Clinical Use of the Utrecht Applicator for Combined Intracavitary/Interstitial Brachytherapy Treatment in Locally Advanced Cervical Cancer

Attention 3D U-NET for dose distribution prediction of high-dose-rate brachytherapy of cervical cancer: Direction modulated brachytherapy tandem applicator

BACKGROUND

Direction Modulated Brachytherapy (DMBT) enables conformal dose distributions. However, clinicians may face challenges in creating viable treatment plans within a fast-paced clinical setting, especially for a novel technology like DMBT, where cumulative clinical experience is limited. Deep learning-based dose prediction methods have emerged as effective tools for enhancing efficiency.

PURPOSE

To develop a voxel-wise dose prediction model using an attention-gating mechanism and a 3D UNET for cervical cancer high-dose-rate (HDR) brachytherapy treatment planning with DMBT six-groove tandems with ovoids or ring applicators.

METHODS

A multi-institutional cohort of 122 retrospective clinical HDR brachytherapy plans treated to a prescription dose in the range of 4.8-7.0 Gy/fraction was used. A DMBT tandem model was constructed and incorporated onto a research version of BrachyVision Treatment Planning System (BV-TPS) as a 3D solid model applicator and retrospectively re-planned all cases by seasoned experts. Those plans were randomly divided into 64:16:20 as training, validating, and testing cohorts, respectively. Data augmentation was applied to the training and validation sets to increase the size by a factor of 4. An attention-gated 3D UNET architecture model was developed to predict full 3D dose distributions based on high-risk clinical target volume (CTVHR) and organs at risk (OARs) contour information. The model was trained using the mean absolute error loss function, Adam optimization algorithm, a learning rate of 0.001, 250 epochs, and a batch size of eight. In addition, a baseline UNET model was trained similarly for comparison. The model performance was evaluated on the testing dataset by analyzing the outcomes in terms of mean dose values and derived dose-volume-histogram indices from 3D dose distributions and comparing the generated dose distributions against the ground-truth dose distributions using dose statistics and clinically meaningful dosimetric indices.

RESULTS

The proposed attention-gated 3D UNET model showed competitive accuracy in predicting 3D dose distributions that closely resemble the ground-truth dose distributions. The average values of the mean absolute errors were 1.82 ± 29.09 Gy (vs. 6.41 ± 20.16 Gy for a baseline UNET) in CTVHR, 0.89 ± 1.25 Gy (vs. 0.94 ± 3.96 Gy for a baseline UNET) in the bladder, 0.33 ± 0.67 Gy (vs. 0.53 ± 1.66 Gy for a baseline UNET) in the rectum, and 0.55 ± 1.57 Gy (vs. 0.76 ± 2.89 Gy for a baseline UNET) in the sigmoid. The results showed that the mean absolute error (MAE) for the bladder, rectum, and sigmoid were 0.22 ± 1.22 Gy (3.62%) (p = 0.015), 0.21 ± 1.06 Gy (2.20%) (p = 0.172), and -0.03 ± 0.54 Gy (1.13%) (p = 0.774), respectively. The MAE for D90, V100%, and V150% of the CTVHR were 0.46 ± 2.44 Gy (8.14%) (p = 0.018), 0.57 ± 11.25% (5.23%) (p = 0.283), and -0.43 ± 19.36% (4.62%) (p = 0.190), respectively. The proposed model needs less than 5 s to predict a full 3D dose distribution of 64 × 64 × 64 voxels for any new patient plan, thus making it sufficient for near real-time applications and aiding with decision-making in the clinic.

CONCLUSIONS

Attention gated 3D-UNET model demonstrated a capability in predicting voxel-wise dose prediction, in comparison to 3D UNET, for DMBT intracavitary brachytherapy planning. The proposed model could be used to obtain dose distributions for near real-time decision-making before DMBT planning and quality assurance. This will guide future automated planning, making the workflow more efficient and clinically viable.

Outcomes and comparison of dosimetric parameters between intracavitary (Fletcher) and combined intracavitary/interstitial (Utrecht) brachytherapy in locally advanced cervical cancer

OBJECTIVE

To report outcomes of combined intracavitary/interstitial (IC/IS) image-guided brachytherapy (IGBT) in locally advanced cervical cancer, and to compare its dosimetric parameters with intracavitary-only (IC) brachytherapy in a first-in-country experience.

METHODS AND MATERIALS

Between January 2021 and September 2022, a total of 160 insertions were done in 40 patients with FIGO IB3-IVA cervical cancer undergoing IGBT using a hybrid (Utrecht) applicator. Corresponding treatment plans for IC brachytherapy were generated during treatment, and optimized. A preplanned comparison of dosimetric parameters, defined in GEC-ESTRO was conducted.

RESULTS

The clinical use of a hybrid IC/IS applicator was feasible in all insertions. An average of 14 needles were inserted in each patient over four fractions. Mean HR-CTV D90 and D98 was 86 (SD 1.9) Gy and 75.7 (SD 2.3) Gy using hybrid applicator, and 80 (SD 5.4) Gy and 69.8 (SD 5.2) Gy using IC applicator, with a mean dose gain of 6.0 (SD 5.0) Gy and 5.9 (SD 4.7) Gy (p <0.001), respectively. Likewise, mean D2cc for bladder and sigmoid were significantly lower in the hybrid technique. Mean contribution of brachytherapy to total HR-CTV D90 (in absolute EQD2 Gy) was 41.7 Gy using IC/IS applicator while 35.7 Gy for IC-only applicator (p = 0.027). Clinical response at 12 weeks showed an overall response rate (ORR) and complete response (CR) rates of 92.5% and 77.5%, respectively.

CONCLUSIONS

IGBT using a hybrid IC/IS applicator showed excellent tolerability and yielded favorable results, resulting in significant dosimetric improvement in terms of primary target dose, and sparing OARs.

Utilizing a novel hybrid brachytherapy technique FINITO (Freehand Interstitial Needles in addition to Tandem and Ovoid) for locally advanced cervical cancer

PURPOSE

We aimed to assess the clinical feasibility and advantages of using a novel hybrid brachytherapy technique by placing Freehand Interstitial Needles in addition to the Tandem and Ovoid applicator (FINITO) for the treatment of locally advanced cervical cancer (LAC).

METHODS AND MATERIALS

A retrospective analysis was performed on two cohorts of patients with LACC treated at our institution: 29 patients in the FINITO group and 17 patients in the control group using T&O only approach. Clinical outcomes of interest included local control (LC), progression-free survival (PFS), overall survival (OS), and rates of acute and late toxicities. Kaplan-Meier methodology was used to estimate OS, PFS, and LC. Wilcoxon signed-rank test was used to compare the median values for dosimetry parameters. A p-value of ≤ 0.05 was considered statistically significant. All statistical analyses were performed using RStudio.

RESULTS

At a median of 2 years there was no difference in rates of OS, PFS or LC between the FINITO and the control group of patients. The 2-year OS, PFS, and LC for the FINITO group were 59% (95% CI 34%-100%), 58% (95% CI 38%-89%), and 84% (95% CI 69%-100%), respectively. Late toxicities were significantly lower in the FINITO group for both gastrointestinal and genitourinary symptoms (p = 0.001 and 0.01, respectively) as compared to the T&O group.

CONCLUSION

Based on the equivalent LC rate and lower toxicity profile, our FINITO technique appears to be an excellent alternative to the standard intracavitary brachytherapy in patients with advanced disease, especially in resource-limited settings.

The Effect of Contemporary Brachytherapy Practices on Prognosis in Women with Locally Advanced Cervical Cancer

(1) Background: Over the past two decades use of new imaging modalities and the adaptation of applicators have allowed for advances in volumetric (3D) imaging-based brachytherapy practices for patients with locally advanced cervical cancer. The aim of this study was to compare the oncological outcome and toxicity for three consecutively introduced brachytherapy practices in a large single-center cohort; (2) Methods: Patients treated for cervical cancer with primary radiotherapy and curative intent were consecutively included in this retrospective, single-center cohort study from 2006 to 2019. This cohort was divided into three groups (CT, MRI, and MRI+needles) based on the timing of the introduction of a novel brachytherapy practice; 3D brachytherapy planning using CT- and MRI-guided adaptive brachytherapy and the use of parametrial interstitial needles, respectively. Actuarial estimates were compared between groups. Multivariable Cox regression analyses were performed to correct for other risk factors. Crude rates of severe (≥grade 3) late toxicity were reported; (3) Results: A total of 397 patients were included in this cohort. At a median follow-up of 40 months (interquartile range (IQR) 22-62), actuarial 3-year local control, pelvic control, disease-free survival, and overall survival for the entire cohort were 91% (95% (Confidence Interval (CI)) 88-94), 88% (95% CI 84-91), 69% (95% CI 64-74), and 75% (95% CI 70-79), respectively). Local control, disease-free survival, and overall survival were significantly improved in the MRI+needles group compared to the CT group (p = 0.040, p = 0.004, and p < 0.001, respectively). Independent risk factors for overall survival were treatment in either the CT or MRI group (vs. MRI+needles), older age at diagnosis, adeno (squamous) carcinoma, FIGO stage III/IV, and lymph node metastases. The crude rate of severe late toxicity was 27% in the CT, 26% in the MRI, and 20% in the MRI+needles group; (4) Conclusions: Prognosis in women with locally advanced cervical cancer treated with state-of-the-art MRI-guided adaptive brachytherapy combined with parametrial interstitial needles compares favorably to patients treated with more traditional CT only based brachytherapy.

Characteristics of preplan-based three-dimensional individual template-guided brachytherapy compared to freehand implantation

Image-guided adaptive intracavitary/interstitial brachytherapy (IC/IS IGABT) has exhibited superior dosimetry advantage and local control for locally advanced cervical cancer (LACC). Our group designed a type of cylindrical three-dimensional (3D) printed vaginal template combining an intracavitary applicator with straight and oblique interstitial needles according to the preplan on computed tomography images. This work aimed to research the consistency of the preplan with the treatment plan at every fraction to verify the practical guiding significance of the preplan. We also investigated the difference between 3D-printed template-guided implantation compared with freehand implantation for LACC. Twenty-six patients were treated with 3D-printed individual templates (3D template group), and 20 patients were treated by using freehand insertion (freehand group). Patients in the 3D template group would take a preplan one week before treatment to design and print the individual template, while the freehand group did not. All patients accepted volumetric rotational intensity-modulated radiotherapy at a dose of 49.4 Gy in 26 fractions and subsequent brachytherapy at a dose of 26 Gy in four fractions. All analyses were performed by utilizing SPSS 26. The insertion depth was decreased in fractions 1 and 4 compared with the preplan. None of the dose volume histogram parameters of fractions 1-3, nor the D_2cc of bladder and bowel at fraction 4 were barely changed compared with the preplan. The D₉₀ and D₉₈ of the high-risk clinical target volume in the 3D template group were statistically higher than those in the freehand group (p < 0.01). The D_2cc of the rectum, bladder, bowel, and sigmoid in the 3D template group were all lower than those in the freehand group (p < 0.01). The preplan in this research is consistent with treatment plans, which is important to ensure the feasibility of applying a 3D-printed template in brachytherapy. The 3D-printed individual guidance template was an effective method in brachytherapy for locally advanced cervical cancer.

A novel approach for Venezia ovoid commissioning with a comprehensive analysis of source positions in high-dose-rate brachytherapy

PURPOSE

The lunar design of a Venezia ovoid makes commissioning of the applicator very challenging with traditional autoradiography. In this study, we propose a novel solution to ovoid commissioning and a quality assurance (QA) workflow to effectively assess the entire source path.

METHODS AND MATERIALS

A two-step commissioning process, using electron radiation and radiochromic films, was developed to verify the most distal source position. The ovoid was first attached to a film and was irradiated with a 12 MeV linac beam. This process was repeated on a separate, unexposed film, followed by irradiating it with a HDR source at the most distal position. Two lengths, including the ovoid thickness and the distance between the irradiated spot and the ovoid's outer surface, were obtained from the films' intensity maps. The offset value was calculated from the subtraction of the two measured lengths. Besides acquiring the offset, a source positional simulator (SPS) and a series of planar x-rays from two orthogonal orientations were used to characterize source movement within the ovoid.

RESULTS

Compared to x-ray-based autoradiography, the electron exposure significantly improved the ovoid's visibility on film. Our approach did not use surrogate, which further improved measurement outcomes by decreasing inherent uncertainties. The SPS results suggested the source movement was complex within the cervicovaginal area, but it was predictable with the proposed QA workflow.

CONCLUSION

We introduced a novel, surrogate-free method to commission the Venezia ovoid, which facilitated a manual applicator reconstruction. Additionally, we recommended QA multiple source positions to safely use the ovoid in clinical settings.

Intracavitary brachytherapy with additional Heyman capsules in the treatment of cervical cancer

PURPOSE

Brachytherapy is a mandatory component of primary radiochemotherapy in cervical cancer. The dose can be applied with a traditional intracavitary approach (IC alone) or with multiple catheter brachytherapy to optimize dose distribution in an individual concept. We therefore evaluated whether the utilization of a tandem-ring applicator plus additional intracavitary applicators (add IC) provides an advantage over the traditional IC alone approach, as this method is less time consuming and less invasive compared to a combined intracavitary/interstitial brachytherapy.

METHODS

Twenty three procedures of intracavitary brachytherapy for cervical cancer with additional intracavitary applicators performed in seven patients treated between 2016 and 2018 in our institution were included in this study. Plans were optimized for D90 HR-CTV with and without the utilization of the additional applicators and compared by statistical analysis.

RESULTS

D90 for HR-CTV was 5.71 Gy (±1.17 Gy) for fractions optimized with add IC approach and 5.29 Gy (±1.24 Gy) for fractions without additional applicators (p < 0.01). This translates to a calculated mean EQD2 HR-CTV D90 of 80.72 Gy (±8.34 Gy) compared to 77.84 Gy (±8.49 Gy) after external beam therapy and four fractions of brachytherapy for add IC and IC alone, respectively (p < 0.01). The predictive value of improved coverage of HR-CTV in the first fraction was high.

CONCLUSION

In a subgroup of cases, the addition of intracavitary Heyman capsules can be an alternative to interstitial brachytherapy to improve the plan quality compared to standard IC alone brachytherapy. The benefit from the addition of applicators in the first fraction is predictive for the following fractions.

A Novel Workflow with a Customizable 3D Printed Vaginal Template and a Direction Modulated Brachytherapy (DMBT) Tandem Applicator for Adaptive Interstitial Brachytherapy of the Cervix

A novel clinical workflow utilizing a direction modulated brachytherapy (DMBT) tandem applicator in combination with a patient-specific, 3D printed vaginal needle-track template for an advanced image-guided adaptive interstitial brachytherapy of the cervix. The proposed workflow has three main steps: (1) pre-treatment MRI, (2) an initial optimization of the needle positions based on the DMBT tandem positioning and patient anatomy, and a subsequent inverse optimization using the combined DMBT tandem and needles, and (3) rapid 3D printing. We retrospectively re-planned five patient cases for two scenarios; one plan with the DMBT tandem (T) and ovoids (O) with the original needle (ND) positions (DMBT + O + ND) and another with the DMBT T&O and spatially reoptimized needles (OptN) positions (DMBT + O + OptN). All retrospectively reoptimized plans have been compared to the original plan (OP) as well. The accuracy of 3D printing was verified through the image registration between the planning CT and the CT of the 3D-printed template. The average difference in D_2cc for the bladder, rectum, and sigmoid between the OPs and DMBT + O + OptNs were -8.03 ± 4.04%, -18.67 ± 5.07%, and -26.53 ± 4.85%, respectively. In addition, these average differences between the DMBT + O + ND and DMBT + O + OptNs were -2.55 ± 1.87%, -10.70 ± 3.45%, and -22.03 ± 6.01%, respectively. The benefits could be significant for the patients in terms of target coverage and normal tissue sparing and increase the optimality over free-hand needle positioning.

The Kelowna template for combined intracavitary and interstitial brachytherapy for gynecologic malignancies: Design, application, treatment planning, dosimetric and treatment outcomes

PURPOSE

We report the feasibility, experience, and early outcomes of the combined intracavitary and interstitial dedicated applicator using the Kelowna GYN template (Varian, Palo Alto, CA).

METHODS AND MATERIALS

The Kelowna GYN template is CT compatible and used for the treatment of gynecologic cancers. In cases with patients that have an intact uterus, a modified applicator system using the Kelowna GYN template and a 3D printed adapter piece allows for compatibility with an intrautaerine tandem.

RESULTS

We reviewed the treatment course of 23 patients comprising of 86 fractions of HDR treatment. Median D90 for cervical tumors (n = 7) was 82.4 Gy (range 77.7-92.6); for postoperative cervical tumors (n = 2) was 73.9 Gy (range 72.0-5.8); for vaginal tumors (n = 4) was 85.8 Gy (range 79.8-88.1); for recurrent endometrial (n = 10) was 86.9 Gy (range 74.8-103.2). Median EQD2 D2cc for bladder was 72.4 Gy (range 47.7-99.4), for rectum was 61.2 Gy (range 52.4-80.6), and for sigmoid colon of 50.5 Gy (44.3-66.9). At a median follow-up of 12 months, 2 patients had a local recurrence. Two patients had distant recurrence: one with carcinomatosis at 6 months, and one with pulmonary metastases at 3 months. No patients had late grade three toxicities.

CONCLUSIONS

Our single institutional experience supports the use of the Kelowna template as a robust system as a combined IC-IS applicator resulting in versatile and reproducible implants for a variety of gynecologic malignancies.

Review on Treatment Planning Systems for Cervix Brachytherapy (Interventional Radiotherapy): Some Desirable and Convenient Practical Aspects to Be Implemented from Radiation Oncologist and Medical Physics Perspectives

Intracavitary brachytherapy (BT, Interventional Radiotherapy, IRT), plays an essential role in the curative intent of locally advanced cervical cancer, for which the conventional approach involves external beam radiotherapy with concurrent chemotherapy followed by BT. This work aims to review the different methodologies used by commercially available treatment planning systems (TPSs) in exclusive magnetic resonance imaging-based (MRI) cervix BT with interstitial component treatments. Practical aspects and improvements to be implemented into the TPSs are discussed. This review is based on the clinical expertise of a group of radiation oncologists and medical physicists and on interactive demos provided by the software manufacturers. The TPS versions considered include all the new tools currently in development for future commercial releases. The specialists from the supplier companies were asked to propose solutions to some of the challenges often encountered in a clinical environment through a questionnaire. The results include not only such answers but also comments by the authors that, in their opinion, could help solve the challenges covered in these questions. This study summarizes the possibilities offered nowadays by commercial TPSs, highlighting the absence of some useful tools that would notably improve the planning of MR-based interstitial component cervix brachytherapy.

Clinical outcome of combined intracavitary / interstitial brachytherapy using a hybrid applicator in locally advanced cervical cancer

OBJECTIVE

The aim of this study was to evaluate the clinical outcome in locally advanced cervical cancer (LACC) after image-guided adaptive brachytherapy (IGABT) with combined intracavitary and interstitial (IC/IS) techniques using the hybrid Venezia applicator (Elekta AB, Sweden).

METHODS

LACC patients (UICC Stage IIB - IVB) treated with radiochemotherapy followed by IGABT with the hybrid IC/IS Venezia applicator at a single institution were retrospectively analyzed. Treatment comprised EBRT of the pelvis with 45 Gy and concomitant weekly cisplatin chemotherapy (40 mg/m²) followed by MRI-based IGABT. Dosimetry, oncological outcome and toxicity were investigated.

RESULTS

Forty-six patients underwent a total of 184 fractions of IGABT between 2017 and 2020. Median follow-up was 24 months. Combined IC/IS techniques were used in 40 patients (87%). The median HRCTV volume was 31.2 cm³ and the median HRCTV D_90% was 92.3 Gy (EQD2₁₀). The median D_2cm³ was 74.8 Gy for bladder, 57.9 Gy for rectum, 60.0 Gy for sigmoid and 52.2 Gy for bowel (EQD2₃). The 3-yr actuarial rates were 97.6% for local control, 97.6% for pelvic control, 59.9% for distant metastasis-free survival and 81.6% for overall survival. The crude rate for G2 and G3 late toxicity was 21.7% and 4.3%.

CONCLUSIONS

IGABT with the hybrid Venezia applicator and a pronounced use of a combined IC/IS technique achieved high target doses, while maintaining low doses to organs at risk, leading to excellent local control and overall survival rates with acceptable toxicity.

AAPM Task Group Report 303 endorsed by the ABS: MRI Implementation in HDR Brachytherapy-Considerations from Simulation to Treatment

The Task Group (TG) on Magnetic Resonance Imaging (MRI) Implementation in High Dose Rate (HDR) Brachytherapy - Considerations from Simulation to Treatment, TG 303, was constituted by the American Association of Physicists in Medicine's (AAPM's) Science Council under the direction of the Therapy Physics Committee, the Brachytherapy Subcommittee, and the Working Group on Brachytherapy Clinical Applications. The TG was charged with developing recommendations for commissioning, clinical implementation, and on-going quality assurance (QA). Additionally, the TG was charged with describing HDR brachytherapy (BT) workflows and evaluating practical consideration that arise when implementing MR imaging. For brevity, the report is focused on the treatment of gynecologic and prostate cancer. The TG report provides an introduction and rationale for MRI implementation in BT, a review of previous publications on topics including available applicators, clinical trials, previously published BT related TG reports, and new image guided recommendations beyond CT based practices. The report describes MRI protocols and methodologies, including recommendations for the clinical implementation and logical considerations for MR imaging for HDR BT. Given the evolution from prescriptive to risk-based QA,¹ an example of a risk-based analysis using MRI-based, prostate HDR BT is presented. In summary, the TG report is intended to provide clear and comprehensive guidelines and recommendations for commissioning, clinical implementation, and QA for MRI-based HDR BT that may be utilized by the medical physics community to streamline this process. This report is endorsed by the American Brachytherapy Society (ABS). This article is protected by copyright. All rights reserved.

Large volume was associated with increased risk of acute non-hematologic adverse events in the hybrid of intracavitary and interstitial brachytherapy for locally advanced uterine cervical cancer: preliminary results of prospective phase I/II clinical trial

OBJECTIVE

This is the preliminary results of a multi-center prospective clinical trial evaluating the feasibility of the hybrid of intracavitary and interstitial brachytherapy for locally advanced cervical cancer.

METHODS

Patients with FIGO stage IB2, IIA2, IIB, IIIA, IIIB and IVA uterine cervical cancer pretreatment width of which was ≥5 cm measured by MRI were eligible. Protocol therapy consisted of 30-30.6 Gy in 15-17 fractions of whole pelvic radiotherapy concurrent with weekly CDDP, followed by 24 Gy in 4 fractions of hybrid of intracavitary and interstitial and pelvic radiotherapy with central shield up to 50-50.4 Gy in 25-28 fractions. The primary endpoint of phase I part was that the rate of grade ≥ 3 acute non-hematologic adverse events related to hybrid of intracavitary and interstitial would be <10%.

RESULTS

Between October 2015 and October 2019, 74 patients underwent primary registration, with 52 patients eventually proceeding to the secondary registration. The median pretreatment tumor width was 5.7 cm, and FIGO Stages were IB2 10, IIA2 2, IIB 20 and IIIB 20, respectively. The median high-risk clinical target volume D90 was 72.0 Gy (54.8-86.6 Gy, EQD2), rectum D2cc was 53.7 Gy (29.3-80.3 Gy) and bladder D2cc was 69.8 Gy (38.9-84.8 Gy). The rate of grade ≥ 3 non-hematologic adverse events related to hybrid of intracavitary and interstitial was 1.9% (1/52), and 17.3% (9/52) of patients experienced non-hematologic adverse events related to hybrid of intracavitary and interstitial of any grade. In multivariate analysis, high-risk clinical target volume ≥ 35 ml was associated with an increased risk of any grade of acute non-hematologic adverse events related to hybrid of intracavitary and interstitial (P = 0.036).

CONCLUSION

The feasibility and reproducibility of hybrid of intracavitary and interstitial were demonstrated from a multi-center prospective clinical trial.

High-Dose-Rate Interstitial Brachytherapy for Deeply Situated Gynecologic Tumors Guided by Combination of Transrectal and Transabdominal Ultrasonography: A Technical Note

Background and Purpose

High-dose-rate interstitial brachytherapy (HDR-ISBT) is recommended to obtain a better local tumor control for uterine cancer patients in specific situations such as bulky lesions, an extension to the lateral parametrium, or tumors with irregular shapes. Our group uses real-time transrectal ultrasonography (TRUS) to guide freehand interstitial needle insertion. Occasionally, target tumors locate deeper beyond the rectum and cannot be visualized by TRUS. CT can guide needles to deeply located tumors, but in such cases, repeated image obtainment is required to achieve ideal needle localization. In this report, we present nine cases of patients who underwent HDR-ISBT for deeply situated tumors guided by a combination of transrectal and transabdominal ultrasonography (TR/TA-US).

Material and Methods

Nine uterine cancer patients whose tumors were located deeper than the reach of TRUS and underwent HDR-ISBT guided by TR/TA-US were presented. All nine cases had no distal organ metastasis and underwent external beam radiation therapy (EBRT) to the pelvic region for 45–50.4 Gy in 25–28 fractions followed by boost HDR-ISBT for deeply situated tumors guided by TR/TA-US.

Results

There were seven cervical cancer and two endometrial cancer patients: six with extensive uterine corpus invasion, one cervical cancer with massive pelvic lymph node metastasis, one cervical cancer with postoperative pelvic recurrence, and one with left ovarian direct tumor invasion. The median follow-up period was 15 months (range 3–28 months). The average clinical target volume at the time of first HDR-ISBT was 131 ml (range 44–335 ml). The linear distance from the vaginal entrance to the deepest part of the tumor at first time brachytherapy of nine cases was 14.0 (9.0–17.0) cm. HDR-ISBT dose fractionation was 24–30 Gy in four or five fractions. Seven out of nine cases had no local recurrence in the follow-up period. One had local in-field recurrence 25 months after HDR-ISBT. Another case with carcinosarcoma could not obtain local control and underwent salvage hysterectomy for a residual uterine tumor 11 months after HDR-ISBT. Four cases had extra-field recurrence in lymph nodes or distant organs.

Conclusions

In brachytherapy for gynecologic malignancies, deeply situated tumors located out of reach of TRUS may obtain favorable local control by HDR-ISBT guided with TR/TA-US.

Combined Interstitial and Intracavitary High-Dose Rate Brachytherapy of Cervical Cancer

High-dose-rate brachytherapy by remote afterloading is now performed under three-dimensional image guidance by CT or MRI. Three-dimensional image-guided brachytherapy in cervical cancer disclosed that the traditional intracavitary brachytherapy by Manchester method cannot deliver an adequate dose to the large tumor with resulting local recurrence. To improve the local control rate, combined interstitial and intracavitary (hybrid) brachytherapy can increase the dose to the large parametrial involvement without increasing the dose to the rectum and bladder. Whether hybrid brachytherapy can be performed safely on a multi-institutional basis remains to be studied. From 2015, phase I/II study of hybrid brachytherapy was launched in Japan, and it was revealed that hybrid brachytherapy can be performed safely and with a high quality of radiation dose distribution in a multi-institutional study. In Japan, the number of patients undergoing hybrid brachytherapy in cervical cancer is rapidly rising. Education and clinical trial are very important to establish hybrid brachytherapy in the management of cervical cancer.

Dosimetric comparison of high-dose rate cervix brachytherapy with and without interstitial needles and the impact on target volume coverage, and organ at risk constraints

INTRODUCTION

The aim of this audit was to compare the data from the Wellington Blood and Cancer Centre (WBCC) with international reported experience by quantifying the dosimetric impact of interstitial needles on target coverage and organ at risk (OAR) doses.

METHODS

All patients identified as having had interstitial needles as part of their treatment out of a cohort of 120 radically treated cervical cancer patients between 2013 and 2019 were included. Each patient acted as their own control with two treatment plans optimised for each fraction; the clinically treated plan and a re-optimisation without the use of interstitial needles. Plan optimisation was completed according to the departmental protocol and cumulative equivalent doses for 2 Gy fractions (EQD2) were calculated.

RESULTS

Eighteen patients were suitable for evaluation. A total of 52 insertions with interstitial needles were performed, of the 148 needles inserted, 119 (80.4%) were loaded. HRCTV D90% coverage mean was EQD2 5.4 Gy (0.5-10.6 Gy) higher for the course containing loaded interstitial needles, while no significant change was observed with regards to OAR doses. This improved coverage is in line with international standards which report 4.4-9.0 Gy.

CONCLUSION

WBCC's early experience of interstitial cervix brachytherapy has shown our target coverage improvements meet previously published international standards and confirms the value of this technique. This audit supports ongoing use of interstitial needles at the WBCC.

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.

Practical needle selection for Vienna-style applicators: improving therapeutic ratio in hybrid intracavitary-interstitial brachytherapy

Purpose

Hybrid intracavitary and interstitial (IC/IS) applicators improve dose distribution compared to traditional IC applicators in cervical high-dose-rate (HDR) brachytherapy. There is a learning curve to these applicators, and initial standard needle insertion patterns have not been well-established. In this study, we quantified dosimetric benefits of IC/IS applicators, and offer practical initial interstitial needle-selection, insertion depths, and dwell position recommendations.

Material and methods

Fifteen patients previously treated with a tandem and ring IC applicator and magnetic resonance (MR)-guidance were re-planned at first fraction using a digital template of Vienna-style interstitial needles. IC/IS plans maintained identical high-risk clinical target volume (HR-CTV) D_90% while reducing dose to organs at risk (OARs). To assess the validity of planning using virtual needles, virtual needle templates were overlaid on twelve clinical IC/IS plans, and the displacements between 40 physical and virtual needles were measured at 3 cm depth.

Results

The median HR-CTV volume in the present study was 19.6 cc (range, 6.6-60.5 cc). HR-CTV D_90% was maintained in all re-plans. Median bladder D_2cc decreased from 5.4 Gy per fraction to 4.8 Gy (p = 0.003); median rectum D_2cc decreased from 2.4 Gy per fraction to 2.0 Gy (p = 0.007). We suggest that a standard loading pattern should include needles in lateral channels 4, 5, and 9, 10 inserted 3 cm deep, with dwell times < 20% of the combined tandem and ring dwells. The mean displacement between planned and physical needles was 1.8 mm. All needles but three deviated less than 3.3 mm, demonstrating the validity of re-planning with virtual needles.

Conclusions

Hybrid IC/IS applicators maintain excellent D_90% coverage while improving dose to OARs compared to IC-only applicators, even in non-bulky HR-CTVs. We offer practical recommendations for needle selection, insertion depth, and relative weighting for Vienna-style applicators in small HR-CTVs. These results support previous publications, offering practical recommendations for users of Vienna-style hybrid applicators.

Knowledge-based dose prediction models to inform gynecologic brachytherapy needle supplementation for locally advanced cervical cancer

PURPOSE

The use of interstitial needles, combined with intracavitary applicators, enables customized dose distributions and is beneficial for complex cases, but increases procedure time. Overall, applicator selection is not standardized and depends on physician expertise and preference. The purpose of this study is to determine whether dose prediction models can guide needle supplementation decision-making for cervical cancer.

MATERIALS AND METHODS

Intracavitary knowledge-based models for organ-at-risk (OAR) dose estimation were trained and validated for tandem-and-ring/ovoids (T&R/T&O) implants. Models were applied to hybrid cases with 1-3 implanted needles to predict OAR dose without needles. As a reference, 70/67 hybrid T&R/T&O cases were replanned without needles, following a standardized procedure guided by dose predictions. If a replanned dose exceeded the dose objective, the case was categorized as requiring needles. Receiver operating characteristic (ROC) curves of needle classification accuracy were generated. Optimal classification thresholds were determined from the Youden Index.

RESULTS

Needle supplementation reduced dose to OARs. However, 67%/39% of replans for T&R/T&O met all dose constraints without needles. The ROC for T&R/T&O models had an area-under-curve of 0.89/0.86, proving high classification accuracy. The optimal threshold of 99%/101% of the dose limit for T&R/T&O resulted in classification sensitivity and specificity of 78%/86% and 85%/78%.

CONCLUSIONS

Needle supplementation reduced OAR dose for most cases but was not always required to meet standard dose objectives, particularly for T&R cases. Our knowledge-based dose prediction model accurately identified cases that could have met constraints without needle supplementation, suggesting that such models may be beneficial for applicator selection.

Morbidity following image-guided brachytherapy for cervical cancer: Patient and treatment related factors

PURPOSE

This retrospective study aims to assess factors associated with the occurrence of toxicity after brachytherapy (BT), as boost after external beam radiotherapy (EBRT) for treatment of invasive cervix carcinoma.

METHODS AND MATERIALS

All consecutive patients diagnosed with cervical carcinoma, and treated with concurrent radiochemotherapy from August 2017 to January 2020 were retrospectively included. An isodose conformation index (ICI) was developed to assess the percentage of the prescription isodose contained within the intermediate risk clinical target volume (IR-CTV).

RESULTS

Eighty-one patients with invasive cervix carcinoma from stage IB to stage IVa were included. Thirty-two (40%) and 49 (60%) patients were treated with Pulsed Dose Rate (PDR) and High Dose Rate (HDR) BT, respectively. Median follow-up was 19.6 months (5.6-41.2). The main factors associated with development of gastrointestinal toxicity were: the median volume of the prescription isodose (67.9cm[3] [37.6-92.9] vs. 49.1cm[3] [34.5-53.5], p = 0.05), the value of ICI (59% [51%-83%] vs. 86% [65%-96%], p = 0.01), the median equivalent dose delivered to the sigmoid (D2cc= 58.4 GyEQD2 [53.9-61.1] vs. 55.2 GyEQD2 [52.8-57.5], p = 0.06) and the median equivalent dose delivered to the IR-CTV (D90= 63.9 GyEQD2 [60.6-66.4] vs. 61.2 GyEQD2 [59.4-64.5], p = 0.03). The proportion of patients who received EBRT lymph node boost was higher in patients who developed urinary toxicity than in patients who did not (57.1% vs. 28.6%, p = 0.08). Anticoagulant (p = 0.02) and antiaggregant therapy (p = 0.01) were associated with occurrence of both urinary and gastrointestinal toxicity.

CONCLUSIONS

Our study confirms the predictive value of irradiated volume in the occurrence of gastrointestinal toxicity, as well as the need for a better conformation to the target volume. Precautions should be considered in patients with vascular comorbidities.

Selection of brachytherapy applicators based on tumor size and shape for cervical cancer: simulation analysis of pear-shaped isodose dimensions

The purpose of study is to measure Point A pear-shaped isodose dimensions of the conventional intracavitary brachytherapy with various sizes of colpostats and analyze which size of tumor is the optimal for 3-D interstitial brachytherapy. CT simulation was performed with Fletcher type applicator using various sizes of colpostats (2.0, 2.5, and 3.0 cm diameter). The Manchester standard loading (dwell time) system was used to generate pear-shaped isodose envelopes with high-dose rate iridium-192 according to the colpostat sizes. The size of the pear-shaped envelope was measured at 5 different levels: A-level (center of the colpostats), B-level (top of the colpostats), C-level (between B and D), D-level (Point A), and E-level (1.0 cm above Point A). In this study, it was assumed that uterine tandem was located at the center of tumor. For width of pear-shape: At the A-level, 6.4, 7.3, and 8.0 cm for 2.0, 2.5, and 3.0 cm colpostats, respectively. At the B-level, 5.8, 6.4, and 6.8 cm for 2, 2.5, and 3.0 cm colpostats, respectively. At the C-level, 4.6, 4.8, and 4.8 for 2.0, 2.5, and 3.0 cm colpostats, respectively. At the D-level, 4.0 cm for all different size. At the E-level, 3.8 cm for all 3 different size colpostats. A-level was the largest dimension of pear-shape. However, it was located in the upper vagina below the main cervical mass. The center of the effective pear-shape size for tumor was between the C and D levels. For thickness, all 5 different levels were ranging 3.7 to 4.0 cm. For height, the length of height was dependent on the tandem length. Therefore, the pear-shape envelope was able to accommodate up to 4.0 cm diameter volume. According to our analysis of conventional pear-shape dimension, 3-D interstitial brachytherapy should be considered for tumors larger than 4.0 cm for symmetrical tumor.

Advances in management of locally advanced cervical cancer

Globally, cervical cancer has the fourth highest cancer incidence and mortality in women. Cervical cancer is unique because it has effective prevention, screening, and treatment options. This review discusses the current cervical cancer advances with a focus on locally advanced cervical cancer. Topics discussed include diagnostic imaging principles, surgical management with adjuvant therapy and definitive concurrent chemoradiotherapy. Emphasis is given on current advances and future research directions in radiation therapy (RT) with an emphasis on three-dimensional brachytherapy, intensity-modulated RT, image-guided RT, proton RT and hyperthermia.

[Dose optimization in 3D pulsed dose rate brachytherapy for patients with locally advanced cervical cancer: A French multicenter phase II trial]

PURPOSE

We present the results of the PHRC Tridicol, a prospective French phase II study whose objective was to increase the dose delivered to the target volume during brachytherapy for locally advanced cervical cancers.

MATERIAL AND METHODS

Eight centers included 48 patients, treated with concomitant radiochemotherapy, then uterovaginal brachytherapy.

RESULTS

The median follow-up was 63 months. The dose of brachytherapy delivered in biological equivalent dose (EQD2) to 90% of the High Risk CTV (D90 CTV HR) was 80Gy in median dose. The 5-year local control rate (LC) was 84%, close to the hypothesis of 86.7%. The rate of severe complications (grade 3-4) was 23% at 5 years. The rectal dose was correlated with the risk of severe complications.

CONCLUSION

HR CTV dose was below the target (85Gy) due to low use of parametrial interstitial needles, as the centers did not always have an adequate applicator, or were at the time at the beginning of their learning curve. The 5-year LC rate was improved compared to that of the comparable STIC PDR group (78%) but lower than the retroEMBRACE cohort of GEC ESTRO (89%). The complication rate was higher than in the comparable group of STIC PDR but close to that of retroEMBRACE. Training brachytherapy teams in interstitial implantation or referring patients to referral centers should help improve the therapeutic index of cervical cancer.

Characterization of combined intracavitary/interstitial brachytherapy including oblique needles in locally advanced cervix cancer

PURPOSE

To characterize and report on dosimetric outcomes of image guided adaptive brachytherapy (IGABT) using intracavitary and interstitial (IC/IS) applicators including oblique needles (O-needles) in locally advanced cervical cancer (LACC).

METHODS AND MATERIALS

Twenty LACC patients treated with radio-chemotherapy and offered IC/IS-IGABT including O-needles were analyzed. An in-house 3D-printed vaginal template was used to steer the needles parallel and obliquely in relation to the tandem, supplemented with free-hand needles if needed. Implant characteristics and loading patterns were analyzed. Using the equivalent dose in 2Gy-fractions (EQD2) concept, cumulative (EBRT+BT) V85, V75, V60Gy, targets/OARs doses and high dose volumes (150%, 200% and 300% (100% = 85 Gy EQD2₁₀)) were evaluated.

RESULTS

Median(range) tumor width at diagnosis was 5.5(3.6; 7.5)cm; CTV_HR volume was 45(23; 136)cm³ with maximum distance from tandem to CTV_HR border of 3.4(2.5; 4.8)cm. T-stage distribution was IIB/III/IVA in 6(30%)/9(45%)/5(25%) of patients. At BT, 13(65%) patients had distal parametrial/pelvic wall infiltration. Median(range) number of needles per patient was 11(8-18). Average distribution of intrauterine, vaginal and interstitial dwell times were 31%, 25% and 44%, respectively. Median(range) dwell-time per dwell position was 11(2-127)% of average point-A based standard loading. Median V_85Gy/V_150%/V_200%/V_300% were 85(38; 171)/41(21; 93)/22(12; 41)/7(4; 19) cm³; CTV_HR D_90% was 93(83; 97)Gy EQD2₁₀; bladder/rectum/sigmoid/bowel D_2cm3 were 78(64; 104)/65(52; 76)/59(53; 69)/61(47; 76)Gy EQD2₃.

CONCLUSIONS

The use of O-needles in patients with large and/or unfavorable tumors resulted in excellent target coverage and OARs sparing. Intrauterine and vaginal loadings were reduced compared to standard loading and almost half of the loading was shifted into IS needles. This was achieved with gentle loading in the majority of dwell positions.

Non-anesthetist-administered moderate sedation with midazolam and fentanyl for outpatient MRI-aided hybrid intracavitary and interstitial brachytherapy in cervix cancer: a single-institution experience

Purpose

The aim of the study was to determine the feasibility of interstitial brachytherapy under non-anesthetist-administered moderate sedation, to identify factors influencing the insertion, and the total procedural time.

Material and methods

A total of 47 insertions with hybrid intracavitary and interstitial applicators were performed in 23 patients from March 2017 to March 2020. Moderate sedation was achieved with intravenous midazolam and fentanyl administered by non-anesthetist. Insertion time and procedural time was recorded. Univariate and multivariate analysis were performed to evaluate the impact of different factors on insertion and procedural time.

Results

A total of 238 needles (range, 2-8 per insertion) were implanted, with an average insertion depth of 30 mm (range, 20-40 mm). The mean doses for midazolam and fentanyl were 3 mg (standard deviation [SD] = 1) and 53.3 mcg (SD = 23.9) per insertion, respectively. The median insertion time was 30 minutes (interquartile range [IQR] = 22-40), and the median total procedural time was 4.3 hours (IQR = 3.6-5.2). First time insertion, insertions performed before 2019, and higher midazolam dose were associated with significantly longer insertion time, whereas longer insertion time, MRI-based planning, and insertions performed before 2019 were associated with significantly longer total procedural time.

Conclusions

Outpatient interstitial brachytherapy with non-anesthetist-administered sedation is achievable and well-tolerated. This method may significantly lessen the burden on hospital resources and has the potential to be cost-effective.

Hybrid tandem and ovoids brachytherapy in locally advanced cervical cancer: impact of dose and tumor volume metrics on outcomes

PURPOSE

To report the impact of dose and tumor volume metrics at brachytherapy on outcomes for locally advanced cervical cancer treated with tandem and ovoids intracavitary/interstitial brachytherapy.

MATERIAL AND METHODS

FIGO stage IB1-IIIB locally advanced cervical cancer treated with intracavitary/interstitial brachytherapy via a tandem and ovoids hybrid applicator were analyzed. Median high-risk clinical target volume (HR-CTV), rate of tumor volume reduction, EQD2 D90, organ at risk doses, and outcomes were recorded. Univariable and multivariable Cox regression was applied for survival analysis, and logistic regression was used for toxicity analysis.

RESULTS

Seventy-one patients were identified. Median follow-up was 24.9 months, with a 2-year local control of 83.6%, loco-regional control of 72.0%, and overall survival of 88.6%. Median HR-CTV D90 was 87.4 Gy (IQR = 85.7-90.2). Median HR-CTV D90 > 90 Gy10 showed a trend toward improved local control (LC) (p = 0.19). Median HR-CTV was 37.9 cm3, and median V100 was 86.5%. A median HR-CTV of ≥ 40 cm3 demonstrated worse loco-regional control (LRC) (p = 0.018) and progression-free survival (p = 0.021). Two-year LC and LRC for stage IIB patients with a median HR-CTV < 40 cm3 were significantly improved as compared to ≥ 40 cm3 at 100% and 71.8%, respectively (p = 0.019) and 100% and 56.5%, respectively (p = 0.001). However, this trend was not statistically significant for stage IIIB patients. Higher percent per day reduction in HR-CTV during brachytherapy showed improved LRC (p = 0.045). Four percent of patients experienced acute grade 3 genitourinary toxicity, 1% late grade 3 genitourinary and 1% late grade 3 gastrointestinal toxicity.

CONCLUSIONS

Tandem and ovoids intracavitary/interstitial brachytherapy provides satisfactory outcomes with modest toxicity. Higher HR-CTV D90 coverage demonstrated a trend toward improved tumor control. Tumor volume based on median HR-CTV ≥ 40 cm3 at brachytherapy was prognostic for poor outcomes, even within initial FIGO stage groups warranting caution.

Development of a Machine Learning Model for Optimal Applicator Selection in High-Dose-Rate Cervical Brachytherapy

Purpose

To develop and validate a preliminary machine learning (ML) model aiding in the selection of intracavitary (IC) versus hybrid interstitial (IS) applicators for high-dose-rate (HDR) cervical brachytherapy.

Methods

From a dataset of 233 treatments using IC or IS applicators, a set of geometric features of the structure set were extracted, including the volumes of OARs (bladder, rectum, sigmoid colon) and HR-CTV, proximity of OARs to the HR-CTV, mean and maximum lateral and vertical HR-CTV extent, and offset of the HR-CTV centre-of-mass from the applicator tandem axis. Feature selection using an ANOVA F-test and mutual information removed uninformative features from this set. Twelve classification algorithms were trained and tested over 100 iterations to determine the highest performing individual models through nested 5-fold cross-validation. Three models with the highest accuracy were combined using soft voting to form the final model. This model was trained and tested over 1,000 iterations, during which the relative importance of each feature in the applicator selection process was determined.

Results

Feature selection indicated that the mean and maximum lateral and vertical extent, volume, and axis offset of the HR-CTV were the most informative features and were thus provided to the ML models. Relative feature importances indicated that the HR-CTV volume and mean lateral extent were most important for applicator selection. From the comparison of the individual classification algorithms, it was found that the highest performing algorithms were tree-based ensemble methods – AdaBoost Classifier (ABC), Gradient Boosting Classifier (GBC), and Random Forest Classifier (RFC). The accuracy of the individual models was compared to the voting model for 100 iterations (ABC = 91.6 ± 3.1%, GBC = 90.4 ± 4.1%, RFC = 89.5 ± 4.0%, Voting Model = 92.2 ± 1.8%) and the voting model was found to have superior accuracy. Over the final 1,000 evaluation iterations, the final voting model demonstrated a high predictive accuracy (91.5 ± 0.9%) and F1 Score (90.6 ± 1.1%).

Conclusion

The presented model demonstrates high discriminative performance, highlighting the potential for utilization in informing applicator selection prospectively following further clinical validation.

Evaluation of exit skin dose for intra-cavitary brachytherapy treatments by the BEBIG 60Co machine using thermoluminescent dosimeters

Purpose:

This study aims to evaluate the application of the exit skin dose (ESD) in verifying the accuracy of intra-cavitary brachytherapy treatments performed by the BEBIG 60Co machine using thermoluminescent dosimeters (TLDs).

Materials and methods:

Eleven patients who were treated for gynaecological (GYN) malignancy by high-dose-rate (HDR) brachytherapy machine have been considered in this study. A combination of tandem, cylinder and interstitial needles was applied for eight patients while tandem ovoid (TO) applicators were used for the rest (three patients). In order to measure ESD, thermoluminescent dosimetry was performed for each patient. TLDs were placed precisely on the patient’s skin along her symphysis pubis bone (anterior) and left (L)/right (R) sides of her pelvic. Positioning of the dosimeter was accurately determined using fiducial markers in computed tomography (CT) scan imaging, prior to the treatment. Finally, a comparison was made between the calculated dose from the treatment planning system (TPS) and the dose measured by TLDs.

Results:

About 90% of all cases showed a good agreement (while considering TLD uncertainty ∼5·5%) between TPS dose calculations and TLD measurements. The measured mean values of ESD received to anterior, left and right positions were 56·72, 12·18 and 12·82 cGy, respectively. For three patients, differences up to 11·9% were detected.

Conclusion:

To conclude, ESD measurement method can be a suitable practical approach for verifying the accuracy of GYN HDR treatment delivery.

Intracavitary/Interstitial Applicator Plus Distal Parametrial Free Needle Interstitial Brachytherapy in Locally Advanced Cervical Cancer: A Dosimetric Study

Purpose

To explore the dosimetric advantage of combining intracavitary/interstitial applicator with distal parametrial free needle interstitial brachytherapy (IC/IS+ISBT DP) based on MRI for locally advanced cervical cancer.

Methods and Materials

77 IC/IS+ISBT DP treatment plans were developed for 34 patients with locally advanced cervical cancer from June 2016 to January 2020 in this study. We removed the free needles and devised a new IC/ISBT treatment plan based on the same principle. We then compared the dosimetric differences of D90, D98, V100, V150, V200 for HR-CTV (high-risk clinical target volume), D90 for IR-CTV (Intermediate risk-CTV) and D2cc for OARs (organs at risk) between the two groups of treatment plans for the same patient, and the paired T test was performed in parallel. Further, the dosage differences between the two group plans under different parametrial extension widths (the maximum distance of HR-CTV from the vertical direction of the uterine tandem at coronal position) were compared. The survival rate was calculated using the Kaplan-Meier method. Prognostic factors for overall survival (OS) and progression-free survival (PFS) were determined by Cox regression method. RTOG/EORTC criteria were used to grade toxicities.

Results

A total of 297 free needles were used, with a weight ratio of 15.8% ± 0.11, and a mean insertion depth of 6.52cm ± 2.8cm. D90, D98, V100 for HR-CTV, and D90 for IR-CTV for IC/IS+ISBT DP were significantly higher than IC/ISBT for which free needles were removed (p<0.05). And the V200 for HR-CTV and D2cc for bladder, rectum and sigmoid were decreased (p<0.05). When the parametrial extension widths were greater than 3cm, the HR-CTV D90 and the D2CC for rectum, bladder and sigmoid colon for IC/IS-ISBT DP were advantageous compared to IC/ISBT (p<0.05). The 2-yr OS, PFS and local control rate (LC) were 82.3, 66.8, and 93.1%, respectively. Parametrial extension widths was the only statistically prognostic factors for PFS (p = 0.002) on univariate analysis. No grade 3 or 4 Treatment-related toxicities were observed.

Conclusion

Our institutional experiences showed that IC/IS+ISBT DP is an effective treatment for cervical cancer patients with distal parametrial extension. IC/IS-ISBT DP had dosage advantage and clinical feasibility in locally advanced cervical cancer with distal parametrial extension when the parametrial extension widths were greater than 3cm.

Venezia applicator with oblique needles improves clinical target volume coverage in distal parametrial tumor residue compared to parallel needles only

Purpose

Residual distal parametrial involvement after radiochemotherapy is a true challenge for brachytherapists since the width and asymmetry of high-risk clinical target volume (HR-CTV) are difficult to cover properly with a standard implant.

Material and methods

Dosimetric plans of five patients treated with Venezia advanced gynecological applicator at our institution were reviewed. For each patient, we compared the original plan with a new plan where oblique needles were removed and re-optimized manually. Optimization process was halted when EQD2₁₀ D₉₀ HR-CTV reached 90 Gy, when one hard constraint to organs at risk (OARs) was reached according to the EMBRACE II protocol, or when dose-rate of one of OARs exceeded 0.6 Gy/h.

Results

Tumors were large; median HR-CTV volume was 64 cc and median distance between tandem and outer contour of HR-CTV was 40 mm. For the five patients, HR-CTV EQD2₁₀ D₉₀ was superior in the plan using oblique needles, with a median difference of 6.5 Gy (range, 1.7-8.5 Gy). Median D₉₀ HR-CTV and intermediate-risk CTV (IR-CTV) were significantly increased with oblique needles: 85.9 Gy (range, 83.2-90.3 Gy) vs. 81.5 Gy (range, 77.4-84 Gy), and 68.7 Gy (range, 66.3-72.3 Gy) vs. 67 Gy (range, 64.3-69.1 Gy), p = 0.006 for both. There were no significant differences in the dose to OARs. Plans with only parallel needles had less favorable dose distribution, with cold spots on the outer parametria and higher vaginal activation to compensate parametrial coverage in its inferior part.

Conclusions

Venezia^TM applicator permits reproducible application to increase CTV coverage in patients with distal parametrial tumor residue during brachytherapy, while maintaining acceptable dose to OARs.

Computed Tomography-Guided Optimization of Needle Insertion for Combined Intracavitary/Interstitial Brachytherapy With Utrecht Applicator in Locally Advanced Cervical Cancer

PURPOSE

There are no international guidelines for optimal needle insertion during interstitial intracavitary brachytherapy (IS-ICBT) for cervical cancer. We aimed to investigate the clinical feasibility and added value of computed tomography (CT) guidance to optimize needle insertion in IS-ICBT using the Utrecht applicator and to evaluate needle shifts.

METHODS AND MATERIALS

We enrolled 24 patients who were treated with interstitial-brachytherapy. Two CT scans each were performed for every patient: (1) after applicator insertion without needles (CT_preneedle) and (2) after needle insertion (CT_postneedle). In addition to magnetic resonance imaging after external-beam radiation therapy, CT_preneedle was used to determine optimal needle locations and insertion lengths based on applicator and organs at risk positioning on the day of treatment; CT_postneedle was used for IS-ICBT planning. The needle-channel axis was used as a reference to determine needle-shift evolution.

RESULTS

A total of 266 interstitial needles were inserted in 76 of 93 BT fractions with high intra- and interpatient variations in the number of inserted needles. Based on CT_preneedle findings, needle insertion was avoided in 9, 4, 2, and 2 patients at the first, second, third, and fourth fractions, respectively. The unloaded needle frequency was 4%. Average needle contribution to total dwell time was 37.2% ± 19.2%. Shifting was observed in 68% of the needles (mean shift 2.0 ± 2.3 mm), mostly in the posterior direction, and in needles with a larger insertion length. Needle reinsertion was not needed in any patient. No complication due to needle insertion was observed, except for minor vaginal bleeding in 1 patient after needle removal.

CONCLUSIONS

The adaptive CT-guided IS-ICBT application was feasible and resulted in fewer unloaded needle insertions or complications and more efficient use with higher needle contribution to the treatment. Needle shift was frequent but did not require needle reinsertion with the proposed method.

Predictive value of Excel forms based on an automatic calculation of dose equivalent in 2 Gy per fraction in adaptive brachytherapy for cervical cancer

Purpose

External beam radiotherapy (EBRT) combined with brachytherapy (BT) is the standard mode of radical radiotherapy for locally advanced cervical cancer. The cumulative equivalent doses in 2 Gy per fraction (EQD₂) is an important basis for estimating the probability of local control of tumors and monitoring the occurrence of side effects in normal tissues. The purpose of this study was to explore the predictive value of Excel forms based on an automatic calculation in radical adaptive BT for cervical cancer.

Material and methods

A retrospective analysis of 119 patients suffering from cervical cancer, treated with radical radiotherapy. All patients were treated with EBRT and adaptive BT. EBRT prescribed dose was 42.0-50.4 Gy in 21-28 fractions. BT nominal prescribed dose was 28 Gy in 4 fractions, separated by one week. Total EQD₂ prediction at nth (n = 1-3) BT (TEPB_n) or actual cumulative EQD₂ (ACEQD₂) can be calculated automatically by inputting the physical dose based on an in-house designed application. The relationship between TEPB_n and ACEQD₂ was evaluated, and the predictive value of Excel forms based on the automatic calculation was analyzed.

Results

For the volume of high-risk clinical target, there was a significant decrease between BT1 and BT2. Similarly, for the volume of intermediate-risk clinical target, there was a significant decrease between BT2 and BT3. The sensitivity ranges of TEPB₁, TEPB₂, and TEPB₃ prediction were 74.5-91.3%, 83.7-95.7%, and 92.9-99.1%, respectively, and the specificity ranges were 46.7-80.0%, 53.3-90.5%, and 66.7-90.5%, respectively.

Conclusions

The in-house designed application has the function of quickly reading dose-volume histogram (DVH) parameters from the treatment planning system, which allows for balance between the total dose to target volumes and organs at risk (OARs). Excel forms based on EQD₂ automatic calculation presents high predictive accuracy.

Three-dimensional image-guided combined intracavitary and interstitial high-dose-rate brachytherapy in cervical cancer: A systematic review

PURPOSE

To evaluate the local control and toxicities of three-dimensional image-guided combined intracavitary and interstitial (IC/IS) high-dose-rate brachytherapy (BT) in cervical cancer through a systematic review.

METHODS AND MATERIALS

A systematic review of relevant studies was performed through the PubMed, Web of Science, and Cochrane Library databases through May 10, 2020. Articles reporting on IC/IS technology, volumetric doses to high-risk clinical target volume (HR-CTV) and organs at risk (OARs), tumor control and/or treatment-related side effects were identified. The key information, including the type of applicator, implantation technology, characteristics of implantation, volumetric doses, tumor control, and/or treatment-related side effects, was extracted. A probit model analysis between HR-CTV D90 and tumor local control was performed.

RESULTS

Twelve studies encompassing 520 patients were included in the probit model between HR-CTV D90 and the local control rate. The probit model showed a significant relationship between the HR-CTV D90 value and the local control probability, p = 0.003. The prescribed dose of 85 Gy_EQD2,10 would in theory warrant an 87.4% (95% confidence interval 82.5%-90.5%) local control rate.

CONCLUSION

IC/IS BT is an appropriate method to achieve a high therapeutic ratio for tumors with large volumes or poor responses after external irradiation in cervical cancer. The probit model showed that the dose escalation of HR-CTV D90 was helpful to improve the local tumor control rate.

Modern development of high-dose-rate brachytherapy

Brachytherapy is an invasive therapy with placement of radiation source into or near the tumor. The difference between planning target volume and clinical target volume is minimal, and the dose out of the tumor reduces rapidly due to the inverse-square law. High-dose-rate brachytherapy enables three-dimensional image guidance, and currently, tumor dose as well as doses of the surrounding normal structures can be evaluated accurately. High-dose-rate brachytherapy is the utmost precision radiation therapy even surpassing carbon ion therapy. Biological disadvantages of high-dose rate have been overcome by the fractional irradiation. High-dose-rate brachytherapy is indispensable in the definitive radiation therapy of cervical cancer. Also in prostate cancer and breast cancer, high-dose-rate brachytherapy plays a significant role. Brachytherapy requires techniques and skills of radiation oncologists at the time of invasive placement of the radiation source into the tumor area. Education of young radiation oncologists is most urgent and important.

Analysis of clinical utilization of ring applicator for combined intracavitary/interstitial image-guided brachytherapy treatment in Chinese patients with locally advanced cervical cancer

Purpose

To analyze the results of clinical utilization of ring applicator for combined intracavitary (IC)/interstitial (IS) image-guided brachytherapy (BT) technique in locally advanced cervical cancer (LACC), and to explore the application conditions of IC/IS BT approach with this applicator for Chinese patients.

Material and methods

IC/IS BT was performed in total of 95 LACC patients, who already received external beam radiotherapy. In forty-three of these patients, utilization of ring applicator in brachytherapy was done, including IC/IS BT approach with ring applicator for 65 fractions. Clinically optimized IC/IS BT plan with ring applicator (IC/IS treatment) and additionally generated optimized plan without needle use (IC research) were designed, respectively. Dosage differences in target regions and organs at risk (OARs) were analyzed between both the plans. Four planes were selected in the longitudinal direction of uterine cervix and divided the 360° area around the tandem into eight equal sectors. Tumor target features and prescription dose distributions on different planes were described.

Results

The usage rate of ring applicator with most suitable ring diameter of 26 mm was 45.3% in Chinese cervical cancer patients. The high-risk clinical target volume (HR-CTV) D₉₀/D₉₈ and intermediate-risk CTV (IR-CTV) D₉₀/D₉₈ in IC/IS treatment were significantly higher than IC research. As compared with IC research plan, the D_{2.0 cm³} of bladder and rectum in IC/IS treatment were significantly lower (p < 0.05). There was no significant difference in D_{2.0 cm³} of sigmoid and small bowel between two plans. When the target volume was larger than 36 cm³, IC alone had an inadequate coverage of target.

Conclusions

Nearly half of Chinese patients with LACC could be treated with the ring applicator. The application conditions of IC/IS BT approach with ring applicator for Chinese patients were achieved. Combined IC/IS image-guided BT based on magnetic resonance imaging (MRI) planning is clinically feasible in Chinese patients.

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.

Outcomes of freehand interstitial brachytherapy in advanced gynecologic malignancies

PURPOSE

The purpose of the study is to present the first results of freehand interstitial brachytherapy (ISBT) used to treat patients with carcinoma of the cervix and the vagina.

METHODS AND MATERIALS

Patients diagnosed with carcinoma of the cervix or carcinoma of the vagina who were not suitable for intracavitary brachytherapy were treated with freehand ISBT. The implant was performed transperineally using C arm or transrectal ultrasound guidance. Patients received an external beam radiotherapy dose of 50 Gy in 25 fractions. The dose delivered by high-dose-rate ISBT was 18 Gy in three fractions, 6 Gy per fraction, 6 h apart. The brachytherapy dose volume parameters were analyzed after CT-based planning using GEC ESTRO image-guided brachytherapy-based guidelines.

RESULTS

From June 2018 till November 2018, 14 patients were treated with freehand ISBT. The mean dose received by 90% of the high-risk clinical target volume (D₉₀) was 82 Gy EQD2₁₀ for patients with carcinoma of the cervix and 80 Gy EQD2₁₀ for patients with carcinoma of the vagina_. The mean dose received by 2 cc volume of the bladder and rectum was 80 Gy EQD2₃ and 70 Gy EQD2₃ for patients with carcinoma of the cervix and 75 Gy EQD2₃ and 72 Gy EQD2₃ for patients with carcinoma of the vagina, respectively. The mean dose received by 2 cc of the sigmoid was 65 Gy EQD2₃ for cervical carcinoma and 58 Gy EQD2₃ for vaginal carcinoma, respectively. At a median followup of 14 months, 2 patients developed local recurrence. Two patients developed Grade 2 gastro intestinal toxicity, and 1 patient developed Grade 2 genitourinary toxicity. None of the patients developed Grade 3 or 4 toxicities.

CONCLUSION

A freehand interstitial implant is feasible in resource limited settings and provides acceptable local control with minimal acute toxicity.

Verification of needle guidance accuracy in pelvic phantom using registered ultrasound and MRI images for intracavitary/interstitial gynecologic brachytherapy

Purpose

In combined intracavitary/interstitial (IC/IS) gynecologic brachytherapy, trackers attached to interstitial needles of localize real-time needle trajectories, and intraoperative ultrasound (US) images provide updated anatomy information during needle insertions. To achieve an effective visualization and image guidance, real-time needle trajectories and US images can be unified in preoperative magnetic resonance imaging (MRI) image space together. This study evaluates the rigid registration accuracy between US images and MRI images as well as the registration accuracy between US images and real-time needle trajectories in a pelvic phantom.

Material and methods

A method for US probe calibration and accomplished rigid registration between MRI images and US images was proposed. An IC/IS applicator was designed. Micro electromagnetic sensor to track and localize real-time needle trajectories in 3D MRI image space was used. Marker validation to test the accuracy of US probe calibration and pelvic phantom validation to test the registration accuracy between US images and MRI images was conducted as well as and pelvic phantom study to verify the registration accuracy between real-time needle trajectories and needle trajectories in registered US images.

Results

US probe calibration accuracy was 0.80 ±0.23 mm (n = 60). Registration accuracy between US images and MRI images were 1.01 ±0.22 mm in the axial plane (n = 60) and 1.14 ±0.20 mm in the sagittal plane (n = 24). Registration accuracy between real-time needle trajectories and needle trajectories in registered US images were 1.25 ±0.31 mm (n = 40) and 1.61 ±0.28 degrees (n = 5), respectively.

Conclusions

In this study, we showed that under ideal conditions, rigid registration between MRI images and US images obtained high accuracy for real-time image guidance. Additionally, registered US images provided accurate image guidance during visual needle insertion in IC/IS gynecologic brachytherapy to achieve a combination of effective visualization and image guidance.

Ring Versus Ovoids and Intracavitary Versus Intracavitary-Interstitial Applicators in Cervical Cancer Brachytherapy: Results From the EMBRACE I Study

PURPOSE

The aim of this study was to investigate the influence of brachytherapy technique and applicator type on target dose, isodose surface volumes, and organ-at-risk (OAR) dose.

METHODS AND MATERIALS

Nine hundred two patients treated with tandem/ovoids (T&O) (n = 299) and tandem/ring (T&R) (n = 603) applicators from 16 EMBRACE centers were analyzed. Patients received external beam radiation therapy and magnetic resonance imaging guided brachytherapy with dose prescription according to departmental practice. Centers were divided into 4 groups, according to applicator/technique: Ovoids and ring centers treating mainly with the intracavitary (IC) technique and ovoids and ring centers treating routinely with the intracavitary/interstitial (IC/IS) technique. V85Gy EQD210, CTVHR D90% (EQD210), and bladder, rectum, sigmoid, and vaginal 5-mm lateral-point doses (EQD23) were evaluated among center groups. Differences between T&O and T&R were tested with multivariable analysis.

RESULTS

For similar point A doses, mean CTVHR D90% was 3.3 Gy higher and V85Gy was 23% lower for ring-IC compared with ovoids-IC centers (at median target volumes). Mean bladder/rectum doses (D2cm3 and ICRU-point) were 3.2 to 7.7 Gy smaller and vaginal 5-mm lateral-point was 19.6 Gy higher for ring-IC centers. Routine use of IC/IS technique resulted in increased target dose, whereas V85Gy was stable (T&R) or decreased (T&O); reduced bladder and rectum D2cm3 and bladder ICRU-point by 3.5 to 5.0 Gy for ovoids centers; and similar OAR doses for ring centers. CTVHR D90% was 2.8 Gy higher, bladder D2cm3 4.3 Gy lower, rectovaginal ICRU-point 4.8 Gy lower, and vagina 5-mm lateral-point 22.4 Gy higher for ring-IC/IS versus ovoids-IC/IS centers. The P values were <.002 for all comparisons. Equivalently, significant differences were derived from the multivariable analysis.

CONCLUSIONS

T&R-IC applicators have better target dose and dose conformity than T&O-IC in this representative patient cohort. IC applicators fail to cover large target volumes, whereas routine application of IC/IS improves target and OAR dose considerably. Patients treated with T&R show a more favorable therapeutic ratio when evaluating target, bladder/rectum doses, and V85Gy. A comprehensive view on technique/applicators should furthermore include practical considerations and clinical outcome.

Needle-free cervical cancer treatment using helical multishield intracavitary rotating shield brachytherapy with the 169 Yb Isotope

PURPOSE

To assess the capability of an intracavitary ¹⁶⁹ Yb-based helical multishield rotating shield brachytherapy (RSBT) delivery system to treat cervical cancer. The proposed RSBT delivery system contains a pair of 1.25 mm thick platinum partial shields with 45° and 180° emission angles, which travel in a helical pattern within the applicator.

METHODS

A helically threaded tandem applicator with a 45° tandem curvature containing a helically threaded catheter was designed. A 0.6 mm diameter ¹⁶⁹ Yb source with a length of 10.5 mm was simulated. A 37-patient treatment planning study, based on Monte Carlo dose calculations using MCNP5, was conducted with high-risk clinical target volumes (HR-CTVs) of 41.2-192.8 cm³ (average ± standard deviation of 79.9 ± 35.8 cm³ ). All patients were assumed to receive 25 fractions of 1.8 Gy of external beam radiation therapy (EBRT) before receiving 5 fractions of high-dose-rate brachytherapy (HDR-BT). For each patient, ¹⁹² Ir-based intracavitary (IC) HDR-BT, ¹⁹² Ir-based intracavitary/interstitial (IC/IS) HDR-BT using a hybrid applicator with eight IS needles, and ¹⁶⁹ Yb-based RSBT plans were generated.

RESULTS

For the IC, IC/IS, and RSBT treatment plans, 38%, 84%, and 86% of the plans, respectively, met the planning goal of an HR-CTV D₉₀ (minimum dose to hottest 90%) of 85 Gy_EQD2 (α/β = 10 Gy). Median (25th percentile, 75th percentile) treatment times for IC, IC/IS, and RSBT were 11.71 (6.62, 15.40) min, 68.00 (45.02, 80.02) min, and 25.30 (13.87, 35.39) min, respectively. ¹⁹² Ir activities ranging from 159.1-370 GBq (4.3-10 Ci) and ¹⁶⁹ Yb activities ranging from 429.2-999 GBq (11.6-27 Ci) were used, which correspond to the same clinical ranges of dose rates at 1 cm off-source-axis in water. Extra needle insertion and planning time beyond that needed for intracavitary-only approaches was accounted for in the IC/IS treatment time calculations.

CONCLUSION

¹⁶⁹ Yb-based RSBT for cervical cancer met the HR-CTV D₉₀ goal of 85 Gy in a greater percentage of the patients considered than IC/IS (86% vs 84%, respectively) and can reduce overall treatment time relative to IC/IS. ¹⁶⁹ Yb-based RSBT could be used to replace IC/IS in instances where IC/IS treatment is not available, especially in instances when HR-CTV volumes are ≥30 cm³ .

Individualized and inverse optimized needle configuration for combined intracavitary-interstitial brachytherapy in locally advanced cervical cancer

Objectives

The aim of this study is to address the limitation of combined intracavitary-interstitial (IC/IS) brachytherapy (BT) in locally advanced cervical cancer using standardized applicators and to determine the optimal dose distribution in patients with challenging tumors, innovative methods of customizing and optimizing the IS needle configuration for combined IC/IS BT are proposed and investigated.

Materials and Methods

A software module that could customize the IS needle configuration and subsequently generate the digital model of guiding template for three-dimensional printing was developed and integrated into our in-house treatment planning system for BT. The inverse optimization method based on the technique of mixed-integer linear programming was introduced to determine the needle tracks out of a candidate pool and dwell times at corresponding locations to best meet dose objectives. A treatment planning study was conducted to evaluate the feasibility and performance of the proposed methods.

Results

The workflow for combined IC/IS BT with customized and inverse optimized IS needle configuration was presented. Dosimetric results of the treatment planning study showed that sufficient target coverage could be obtained with the customized IS needle configuration for challenging cases. The proposed dose-based optimization method for IS needle configuration was feasible and effective. Improved target coverage and organ-at-risk sparing were achieved using the inverse planning method.

Conclusions

Using the proposed methods of customizing and optimizing the IS needle configuration, the limitation in the standardized design of combined IC/IS applicators can be addressed, and sufficient target coverage is obtained in cervical cancer patients with unfavorable tumor topography and/or extra lateral expansion.

Definitive radiotherapy consisting of whole pelvic radiotherapy with no central shielding and CT-based intracavitary brachytherapy for cervical cancer: feasibility, toxicity, and oncologic outcomes in Japanese patients

BACKGROUND

This prospective study investigated the feasibility, toxicity, and oncologic outcomes of definitive radiotherapy (RT) consisting of whole pelvic radiotherapy with no central shielding (noCS-WPRT) and CT-based intracavitary brachytherapy (ICBT) in Japanese patients with cervical cancer.

METHODS

Patients with cervical cancer of FIGO stages IB1-IVA were eligible. The treatment protocol consisted of noCS-WPRT of 45 Gy in 25 fractions and CT-based high dose-rate ICBT of 15 or 20 Gy in 3 or 4 fractions prescribed at point A. The prescribed ICBT dose was decreased if the manual dwell time/position optimization failed to meet organs-at-risk constraints. Graphical optimization and additional interstitial needles were not applied.

RESULTS

We enrolled 40 patients. FIGO stages were IB1: 11, IB2: 13, IIA2: 1, IIB: 11, IIIB: 3, and IVA: 1. Median (range) pretreatment tumor diameter was 47 (14-81) mm. Point A doses were decreased in 19 of 153 ICBT sessions (12%). The median follow-up duration was 33 months. The 2-year rates of pelvic control, local control (LC), and progression-free survival were 83%, 85%, and 75%, respectively. Pre-ICBT tumor diameter, high-risk clinical target volume (HR-CTV), total HR-CTV D90, and overall treatment time (OTT) significantly affected LC. Late adverse events (grade ≥ 3) were observed in 3 patients (2 in the bladder, 1 in the rectum).

CONCLUSIONS

Definitive RT consisting of noCS-WPRT and CT-based ICBT was feasible for Japanese patients with cervical cancer. To further improve LC, additional interstitial needles for patients with a large HR-CTV and shorter OTT should be considered.

Dose distribution of brachytherapy for locally advanced (stage IIB) cervical cancer

PURPOSE

The aim of the study was to compare the dose distributions of combined intracavitary and interstitial (IC/IS) brachytherapy with 3-catheter IC brachytherapy in treating locally advanced (stage IIB) cervical cancer.

METHODS AND MATERIALS

In total, 46 patients were included, each with stage IIB cervical cancer, local lesion sizes ≥5 cm, and tumors that had not regressed after 45 Gy/25 F external intensity-modulated radiotherapy. To identify the dosimetric advantage of delivering a local boost to high-risk (HR)-cervix in IC/IS, patients were divided into two groups: IC/IS and IC/IS + HR-cervix. The differences in dosimetric parameters were compared between the two groups. Comparisons were then made between the parameters of the four planning methods: IC (Point A), IC (three dimensional [3D]), IC/IS, and IC/IS + HR-cervix.

RESULTS

In patients with IC/IS implants, the relative uterine tandem dwell time was significantly extended in the IC/IS + HR-cervix group, and the V150 and V200 volumes of HR-cervix were increased (all p < 0.001), whereas the D90 and D100 values of the IC/IS + HR-cervix group were lower than those in the IC/IS group. In pairwise comparisons, HR-cervix V150 and V200 values were lowest in the IC/IS group, followed by the IC (3D), IC/IS + HR-cervix, and IC (Point A) groups. All differences were statistically significant (p < 0.05), with the exception of IC/IS vs. IC (3D).

CONCLUSIONS

When treating locally advanced cervical cancer (stage IIB, local residual volume ≥5 cm after external radiotherapy), the IC/IS + HR-cervix optimization method can meet the HR clinical target volume D90 dose requirement, normal tissue dose limits, and can escalate doses to local areas of the cervix.

Analysis of dose-effect relationship between DVH parameters and clinical prognosis of definitive radio(chemo)therapy combined with intracavitary/interstitial brachytherapy in patients with locally advanced cervical cancer: A single-center retrospective study

PURPOSE

The purpose of the study was to explore the dose-effect relationship between dose-volume histogram parameters and clinical prognosis of definitive radio(chemo)therapy followed by intracavitary/interstitial brachytherapy in locally advanced cervical cancer.

METHODS AND MATERIALS

A retrospective analysis was performed on 110 patients with locally advanced cervical cancer who underwent external beam radiotherapy combined with intracavitary/interstitial brachytherapy with or without chemotherapy from July 2010 to September 2018. We reported D₁₀₀, D₉₈, and D₉₀ for high-risk clinical target volume (HR-CTV) and intermediate-risk clinical target volume, D_2cm³ for organs at risk. Multivariate Cox regression was used to screen independent factors. Dose-volume parameters screened by the Cox regression were incorporated into the probit model for investigating its relationship with survival.

RESULTS

The median followup time was 72.33 months. Multivariate Cox regression analysis showed that HR-CTV D₁₀₀, HR-CTV D₉₈, and HR-CTV D₉₀ were independent factors, affecting the 5-year overall survival (OS), cancer-specific survival (CSS), and local control (LC) rates. The probit model showed that HR-CTV D₉₈ had predictive values for the 5-year OS, CSS, and LC, and HR-CTV D₁₀₀ had predictive values for the 5-year OS, CSS, whereas HR-CTV D₉₀ had a predictive value only for the 5-year OS. The HR-CTV D₉₈ corresponding to OS _ED90, CSS _ED90, and LC _ED90 was 86.8, 85.6, and 78.6 Gy, respectively.

CONCLUSIONS

A significant dependence of OS, CSS, and LC on D₉₈ for HR-CTV was found. When the long-term OS, CSS, and LC rate of the patient was >90%, HR-CTV D₉₈ > 86.8 Gy _EQD2, 85.6 Gy _EQD2, and 78.6 Gy _EQD2 were required.

Interstitial High-Dose-Rate Gynecologic Brachytherapy: Clinical Workflow Experience From Three Academic Institutions

An interstitial brachytherapy approach for gynecologic cancers is typically considered for patients with lesions exceeding 5 mm within tissue or that are not easily accessible for intracavitary applications. Recommendations for treating gynecologic malignancies with this approach are available through the American Brachytherapy Society, but vary based on available resources, staffing, and logistics. The intent of this manuscript is to share the collective experience of 3 academic centers that routinely perform interstitial gynecologic brachytherapy. Discussion points include indications for interstitial implants, procedural preparations, applicator selection, anesthetic options, imaging, treatment planning objectives, clinical workflows, timelines, safety, and potential challenges. Interstitial brachytherapy is a complex, high-skill procedure requiring routine practice to optimize patient safety and treatment efficacy. Clinics planning to implement this approach into their brachytherapy practice may benefit from considering the discussion points shared in this manuscript.