical cancer patient. Prior to second BT implant, rotating US transducer (6.9 mm diameter) was inserted in cervical canal and axial images obtained at 10 MHz, focal range of 30 mm, and axial resolution of 0.4 mm. Size and topography of hypo-echoic areas were assessed and optimal positions of interstitial needles were determined. Finally, intracavitary applicator was placed and needles inserted through vaginal ring-template according to TRACE pre-plan. MRI-based high risk clinical target volume (CTVHR) dimensions were compared with hypoechoic areas on TRACE. Topography of parametrial needles on post-insertion MRI was compared with TRACE pre-plan.

RESULTS

Insertion of rotating mechanism into cervico-uterine cavity was safe, feasible and fast. The 360° imaging in axial plane enabled real-time assessment of cervix, uterus, and adjacent parametria. Qualitative comparison of TRACE with post-insertion MRI revealed favorable agreement of findings. In-plane size of CTVHR on MRI was comparable to hypoechoic areas on TRACE. Needle positions on post-insertion MRI corresponded to TRACE-based pre-plan. Main limitation of TRACE was gradual deterioration of image quality due to coupling gel removal.

CONCLUSIONS

Present proof of concept demonstrates potential role of TRACE-BT for cervical cancer as an attractive high-tech approach with reasonable costs. Prior to investigation of its clinical role, further development of TRACE methodology is needed. This includes reliable transducer-tissue coupling, applicator reconstruction, imaging range, limitations in extensive tumors, US-based contouring concepts, registration with other imaging methods, organ dose-assessment, real-time dosimetry, etc.

Moving from standardized to personalized boxes and pears in radiation planning for cervical cancer

PURPOSE OF REVIEW

We reviewed the most recent literature on advancements in external beam radiation therapy, brachytherapy, and stereotactic body radiation therapy (SBRT) in the treatment of cervical cancer.

RECENT FINDINGS

There is a growing transition from three-dimensional-conformal radiation therapy to intensity modulated radiation therapy, and from point A-based two-dimensional prescriptions to three-dimensional volume-based prescriptions in image-guided brachytherapy (IGBT). These advances allow dose-escalation to at-risk regions while sparing normal tissues. Implementation of these techniques is resulting in improved local control and decreased toxicity in patients. With increased local control, the predominant pattern of recurrence is now distant failure, opening the door for SBRT as an emerging treatment option for select patients with limited numbers of metastases (oligometastatic state).

SUMMARY

The integration of IGBT, as well as dose sculpting with intensity modulated radiation therapy, is improving outcomes in women with locally advanced cervical cancer. The clinical evidence strongly supports moving away from point A-based prescriptions and adopting IGBT techniques. The existing data supporting SBRT for gynecologic oligometastases are more limited and require further research before widespread adoption; however, evidence from other disease sites is promising.

Image Guided Cervical Brachytherapy: 2014 Survey of the American Brachytherapy Society

PURPOSE

To provide an update of the 2007 American brachytherapy survey on image-based brachytherapy, which showed that in the setting of treatment planning for gynecologic brachytherapy, although computed tomography (CT) was often used for treatment planning, most brachytherapists used point A for dose specification.

METHODS AND MATERIALS

A 45-question electronic survey on cervical cancer brachytherapy practice patterns was sent to all American Brachytherapy Society members and additional radiation oncologists and physicists based in the United States between January and September 2014. Responses from the 2007 survey and the present survey were compared using the χ(2) test.

RESULTS

There were 370 respondents. Of those, only respondents, not in training, who treat more than 1 cervical cancer patient per year and practice in the United States, were included in the analysis (219). For dose specification to the target (cervix and tumor), 95% always use CT, and 34% always use MRI. However, 46% use point A only for dose specification to the target. There was a lot of variation in parameters used for dose evaluation of target volume and normal tissues. Compared with the 2007 survey, use of MRI has increased from 2% to 34% (P<.0001) for dose specification to the target. Use of volume-based dose delineation to the target has increased from 14% to 52% (P<.0001).

CONCLUSION

Although use of image-based brachytherapy has increased in the United States since the 2007 survey, there is room for further growth, particularly with the use of MRI. This increase may be in part due to educational initiatives. However, there is still significant heterogeneity in brachytherapy practice in the United States, and future efforts should be geared toward standardizing treatment.

Reproducibility and interoperator reliability of obtaining images and measurements of the cervix and uterus with brachytherapy treatment applicators in situ using transabdominal ultrasound

PURPOSE

To validate interoperator reliability of brachytherapy radiation therapists (RTs) in obtaining an ultrasound image and measuring the cervix and uterine dimensions using transabdominal ultrasound.

METHODS AND MATERIALS

Patients who underwent MRI with applicators in situ after the first insertion were included in the study. Imaging was performed by three RTs (RT1, RT2, and RT3) with varying degrees of ultrasound experience. All RTs were required to obtain a longitudinal planning image depicting the applicator in the uterine canal and measure the cervix and uterus. The MRI scan, taken 1 hour after the ultrasound, was used as the reference standard against which all measurements were compared. Measurements were analyzed with intraclass correlation coefficient and Bland-Altman plots.

RESULTS

All RTs were able to obtain a suitable longitudinal image for each patient in the study. Mean differences (SD) between MRI and ultrasound measurements obtained by RTs ranged from 3.5 (3.6) to 4.4 (4.23) mm and 0 (3.0) to 0.9 (2.5) mm on the anterior and posterior surface of the cervix, respectively. Intraclass correlation coefficient for absolute agreement between MRI and RTs was >0.9 for all posterior measurement points in the cervix and ranged from 0.41 to 0.92 on the anterior surface. Measurements were not statistically different between RTs at any measurement point.

CONCLUSIONS

RTs with variable training attained high levels of interoperator reliability when using transabdominal ultrasound to obtain images and measurements of the uterus and cervix with brachytherapy applicators in situ. Access to training and use of a well-defined protocol assist in achieving these high levels of reliability.

Brachytherapy in cancer cervix: Time to move ahead from point A?

Brachytherapy forms an integral part of the radiation therapy in cancer cervix. The dose prescription for intracavitary brachytherapy (ICBT) in cancer cervix is based on Tod and Meredith's point A and has been in practice since 1938. This was proposed at a time when accessibility to imaging technology and dose computation facilities was limited. The concept has been in practice worldwide for more than half a century and has been the fulcrum of all ICBT treatments, strategies and outcome measures. The method is simple and can be adapted by all centres practicing ICBT in cancer cervix. However, with the widespread availability of imaging techniques, clinical use of different dose-rates, availability of a host of applicators fabricated with image compatible materials, radiobiological implications of dose equivalence and its impact on tumour and organs at risk; more and more weight is being laid down on individualised image based brachytherapy. Thus, computed tomography, magnetic-resonance imaging and even positron emission computerized tomography along with brachytherapy treatment planning system are being increasingly adopted with promising outcomes. The present article reviews the evolution of dose prescription concepts in ICBT in cancer cervix and brings forward the need for image based brachytherapy to evaluate clinical outcomes. As is evident, a gradual transition from "point" based brachytherapy to "profile" based image guided brachytherapy is gaining widespread acceptance for dose prescription, reporting and outcome evaluation in the clinical practice of ICBT in cancer cervix.

Ultrasound guided conformal brachytherapy of cervix cancer: survival, patterns of failure, and late complications

Objective

The aim of this study was to report on the long-term results of transabdominal ultrasound guided conformal brachytherapy in patients with cervical cancer with respect to patterns of failures, treatment related toxicities and survival.

Methods

Three hundred and nine patients with cervical cancer who presented to Institute between January 1999 and December 2008 were staged with magnetic resonance imaging and positron emission tomography and treated with external beam radiotherapy and high dose rate conformal image guided brachytherapy with curative intent. Follow-up data relating to sites of failure and toxicity was recorded prospectively.

Results

Two hundred and ninety-two patients were available for analyses. The median (interquantile range) follow-up time was 4.1 years (range, 2.4 to 6.1 years). Five-year failure free survival and overall survival (OS) were 66% and 65%, respectively. Primary, pelvic, para-aortic, and distant failure were observed in 12.5%, 16.4%, 22%, and 23% of patients, respectively. In multivariate analysis, tumor volume and nodal disease related to survival, whereas local disease control and point A dose did not.

Conclusion

Ultrasound guided conformal brachytherapy of cervix cancer has led to optimal local control and OS. The Melbourne protocol compares favorably to the more technically elaborate and expensive GEC-ESTRO recommendations. The Melbourne protocol's technical simplicity with real-time imaging and treatment planning makes this a method of choice for treating patients with cervical cancer.