Image-Guided Gynecologic Brachytherapy for Cervical Cancer

First implementation of an innovative infra-red camera system integrated into a mobile CBCT scanner for applicator tracking in brachytherapy-Initial performance characterization

PURPOSE

To enable a real-time applicator guidance for brachytherapy, we used for the first time infra-red tracking cameras (OptiTrack, USA) integrated into a mobile cone-beam computed tomography (CBCT) scanner (medPhoton, Austria). We provide the first description of this prototype and its performance evaluation.

METHODS

We performed assessments of camera calibration and camera-CBCT registration using a geometric calibration phantom. For this purpose, we first evaluated the effects of intrinsic parameters such as camera temperature or gantry rotations on the tracked marker positions. Afterward, calibrations with various settings (sample number, field of view coverage, calibration directions, calibration distances, and lighting conditions) were performed to identify the requirements for achieving maximum tracking accuracy based on an in-house phantom. The corresponding effects on camera-CBCT registration were determined as well by comparing tracked marker positions to the positions determined via CBCT. Long-term stability was assessed by comparing tracking and a ground-truth on a weekly basis for 6 weeks.

RESULTS

Robust tracking with positional drifts of 0.02 ± 0.01 mm was feasible using the system after a warm-up period of 90 min. However, gantry rotations affected the tracking and led to inaccuracies of up to 0.70 mm. We identified that 4000 samples and full coverage were required to ensure a robust determination of marker positions and camera-CBCT registration with geometric deviations of 0.18 ± 0.03 mm and 0.42 ± 0.07 mm, respectively. Long-term stability showed deviations of more than two standard deviations from the initial calibration after 3 weeks.

CONCLUSION

We implemented for the first time a standalone combined camera-CBCT system for tracking in brachytherapy. The system showed high potential for establishing corresponding workflows.

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.

Feasibility of quantitative diffusion-weighted imaging during intra-procedural MRI-guided brachytherapy of locally advanced cervical and vaginal cancers

PURPOSE

To determine the feasibility of quantitative apparent diffusion coefficient (ADC) acquisition during magnetic resonance imaging-guided brachytherapy (MRgBT) using reduced field-of-view (rFOV) diffusion-weighted imaging (DWI).

METHODS AND MATERIALS

T2-weighted (T2w) MR and full-FOV single-shot echo planar (ssEPI) DWI were acquired in 7 patients with cervical or vaginal malignancy at baseline and prior to brachytherapy, while rFOV-DWI was acquired during MRgBT following brachytherapy applicator placement. The gross target volume (GTV) was contoured on the T2w images and registered to the ADC map. Voxels at the GTV's maximum Maurer distance comprised a central sub-volume (GTVcenter). Contour ADC mean and standard deviation were compared between timepoints using repeated measures ANOVA.

RESULTS

ssEPI-DWI mean ADC increased between baseline and prebrachytherapy from 1.03 ± 0.18 10-3 mm2/s to 1.34 ± 0.28 10-3 mm2/s for the GTV (p = 0.06) and from 0.84 ± 0.13 10-3 mm2/s to 1.26 ± 0.25 10-3 mm2/s at the level of the GTVcenter (p = 0.03), consistent with early treatment response. rFOV-DWI during MRgBT demonstrated mean ADC values of 1.28 ± 0.14 10-3 mm2/s and 1.28 ± 0.19 10-3 mm2/s for the GTV and GTVcenter, respectively (p = 0.02 and p = 0.03 relative to baseline). No significant differences were observed between ssEPI-DWI and rFOV-DWI ADC measurements.

CONCLUSIONS

Quantitative ADC measurement in the setting of MRI guided brachytherapy implant placement for cervical and vaginal cancers is feasible using rFOV-DWI, with comparable mean ADC comparable to prebrachytherapy ssEPI-DWI, and may enable MRI-guided radiotherapy targeting of low ADC, radiation resistant sub-volumes of tumor.

Dosimetric parameters and safety analysis of 3D-printing non-coplanar template-assisted interstitial brachytherapy for non-centrally recurrent cervical cancer

Introduction

The prognosis of patients with non-central recurrent cervical cancer (NRCC) remains poor, and treatment options are limited. We aimed to explore the accuracy and safety of the 3D-printed non-coplanar template (3D-PNCT)-assisted 192Ir interstitial brachytherapy (ISBT) in the treatment of NRCC.

Material and methods

A total of 36 patients with NRCC who received 3D-PNCT-guided 192Ir ISBT in the First Affiliated Hospital of Zhengzhou University from January 2021 to July 2022 were included in this study. There were 36 3D-PNCTs that were designed and printed. The prescribed dose was 30-36 Gy, divided into five to six times, once a week. To evaluate whether the actual parameters were consistent with the preoperative design, the dosimetric parameters of pre- and postoperative treatment plans were compared, including dose of 90% high-risk clinical target volume (HR-CTV D90), volume percentage of 100% and 150% prescribed dose V100% and V150%, homogeneity index (HI), conformal index (CI), external index (EI), and dose received by 2 cm3 (D2cm3) of the rectum, colon, bladder, and ileum. The safety parameters including occurrence of bleeding, infection, pain, radiation enteritis, and radiation cystitis within 3 months after operation were recorded.

Results

All patients successfully completed the treatment and achieved the goals of the preoperative plan. There was no significant difference in the accuracy (HRCTVD90, V100%, EI, CI, and HI) and safety (D2cm3 of rectum, colon, bladder, and ileum) parameters of the postoperative plan compared with the preoperative plan (all p>0.05). Major side effects included bleeding at the puncture site (13.9%), postoperative pain (8.3%), acute radiation cystitis (13.9%), and radiation enteritis (19.4%). There were no serious perioperative complications and no grade 3-4 acute radiotherapy side effects.

Conclusion

3D-PNCT-assisted 192Ir ISBT can be accurately and safely applied in the treatment of patients with NRCC.

Image-guided adaptive brachytherapy for advanced cervical cancer spreading to the bladder and/or rectum: Clinical outcome and prognostic factors

INTRODUCTION

Refinements of brachytherapy techniques have led to better local control of locally advanced cervical cancer (LACC), especially with the development of image-guided adaptive brachytherapy (IGABT). Data on the efficacy of brachytherapy in cervical cancer spreading to adjacent organs are scarce. We report the experience of our institution in the treatment of these advanced tumors with IGABT.

MATERIALS AND METHODS

Medical records of patients treated for a LACC spreading to the bladder and/or rectum between 2006 and 2020 at Gustave Roussy Institute were analyzed. Dosimetric parameters were collected and converted into 2 Gy per fraction equivalent doses, including the minimal dose received by 90% of the high-risk target volume (D₉₀ CTV_HR) and intermediate-risk target volume (D₉₀ CTV_IR), as well as the dose received by the most exposed 2 cm³ of the organs at risk. A Cox regression model was used to study the potential associations between clinical and dosimetric factors with survival endpoints and fistula formation.

RESULTS AND STATISTICAL ANALYSIS

A total of 81 patients were identified. All patients received pelvic+/- para-aortic radiotherapy, 45 Gy in 25 fractions +/- boost to gross lymph nodes. Concomitant platinum-based chemotherapy was administered in 93.8% of cases. The median D₉₀ CTV_HR dose was 75.5 Gy_EQD2 (SD: 10.39 Gy_EQD2) and median CTV_HR volume was 47.6 cm³ (SD: 27.9 cm³). Median bladder and rectal D2_cm3 dose were 75.04 Gy_EQD2 (SD: 8.72 Gy_EQD2) and 64.07 Gy_EQD2 (SD: 6.68 Gy_EQD2). After a median follow-up of 27.62 ± 25.10 months, recurrence was found in 34/81 patients (42%). Metastatic failure was the most common pattern of relapse (n = 25). Use of a combined interstitial/intracavitary technique and D₉₀ CTV_HR ≥ 75.1 Gy_EQD2 were prognostic factors for OS in univariate analysis (HR = 0.24, 95%IC: 0.057-1, p = 0.023; HR = 0.2, 95%IC: 0.059-0.68, p = 0.0025, respectively). In multivariate analysis, a D₉₀ CTV_HR ≥ 75.1 Gy_EQD2 was significant for OS (HR = 0.23; 95%IC: 0.07, 0.78, p = 0.018). The occurrence of vesicovaginal fistula (VVF) was the most frequent pattern of local recurrence (HR = 4.6, 95%CI: 1.5-14, p = 0.01).

CONCLUSION

Advances in brachytherapy modalities improved local control and survival while reducing toxicities. Enhancing local control through dose escalation and combined intracavitary/interstitial brachytherapy techniques is a major factor in patients cure probability, together with systemic intensification to better control distant events.

Research on Improving Radiotherapy Accuracy Based on Image-Guided Radiotherapy

With the changes of people's diet and lifestyle, the number of patients with abdominal malignant tumors is increasing year by year. In order to analyze the effectiveness of cone-beam CT (CBCT) enhancement technology in improving the accuracy of radiotherapy for clinical malignant tumors, 92 patients with abdominal malignant tumor are divided into the control group and the CBCT radiotherapy group. The experimental results show that precise radiotherapy technology can promote the recovery of the immune function of patients with abdominal malignant tumors, improve the effect of treatment, and decrease the incidence of complications.

The Fusion of MRI and CT in the Planning of Brachytherapy for Cancer of the Uterine Cervix

Introduction: tumors of the uterine cervix are among the most common carcinomas in women. Intracervical brachytherapy is an indispensable part of curative treatment. Although the tumor is significantly more recognizable in MRI than in CT, the practical application of MRI in brachytherapy planning is still difficult. The present study examines the technical possibilities of merging CT and MRI. Materials and Methods: the treatment files and imaging of all 53 patients who had been irradiated by image-guided adaptive brachytherapy (IGABT) between January 2019 and August 2021 at the Department of Radiotherapy of the Hannover Medical School were evaluated, retrospectively. Patients were treated first with an external beam radiotherapy (EBRT) combined with simultaneous chemotherapy. After an average of 4.2 weeks, the preparation for IGABT began. The clinical target volume (CTV) for brachytherapy was contoured first in an MRI acquired before starting EBRT (MRI 1) and once more in a second MRI just before starting IGABT (MRI 2). Then, after inserting the intravaginal applicator, a CT-scan was acquired, and the CTV was contoured in the CT. Finally, the recordings of MRI 1, MRI 2, and the CT were merged, and the congruence of CTVs was quantitatively evaluated. Results: the CTV delineated in MRI 2 was, on average, 28% smaller than that in MRI 1 after an average applied radiation dose of 42 Gy. The CTV delineated in the CT covered an average of no more than 80.8% of the CTV delineated in MRI 2. The congruence of CTVs was not superior in patients with a smit sleeve in the cervical channel, with a 3D-volumetric MRI or with a contrast-enhanced sequence for MRI. Conclusion: the anatomical shape and position of the uterus is significantly changed by introducing a vaginal applicator. Despite the superior delimitability of the tumor in MRI, brachytherapy cannot be reliably planned by the image fusion of an MRI without a vaginal applicator.

Radiotherapy of cervical cancer

External beam radiotherapy and brachytherapy are major treatments in the management of cervical cancer. For early-stage tumours with local risk factors, brachytherapy is a preoperative option. Postoperative radiotherapy is indicated according to histopathological criteria. For advanced local tumours, chemoradiation is the standard treatment, followed by brachytherapy boost, which is not optional. We present the update of the recommendations of the French Society of Oncological Radiotherapy on the indications and techniques for external beam radiotherapy and brachytherapy for cervical cancer.

Molecular Markers to Predict Prognosis and Treatment Response in Uterine Cervical Cancer

Uterine cervical cancer is one of the leading causes of cancer-related mortality in women worldwide. Each year, over half a million new cases are estimated, resulting in more than 300,000 deaths. While less-invasive, fertility-preserving surgical procedures can be offered to women in early stages, treatment for locally advanced disease may include radical hysterectomy, primary chemoradiotherapy (CRT) or a combination of these modalities. Concurrent platinum-based chemoradiotherapy regimens remain the first-line treatments for locally advanced cervical cancer. Despite achievements such as the introduction of angiogenesis inhibitors, and more recently immunotherapies, the overall survival of women with persistent, recurrent or metastatic disease has not been extended significantly in the last decades. Furthermore, a broad spectrum of molecular markers to predict therapy response and survival and to identify patients with high- and low-risk constellations is missing. Implementation of these markers, however, may help to further improve treatment and to develop new targeted therapies. This review aims to provide comprehensive insights into the complex mechanisms of cervical cancer pathogenesis within the context of molecular markers for predicting treatment response and prognosis.

[Can stereotactic body radiotherapy replace brachytherapy for locally advanced cervical cancer? French society for radiation oncology statement]

Brachytherapy is part of the treatment of locally advanced cervical cancers, accounting for about half of the total delivered dose. The benefit of dose escalation is the most important in advanced cases or if the tumor has responded poorly. The use of interstitial implantations makes it possible to reach doses of the order of 85 to 90Gy (including external beam radiotherapy contribution) in most patients, through image-guided approaches. Brachytherapy delivery is one of the quality criteria for patient care. To date, no data allow us to consider as an alternative the use of external boost through intensity-modulated or stereotactic body radiotherapy. Indeed, the doses delivered to the tumor and the capacity to spare normal tissues remains lower, as compared to what is permitted by brachytherapy. It is therefore appropriate for centers that do not have access to the technique to establish networks with centers where brachytherapy is performed, to allow each patient to have access to the technique. It is also necessary to promote brachytherapy teaching. The issue of reimbursement will be crucial in the coming years to maintain expertise that is today insufficiently valued in its financial aspects, but has a very high added value for patients.