Interstitial needles versus intracavitary applicators only for locally advanced cervical cancer: results from real-life dosimetric comparisons.

Background and purpose: Image-guided adapted brachytherapy (IGABT) is superior to other radiotherapy techniques in the treatment of locally advanced cervical cancer (LACC). We aimed to investigate the benefit of interstitial needles (IN) for a combined intracavitary/interstitial (IC/IS) approach using IGABT over the intracavitary approach (IC) alone in patients with LACC after concomitant external beam radiotherapy (EBRT) and chemotherapy. Materials and methods: We included consecutive patients with LACC who were treated with IC/IS IGABT after radiochemotherapy (RCT) in our retrospective, observational study. Dosimetric gain and sparing of organs at risk (OAR) were investigated by comparing the IC/IS IGABT plan with a simulated plan without needle use (IC IGABT plan) and the impact of other clinical factors on the benefit of IC/IS IGABT. Results: Ninety-nine patients were analyzed, with a mean EBRT dose of 45.5 ± 1.7 Gy; 97 patients received concurrent chemotherapy. A significant increase in median D90% High Risk Clinical target volume (HR-CTV) was found for IC/IS (82.8 Gy) vs IC (76.2 Gy) (p < 10-4). A significant decrease of the delivered dose for all OAR was found for IC/IS vs IC for median D2cc to the bladder (77.2 Gy), rectum (68 Gy), sigmoid (53.2 Gy), and small bowel (47 Gy) (all p < 10-4). Conclusion: HR-CTV coverage was higher with IC/IS IGABT than with IC IGABT, with lower doses to the OAR in patients managed for LACC after RCT. Interstitial brachytherapy in the management of LACC after radiotherapy provides better coverage of the target volumes, this could contribute to better local control and improved survival of patients.

Automatic reconstruction of interstitial needles using CT images in post-operative cervical cancer brachytherapy based on deep learning.

Purpose: The purpose of this study was to investigate the precision of deep learning (DL)-based auto-reconstruction in localizing interstitial needles in post-operative cervical cancer brachytherapy (BT) using three-dimensional (3D) computed tomography (CT) images. Material and methods: A convolutional neural network (CNN) was developed and presented for automatic reconstruction of interstitial needles. Data of 70 post-operative cervical cancer patients who received CT-based BT were used to train and test this DL model. All patients were treated with three metallic needles. Dice similarity coefficient (DSC), 95% Hausdorff distance (95% HD), and Jaccard coefficient (JC) were applied to evaluate the geometric accuracy of auto-reconstruction for each needle. Dose-volume indexes (DVI) between manual and automatic methods were used to analyze the dosimetric difference. Correlation between geometric metrics and dosimetric difference was evaluated using Spearman correlation analysis. Results: The mean DSC values of DL-based model were 0.88, 0.89, and 0.90 for three metallic needles. Wilcoxon signed-rank test indicated no significant dosimetric differences in all BT planning structures between manual and automatic reconstruction methods (p > 0.05). Spearman correlation analysis demonstrated weak link between geometric metrics and dosimetry differences. Conclusions: DL-based reconstruction method can be used to precisely localize the interstitial needles in 3D-CT images. The proposed automatic approach could improve the consistency of treatment planning for post-operative cervical cancer brachytherapy.

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.

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.

First pointwise encoding time reduction with radial acquisition (PETRA) implementation for catheter detection in interstitial high-dose-rate (HDR) brachytherapy.

PURPOSE: A pointwise encoding time reduction with radial acquisition (PETRA) sequence was optimized to detect empty catheters in interstitial (HDR) brachytherapy with clinically acceptable spatial accuracy for the first time. Image quality and catheter detectability were assessed in phantoms, and the feasibility of PETRA's clinical implementation was assessed on a gynecological cancer patient. METHODS AND RESULTS: Empty catheters embedded in a gelatin phantom displayed positive signal on PETRA and more accurate cross-sections than on clinically employed T2-weighted sequences, differing by 0.4 mm on average from their nominal 2 mm diameter. PETRA presented minimal susceptibility differences and a symmetric metal artifact, contrary to the clinical sequences. The PETRA-CT catheter tip position differences assessed by a treatment planning system (TPS) were < 1 mm. PETRA also detected an interstitial template with empty catheters penetrating a poultry phantom and fused very well with CT. Interstitial catheter positional difference between PETRA and CT images was < 1 mm on average, increasing with distance from isocenter. All interstitial catheters and the employed interstitial template were detected on PETRA images of an endometrial adenocarcinoma patient. Empty needles were traceable using a TPS, with higher spatial resolution and more favorable contrast than on T2-weighted images used for contouring. A treatment plan could be produced by combining information from PETRA for catheter detection and from T2-weighted images for tumor and organs delineation. CONCLUSIONS: PETRA detected successfully and accurately interstitial catheters in phantoms. Its first clinical implementation shows a potential for MR-only treatment planning in interstitial HDR brachytherapy.

[Dose optimization in 3D pulsed dose rate brachytherapy for patients with locally advanced cervical cancer: A French multicenter phase II trial]. / Optimisation de la curiethérapie utérovaginale de débit pulsé des cancers du col utérin localement évolués : résultats finaux du PHRC Tridicol.

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.

Dosimetric considerations when utilizing Venezia, Capri, Rotte double tandem, and tandem and ring with interstitial needles for the treatment of gynecological cancers with high dose rate brachytherapy.

This work evaluated the difference in dosimetry of high dose rate (HDR) brachytherapy treatments between plans using advanced multichannel applicators and simplified base versions. Eighteen HDR patients treated using Interstitial Ring CT/MR Applicator Set (Elekta Brachytherapy, Netherlands) (TRN) (21 plans), CapriTM Applicator Set (Varian Medical Systems, Inc., Palo Alto, CA) (CC) (19 plans), Rotte Endometrial Applicator Set (Elekta Brachytherapy, Netherlands) (RDT) (18 plans), and the Advanced Gynecological Applicator Venezia (Vz) (Elekta Brachytherapy, Netherlands) (6 plans) were retrospectively reviewed. For each plan, "advanced" channels including any interstitial channels, the 12 noncentral channels in the CC, and the lateral extending aspects of the RDT were removed and a new plan with the original inverse planning settings was optimized using only the remaining "simplified" applicator and compared to the original. The new plans were renormalized to match the original percent dose to 90% of the high-risk clinical target volume (HR-CTV). Critical structures included bladder, rectum, sigmoid colon, and small bowel. Comparisons were made utilizing dose volume histograms of HR-CTVs, conformation number (CN), and the equivalent total dose in 2 Gy fractions (EQD2) to 2 cm3 of the normal structures. Comparing simplified to advanced plans, the average percent differences in EQD2 to 2 cm3 for Vz, with 95% confidence interval, were 101.7 ± 85.9%, 147.8 ± 76.7%, 95.3 ± 61.6%, and 44.0 ± 12.4% for Rectum, Bladder, Sigmoid, and Bowel, respectively. For TRN: 36.9 ± 18.5%, 38.2 ± 14.5%, 20.3 ± 8.8%, and 15.3 ± 8.2%. For CC: 18.9 ± 3.7%, 12.3 ± 5.3%, 27.8 ± 7.1%, and 17.1 ± 3.6%. For RDT: 1.5 ± 6.8%, 7.4 ± 6.7%, 11.1 ± 4.4%, and 8.0 ± 8.7%. The CN was better in advanced applications by 0.024 for RDT, 0.104 for TRN, 0.043 for CC, and 0.251 for Vz (all p < 0.05). Advanced multichannel treatments allow better target dose conformation and normal tissue dose manipulation. The biggest factors influencing the brachytherapy dose distributions are the number of available channels and their separation from each other within the target.

Impact of brachytherapy technique (2D versus 3D) on outcome following radiotherapy of cervical cancer.

Purpose: The purpose of this study was to analyze the effect of 2D conventional brachytherapy (CBT) compared to 3D MRI-guided brachytherapy (IGBT) with and without the use of interstitial needles on local control, overall survival, and toxicity in patients treated for cervical cancer with radiation or chemoradiation. Material and methods: A retrospective analysis was performed of biopsy-proven FIGO IB-IVA cervical cancer patients, treated with primary radiation or chemoradiation, followed by brachytherapy (BT) between January 1997 and July 2016. Endpoints were local control, overall survival, and toxicity. Results: Of 126 patients included, 35 have been treated with CBT, 31 with IGBT without needles (IC), and 60 with IGBT with needles (ICIS). External beam radiotherapy (EBRT) had mostly been delivered concurrently with chemotherapy (weekly cisplatin). Overall local control was 93% after 1 year, and 88% after 3 years. Overall 3-year survival was 75%, and 5-year survival was 66%. The 3D technique (IGBT cohorts) showed a trend for an improved local control and overall survival (p = 0.05) compared to the 2D technique (CBT cohort). A decrease in toxicity was observed from 17% (2D cohort) to 12% (3D cohort). The use of interstitial needles was associated with a higher high-risk clinical target volume (HR-CTV) dose (11.3 Gy vs. 9.9 Gy) and a lower D2cc bladder dose (10.9 Gy vs. 14.7 Gy, both p < 0.01). Conclusions: In cervical cancer treatment, the use of a 3D brachytherapy technique (MRI-guided with or without interstitial needles) showed a trend towards an increased local control and improved overall survival with reduced toxicity, compared to the conventional 2D brachytherapy technique. The use of interstitial needles allowed dose sculpting, resulting in delivery of higher doses to the HR-CTV, while reducing radiation doses to organs at risk, such as the bladder.