Dosimetric feasibility of computed tomography-based image-guided brachytherapy in locally advanced cervical cancer: a Japanese prospective multi-institutional study

Evaluation of plan quality, safety, and toxicity of brachytherapy for locally advanced cervical cancer in an Australian setting following changes in prescription and applicator design

INTRODUCTION

Chemoradiotherapy with MRI-guided brachytherapy boosts is the standard of care for locally advanced cervical cancer. Data from the RetroEMBRACE and EMBRACE I trials provide dose-response curves for target volumes and OAR. This study evaluated plan quality, safety and toxicity following escalation of the CTV_HR D90 prescription from 80-90 Gy to 85-95 Gy for two different applicator designs.

METHODS

A retrospective dosimetric plan quality review was undertaken for consecutively treated locally advanced cervical cancer brachytherapy boosts between 2017 and 2022, and the relationships between implant total reference air kerma (TRAK), CTV_HR volume and vaginal dose were investigated. Safety and ≤grade 3 toxicity results were evaluated.

RESULTS

Seventy patients were identified. All patients received a CTV_HR D90 dose >85 Gy and rectum D2cm3 of <75 Gy, while 88.6% of patients received a bladder D2cm3 <90 Gy. Needles were used in 48.6% of patients, and the mean percentage needle TRAK was 38.2%. Increasing the percentage of needle TRAK decreased vaginal TRAK. Sixty-three patients had more than 12 months of follow-up (median 27 months). From this cohort, grade 3 or higher toxicity for vaginal, genitourinary, gastrointestinal and fistula events were seen in 3.2%, 1.6%, 0% and 3.2% of patients, respectively.

CONCLUSION

Increased dose prescriptions and a change of applicator design were successfully adopted into an Australian practice. Applicator design and interstitial needle use affect the plan quality and ability to meet OAR dose constraints following target dose escalation. No safety concerns with needle use or dose escalation were identified.

High-dose-rate brachytherapy in uterine cervix carcinoma: a comparison of dosimetry and clinical outcomes among three fractionation schedules

Background

To assess the differences among three dose-fractionation schedules of image-guided adaptive brachytherapy (IGABT) in cervical squamous cell carcinoma (CSCC) by comparing the dosimetry and clinical outcomes.

Methods

Forty-five patients with CSCC who underwent chemoradiotherapy and IGABT were retrospectively enrolled and divided into three groups based on their dose-fractionation schedules of brachytherapy as: Group-5.5 (5.5 Gy × 6 fractions), Group-6.0 (6.0 Gy × 5 fractions), and Group-7.0 (7.0 Gy × 4 fractions). The analyzed dose-volume histogram parameters included D90% and D98% of the high-risk clinical target volume (HR-CTV), D90% and D98% of intermediate-risk clinical target volume (IR-CTV), and D0.1cc and D2cc of the organs-at-risk (OARs, namely the bladder, rectum, sigmoid and small intestine). Furthermore, the therapeutic efficacy and late toxicities were also compared among the three groups.

Results

The doses of HR-CTV and IR-CTV in Group-5.5 were found to be the highest among the three groups, followed by those in Group-6.0. Significant differences were found for the doses of HR-CTV between Group-5.5 and the other groups. There were no significant differences in the bladder, sigmoid and small intestine dose among the three groups. However, Group-6.0 yielded the lowest rectum received doses, with a significant difference in D0.1cc being detected between Group-6.0 and Group-5.5. The median follow-up time was 30.08 months [range, 6.57-46.3]. The numbers of patients with complete response in Group-5.5, Group-6.0 and Group-7.0 were 13, 14 and 14, respectively (P > 0.05). In regard to the toxicitiy, the incidence of radiation cystitis and proctitis in Group-6.0 was lower than that in Group-5.5 and Group-7.0 (P > 0.05).

Conclusions

The dose-fractionation schedule of 6.0 Gy × 5 fractions provided the most beneficial effects with relatively low OARs doses, suggesting that this dose-fractionation schedule should be prioritized in the clinical application of brachytherapy in cervical cancer.

Effective timing of hyaluronate gel injection in image-guided adaptive brachytherapy for uterine cervical cancer: a proposal of the 'adjusted dose score'

Hyaluronate gel injection (HGI) in the rectovaginal septum and vesicovaginal septum is effective in the setting of high-dose-rate image-guided adaptive brachytherapy (IGABT) for cervical cancer. We aimed to retrospectively investigate optimal conditions for HGI to achieve optimal dose distribution with a minimum number of HGI. We classified 50 IGABT plans of 13 patients with cervical cancer who received IGABT both with and without HGI in the rectovaginal septum and vesicovaginal septum into the following two groups: plan with (number of plans = 32) and plan without (number of plans = 18) HGI. The irradiation dose parameters of high-risk clinical target volume (CTVHR) and organs at risk per fraction were compared between these groups. We also developed the adjusted dose score (ADS), reflecting the overall irradiation dose status for four organs at risk and CTVHR in one IGABT plan and investigated its utility in determining the application of HGI. HGI reduced the maximum dose to the most exposed 2.0 cm3 (D2.0 cm3) of the bladder while increasing the minimum dose covering 90% of CTVHR and the percentage of CTVHR receiving 100% of the prescription dose in one IGABT plan without causing any associated complications. An ADS of ≥2.60 was the optimum cut-off value to decide whether to perform HGI. In conclusion, HGI is a useful procedure for improving target dose distribution while reducing D2.0 cm3 in the bladder in a single IGABT plan. The ADS can serve as a useful indicator for the implementation of HGI.

Transvaginal approach combined intracavitary and interstitial brachytherapy assisted by transrectal ultrasound: results from 30 patients with locally advanced cervical cancer

PURPOSE

This study evaluated the efficacy and safety of transvaginal approach combined intracavitary and interstitial brachytherapy (IC/IS BT) assisted by transrectal ultrasound (TRUS) for treatment of locally advanced cervical cancer (LACC).

MATERIALS AND METHODS

A total of 30 patients of LACC treated with external beam radiotherapy and IC/IS BT via transvaginal approach assisted by transrectal ultrasound were observed retrospectively. The 2-year local control (LC), progression-free survival (PFS), and overall survival (OS) were analyzed using the Kaplan-Meier method. Late adverse events were also evaluated to assess the safety of IC/IS BT.

RESULTS

The median follow-up period was 22 months. The 2-year LC, PFS, and OS were 90%, 61%, and 82%, respectively. We observed no critical complications related to the IC/IS BT technique. Late adverse events of grade 3 or more included one case of grade 4 colon perforation.

CONCLUSION

Our patient series demonstrated that radiotherapy combined with transvaginal approach, TRUS-assisted IC/IS BT achieves favorable local control and safety for LACC.

Improvement in radiation techniques for locally advanced cervical cancer during the last two decades

Since the National Cancer Institute (NCI) alert of concurrent chemoradiotherapy, radiotherapy has been changed from external beam radiotherapy plus brachytherapy to platinum-based concurrent chemoradiotherapy. Therefore, concurrent chemoradiotherapy plus brachytherapy has become a standard treatment for locally advanced cervical cancer. Simultaneously, definitive radiotherapy has been changed gradually from external beam radiotherapy plus low-dose-rate intracavitary brachytherapy to external beam radiotherapy plus high-dose-rate intracavitary brachytherapy. Cervix cancer is uncommon in developed countries; hence, international collaborations have been critical in large-scale clinical trials. The Cervical Cancer Research Network (CCRN), created from the Gynecologic Cancer InterGroup (GCIG), has investigated various concurrent chemotherapy regimens and sequential methods of radiation and chemotherapy. Most recently, many clinical trials of combining immune checkpoint inhibitors with radiotherapy have been ongoing for sequential or concurrent settings. During the last decade, the method of standard radiation therapy has changed from three-dimensional conformal radiation therapy to intensity-modulated radiation therapy for external beam radiotherapy and from two-dimensional to three-dimensional image-guided approaches for brachytherapy. Recent improvements include stereotactic ablative body radiotherapy and MRI-guided linear accelerator (MRI-LINAC) using adaptive radiotherapy. Here we review the current progress of radiation therapy during the last two decades.

Dosimetric comparison of rectal dose-reductive techniques in intra-cavitary brachytherapy for cervical cancer: A retrospective analysis

Purpose

Rectal complications in radiotherapy for cervical cancer can highly affect quality of life and correlate with rectal dose. Vaginal gauze packing (VP) and rectal retraction (RR) are widely used for rectal dose reduction in high-dose-rate brachytherapy. We aimed to perform a dosimetric comparison of these two methods for three-dimensional image-guided adaptive brachytherapy.

Material and methods

We retrospectively examined 50 patients with cervical cancer treated with definitive radiotherapy, including intra-cavitary brachytherapy, performed with VP and RR. We extracted two fractions for each patient: one fraction with VP and the next fraction with RR, and then compared dose-volume parameters. In total, 50 fractions each were analyzed in VP and RR groups. Dose to 90% (D90) of high-risk clinical target volume (HR-CTV), and minimum dose to most exposed 2.0 cm3 of other organs at risk (D2cm3) for the rectum and bladder were determined from planning computed tomography.

Results

There were no significant differences between VP and RR in D90 of HR-CTV (mean: 7.479 Gy and 7.652 Gy, respectively, p = 0.172). The D2cm3 values for the rectum (mean: 4.234 Gy vs. 4.627 Gy, p = 0.008) and bladder (mean: 5.959 Gy vs. 6.690 Gy, p < 0.001) were significantly lower with VP compared with RR.

Conclusions

VP reduced the dose to the rectum and bladder when compared with RR without impairing the dose to CTV.

Patient-Derived Training Simulator for Image-Guided Adaptive Brachytherapy of Locally Advanced Cervical Cancers: Development and Initial Use

Image-guided adaptive brachytherapy (IGABT) using intracavitary and interstitial (IC/IS) techniques plays a pivotal role in definitive radiotherapy for locally advanced cervical cancers. However, the training opportunities for interstitial needle application are limited, preventing this technique from becoming widespread. This study aimed to develop a training simulator for IC/IS brachytherapy. The simulator consists of a soft silicone tumor phantom and acrylic tube mimicking the vagina; it has high visibility because of translucent materials and is compatible with computed tomography (CT) and magnetic resonance imaging (MRI). A patient harboring a typical bulky and irregular-shaped cervical tumor was selected from 495 in-house IGABT-treated candidates, and a tumor phantom (68 × 49 × 45 mm) modeled on this patient was produced from three-dimensional real-scale measurements of the MRI-based high-risk clinical target volume at first brachytherapy. In trial use by two physicians with different levels of IGABT skills, a Fletcher-Suit Asian Pacific applicator, and a Venezia applicator with interstitial needles were nicely applied to the simulator, facilitating successful creation of CT-based treatment plans consistent with clinical practice. Thus, the training simulator can be useful for the training of IC/IS brachytherapy, and warrants further research employing a greater number of phantoms and practitioners to verify its educational value.

Japanese Society for Radiation Oncology Consensus Guidelines of combined intracavitary and interstitial brachytherapy for gynecological cancers

It has been postulated that the combination of intracavitary and interstitial brachytherapy (IC/IS) is effective and safe for large and irregularly shaped uterine cervical cancer patients. However, due to its invasiveness compared to conventional intracavitary brachytherapy (ICBT), it has to be said that the implementation speed of IC/IS is slow. Until now, there have been no guidelines for required equipment, human resources, and procedural guide focusing solely on IC/IS. The purpose of this guideline is to provide radiation oncologists and medical physicists who wish to start IC/IS with practical and comprehensive guidance for a safe IC/IS introduction and to help accelerate the spread of the utilization of IC/IS nationwide. This is the English translation of the Japanese IC/IS Guidelines, and it was created in an effort to share the Japanese approach to the management of locally advanced uterine cervical cancer worldwide.

Clinical advantage and outcomes of computed tomography-based transvaginal hybrid brachytherapy performed only by sedation without general or saddle block anesthesia

BACKGROUND

Three-dimensional image-guided brachytherapy is the standard of care in cervical cancer radiotherapy. In addition, the usefulness of the so-called "hybrid brachytherapy (HBT)" has been reported, which involves the addition of needle applicators to conventional intracavitary brachytherapy for interstitial irradiation.

AIM

To evaluate the clinical outcomes of CT-based HBT consisting of transvaginal insertion of needle applicators (CT-based transvaginal HBT) and only intravenous sedation without general or saddle block anesthesia.

METHODS AND RESULTS

This is a retrospective chart review of patients who received definitive radiotherapy, including CT-based transvaginal HBT, between February 2012 and July 2019. The inclusion criteria were as follows: (i) histologically diagnosed disease, (ii) untreated cervical cancer, (iii) International Federation of Gynecology and Obstetrics (FIGO) stage IB1-IVA disease in the 2008 FIGO staging system, and (iv) patients who underwent CT-based transvaginal HBT at least once in a series of intracavitary brachytherapy. Overall, 54 patients fulfilled the eligibility criteria in the present study. The median follow-up period was 32 (IQR, 19-44) months. No patient complained of symptoms such as persistent bleeding or abdominal pain after the treatment. The 3-year local control (LC), disease-free survival, and overall survival rates for all 54 patients were 86.6%, 60.3%, and 90.7% (95% CI [81.3%-100.0%]), respectively. The 3-year LC rate was 87.7% in patients with FIGO III-IVA and 90.4% in tumor size >6.0 cm. The incidence rate of late adverse events, grade ≥3, in the rectum and bladder was 0% and 1.8%, respectively. In the dose-volume histogram analyses, transvaginal HBT increased the dose of HR-CTV_D90 by ~7.5% without significantly increasing the dose of organs at risk.

CONCLUSION

Considering the favorable clinical outcomes, CT-based transvaginal HBT may be a good option for treating cervical cancer.