HDR Intracavitary Brachytherapy Research Articles

Feasibility of Using a Single Planning MRI for Two-Insertion Intracavitary Brachytherapy for Cervical Cancer

MRI is an essential tool in treatment planning for cervical cancer patients undergoing definitive chemoradiation involving brachytherapy. However, due access to MRI for many patients may be limited. We sought to examine the feasibility and quality of treatment planning for organs at risk (OAR) and target volumes of a single treatment planning MRI for a planned two-insertion HDR intracavitary cervical brachytherapy. Eighteen patients with cervical cancer who underwent MRI-based treatment planning for intracavitary brachytherapy were selected for analysis. Patients underwent two intracavitary applicator insertions using a tandem and ring applicator (TnR_1 and TnR_2) with both CT (for digitization only) and MRI following each insertion and two fractions delivered with each insertion (total 7 Gy x 4fx). MRI-based TnR_2 plans were retrospectively replanned with the following procedure: 1) register MRI from TnR_1 to TnR_2 CT, 2) transfer cervix contour (Cx_simul) and plan from TnR_1 to TnR_2 CT, simulating blinding from TnR_2 MRI, 3) crop Cx_simul from TnR_2 OARs, 4) adjust plan only to meet OAR constraints or clinical doses if clinical plan (TnR_2 original MRI plan summed with TnR_1 and EBRT doses) violates constraints. Coverage changes (∆_D90%) in actual MRI defined TnR_2 cervix (Cx_real) was compared to clinical plans and evaluated against our clinical target goal: >85 Gy EQD2 (EBRT+BT). Differences between Cx_simul and Cx_real contours were evaluated with Dice Similarity Coefficient (DSC). Changes in bladder, rectum, rectosigmoid, and bowel D2cc was evaluated. Procedure time was recorded to determine time added by MRI (time between CT and final MRI timestamps; n = 29). Plan modification to meet OAR constraints was required for 5/18 plans. Cx_real target coverage from clinical to simulated plans decreased in 7/18 plans (∆_D90% = 1.7±6%). Composite EQD2 was <85 Gy in 2/18 cases, with ∆_D90% of -1.3% (clinical EQD2<85 Gy for this case also) and -7.3%, which was due to inconsistent cervix shape between insertions 1 and 2. Cervix DSC values between Cx_simul and Cx_real ranged from 0.68-0.88 (mean = 0.78 ± 0.06). Bladder, rectum, rectosigmoid, and bowel D2cc increased on average 4 ± 12%, 3 ± 9%, 5 ± 10%, and 5 ± 17%, respectively. Including planning MRI increased procedure time by 41.8 ± 10.4 min. The proposed method of utilizing TnR_1 MRI contours for TnR_2 CT planning reduces procedure time and provides reasonable target coverage for most cases. OAR assessment varies between imaging modality which likely represents variability in OAR position rather than treatment planning modality. Next steps are to increase patients studied, and implement this technique prospectively while waiting for TnR_2 MRI completion and compare the clinical TnR_2 MRI plan with the TnR_2 CT plan created with Cx_simul. This will provide further confidence in validity of the approach and ensure plan quality is maintained prior to full implementation.

A Novel Method for Intracavitary Cervical HDR Brachytherapy: Express Finger-Guided Implant Insertion at Simulation Table without Speculum, Cervical Dilatation, Sleeve, Anesthesia, or Sedation

Our purpose is to develop a fast, effective, and independent intracavitary brachytherapy implant insertion method that does not need sleeve insertion, anesthesia or conscious sedation, and that can be performed at the front edge of the simulation table (CT or MRI), using finger guidance without a need for speculum or cervical dilatation. From February 2022 to January 2023, we treated 27 locally advanced cervical cancer patients. In the last week of EBRT, we assessed patients with MRI and pelvic exam to determine their eligibility: 89% (24 patients) met the two inclusion criteria for the express insertion which are: the ability to cover any residual disease with intracavitary brachytherapy, and the accessibility of cervix external os. Each patient had 3 HDR express insertions (8Gy x3). A total of 72 consecutive express implant insertions were performed. Each insertion is evaluated for the success of procedure, number of attempts, and time taken. Patients started on laxative 3 days prior to the procedure, and paracetamol & Ibuprofen taken at home 2 hours before the procedure. On arrival, patients used the bathroom, and IM/SC morphine given. Patients were prepared at the front edge of the simulation table and topical lidocaine applied to the cervix. The external os identified with the index finger of one hand which also guided the tandem insertion using the other hand. No cervical dilatation was used. CT simulation was performed to confirm adequate implant placement and to contour and plan CTV-HR and OARs as per GEC-ESTRO/ABS guidelines. The success rate was 100% in all the 72 express insertions. >90% (66 insertions) were smooth and fast, i.e., completed in 1 attempt that took <20 minutes. <10% (6 insertions) were challenging but successful, in 2 patients: one patient had an acute anteverted uterus for which suprapubic abdominal pressure facilitated the procedure that took <3 attempts and completed in <40 minutes, the other patient had an acute retroverted uterus which was associated with the most challenging procedure that took >3 attempts and completed in >40 minutes. The success rate was not affected by the type of applicator used. 85% of our applications used multichannel tandem and cylinder, 10% used tandem and ovoids, and 5% used tandem and ring applicators. Express finger-guided intracavitary brachytherapy implant insertion at the simulation table without speculum, cervical dilatation, sleeve, anesthesia, or sedation is fast, effective, and an independent method that can be used in most cervical cancer patients to complete their planned brachytherapy treatment regardless of limited resources. Practice and dissemination of this innovative method is important especially when operative rooms and anesthesia support are limited (e.g., epidemics and closures) and in centers lacking such support. Further studies are warranted to optimize the procedure and to highlight its significant medical and socioeconomic benefits.

Comparative Analysis of Dosimetry and Treatment Outcomes of Two Different Dose Fractionation Schedules of HDR Brachytherapy in Carcinoma Cervix Amid Covid-19 Pandemic

Background: Cervical carcinoma is the fourth most common cancer and leading cause of cancer related deaths in women worldwide. Brachytherapy is an important part in the treatment of cervical cancer. Delivering HDR Intracavitary Brachytherapy in the Covid-19 era is challenging. Objective: To compare the dosimetry and treatment outcomes between two fractionation schedules of 9Gy in 2 fractions v/s 7Gy in 3 fractions of high dose rate Brachytherapy in patients with locally advanced carcinoma cervix. Methods: A randomized observational study was carried out on 80 histopathologically proven squamous cell carcinoma patients of cervix. All patients were treated with EBRT 50Gy in 25 fractions over a period of 5 weeks (2Gy/#) with concurrent weekly cisplatin 30mg/m2. After assessing fitness for brachytherapy, patients in the study arm received HDR intracavitary brachytherapy in 9Gy for 2 fractions v/s 7Gy for 3 fractions in the control arm. Results: The median time of follow-up was 14 months for the study (range 7 – 20 months). Local control rate was 89.75% for study arm and 92.30% for control arm. One year disease free survival in the study arm was 76.92% as compared to 74.35% in the control arm. Median disease-free survival was better in the study arm (14 months v/s 12 months) with a trend of significant benefit. Rectal and bladder toxicities were comparable in both the arms. Median dose to ICRU bladder and rectal point, and EQD2 dose in both arms were not found to be statistically significant. Conclusion: Both the regimes were found to be safe. Disease response and toxicities were also similar in both the arms. There was a better patient compliance with 9Gy for 2 fractions schedule in view of lesser number of fractions resulting in less hospital visit in the Covid-19 pandemic.

Comparison of two high dose rate intracavitary brachytherapy regimens in treatment of cervical cancer: a preliminary report

BackgroundTo assess and compare the local control and toxicities between HDR Intracavitary Brachytherapy with 7.5 Gy and 9 Gy per fraction after EBRT in treatment of carcinoma cervix.MethodologyA total of 180 patients were randomly assigned to 2 arms. Arm A received HDR intracavitary brachytherapy with a dose of 7.5 Gy per fraction, 1 fraction per week for 3 fractions and Arm B received 9 Gy per fraction, 1 fraction per week for 2 fractions. Patients were evaluated on follow up for assessment of local control and toxicities.ResultsThe median follow up was 12 months (6–18 months). In arm A 89% of the patient had complete response and 11% had recurrence or metastasis. In arm B 93% of the patient had complete response and 7% had recurrence or metastasis. Grade 2/3 diarrhoea was seen in 4.4% of patients in Arm A and in 7.7% in Arm B. Grade 2/3 proctitis was seen in 3.3% of patients in 7.5 Gy arm and in 6.6% in 9 Gy arm. One patient in each arm had grade 1 haematuria. The overall duration of treatment was significant lower in Arm B compared to Arm A (59 days vs 68 days, p = 0.01).ConclusionThe result of this clinical study shows that Intracavitary brachytherapy with a dose of 9 Gy per fraction is non inferior to other schedules in term of local control and does not result in increased toxicity.

PO44 Presentation Time: 4:45 PM: HDR Intracavitary Brachytherapy in the Management of Recurrent VaIN3: A Case Report and Review of the Literature

<h3>Purpose</h3> Vaginal intraepithelial neoplasia, or VaIN, is a pre-cancerous condition in the cell of the vagina. It has an estimated occurrence of 0.2-0.3 cases per 100,000 women in the U.S. It is classified into three groups based on histologic characteristics: low-grade (VaIN 1), intermediate-grade (VaIN 2), and high-grade (Vain 3). High-grade lesions includes vaginal carcinoma-in-situ and are known as a pre-malignant lesion most likely to progress to vaginal cancer. Risk factors include HPV, cigarette smoking and immunodeficiency. VaIN 1 are usually treated with close observation; VaIN 2 and 3 usually require prompt treatments including excision (wide local excision, partial or total vaginectomy), ablation (CO2 laser, ultrasonic surgical aspiration), topical therapy (imiquimod, fluorouracil), and radiation therapy. Yet no standard treatment exists. Given that it is a rare pre-malignant condition, there have been limited reports on the use of intracavitary brachytherapy. Proper dose prescription remains challenging, especially for patients with history of hysterectomy. <h3>Materials and methods</h3> We report a case of a 70 year-old female with history of hysterectomy 15 years ago for endometriosis and recurrent diffuse VaIN3 that was refractory to multiple lines of local therapy who received HDR cylinder brachytherapy. The report includes clinical and diagnostic studies, dosimetric considerations in treatment planning for improved target coverage, and a review of the limited existing literature of HDR brachytherapy for VaIN3. <h3>Results</h3> HDR, MDR and LDR had all been utilized to treat VaIN with comparable tumor control and toxicity. Reported acute side effects include vaginitis, urethritis, and proctitis; whereas late side effects include vaginal atrophy/fibrosis/telangiectasia/stenosis. What made this case especially challenging is her past surgical history of hysterectomy. The vaginal vault is difficult to assess after hysterectomy with potential abnormal cells sequestered above the suture line, and is thus prone to underdosing. Therefore some institutions prefer to use ovoids rather than cylinder to adequately cover the upper vagina; whereas others argue that cylinder is better for treating extensive lesions by providing a uniform coverage of the entire vagina despite higher toxicity. Upper vagina is also noted to tolerate a higher radiation dose compared to lower vagina. Doses are often prescribed to different depths based on location in the vagina, or on doses to the OARs. Our patient was treated with a dose of 30Gy in 5 fractions given twice weekly, prescribed to 3mm depth for the proximal 3cm vagina and to surface for the remaining 5cm vagina. She had complete clinical response and was encouraged to continue vaginal dilator use to prevent vaginal stenosis and regular follow-ups with pelvic exams. <h3>Conclusions</h3> HDR brachytherapy is a feasible and effective alternative approach to treat patients who are non-surgical candidates, have recurrent disease or disease refractory to previous treatments, or have extensive multifocal VaIN. Our case would be a valuable addition to the existing limited literature regarding the treatment efficacy and proper dose prescription for this rare condition.

MSS05 Presentation Time: 4:05 PM: HDR Brachytherapy for Pediatric Vaginal Rhabdomyosarcoma: Two Case Reports with Long-Term Follow Up

<h3>Purpose</h3> Rhabdomyosarcomas (RMS) are the most common soft tissue tumor in children with over 400 cases diagnosed each year. Vaginal RMS is exceedingly rare, accounting for 4% of all RMS and 10% of female RMS. Outcomes are favorable with 10-year overall survival rates estimated to be over 90%. Current standard of care requires multidisciplinary approach involving chemotherapy and local therapy. To limit late effects from treatment, local therapy has advanced from radical surgeries to no local treatment in those with complete response or favoring radiation therapy for those with residual disease following chemotherapy. There is limited data on modern brachytherapy techniques for the management of vaginal RMS. Here we report two cases of pediatric vaginal RMS treated with HDR intracavitary brachytherapy at our institution and long-term follow up. <h3>Methods and Materials</h3> Following IRB approval, we identified two pediatric patients who were treated at our institution with HDR brachytherapy for RMS between 2017 and 2019 and had follow up data available. We collected demographics, presenting information, treatment data including chemotherapy, surgery if applicable, brachytherapy plans, and outcomes. <h3>Results</h3> Both patients presented at outside hospitals at the age of 2 with a prolapsing vaginal mass. Biopsies were consistent with botryoid vaginal RMS. They were referred to our institution for consideration of radiation therapy after completion of 12 weeks of VAC-based chemotherapy. Post-chemotherapy MRIs were obtained to assess extent of residual disease and a vaginal applicator was placed at the time of MRI for HDR brachytherapy planning. Both patients had good response with small areas of residual thickening along the vaginal wall. The first patient underwent exam under anesthesia, vaginal dilation and removal of visualized gross disease prior to brachytherapy. A 2.2 cm Syed obturator was used with a straight central tandem positioned at the proximal end of the obturator for central loading with 2 additional flexible catheters placed in the posterior grooves of the Syed obturator. The 3 channels allowed for coverage of the posterior and proximal vaginal disease seen on her post-chemotherapy MRI. On her last fraction, she was noted to have vaginal swelling and difficulty with inserting the Syed obturator, therefore, a 2 cm Varian single channel cylinder was used for her last fraction. For the second patient, a custom designed vaginal cylinder was made by machining a hole through a 1.3 cm vaginal dilator with a catheter inserted and affixed in the central canal. Both patients were prescribed 4.9 Gy x 6 fractions treated three times weekly with the goal of obtaining an equivalent total dose of 36 Gy with 45 Gy to the vaginal surface. The first patient was prescribed to 5mm depth and the second patient to 3mm depth based on extent of residual disease. Both patients tolerated treatment well with minimal bleeding on cylinder insertion and expected acute side effects including cystitis, dysuria and acute vaginal discomfort that resolved with sitz baths and barrier ointments. With 4 and 3 years follow up, respectively, both patients have no evidence of disease on MRI imaging and no evidence of long-term toxicities related to their brachytherapy. <h3>Conclusions</h3> Vaginal RMS is a rare cancer and thus there is limited modern experience with HDR brachytherapy as a means for local control in this patient population. Here were present two cases where devices relatively common in gynecologic brachytherapy practices can be used and customized to cover small tumors in pediatric patients. Our experience has shown that for select patients, HDR brachytherapy can be a safe, tolerable, and efficacious treatment modality for vaginal RMS.

PHSPP05 Presentation Time: 3:10 PM: Optimization Strategies in MR-Only Workflow for Interstitial and Intracavitary Gynecological HDR Brachytherapy

<h3>Purpose</h3> Image-guided interstitial and intracavitary gynecological brachytherapy (IGBT) is advancing towards MR-only workflows because of MR's superior soft-tissue contrast for tumor delineation and tissue segmentation. However, current treatment planning still necessitates the use of CT/MR fusion to aid in needle reconstruction and quality assurance (QA). In this work, we present strategies to visualize needles on MR and provide QA procedures for MR-only IGBT with comparisons to the conventional CT/MR approach. <h3>Materials and Methods</h3> Three 6F interstitial plastic needles and one CT/MR-compatible intrauterine tandem and ring (T&R) applicator set were examined in this study with the Flexitron afterloading system (Elekta Brachytherapy, Netherlands). To visualize the needles, they were immersed in demineralized water and scanned without markers in a 3T MRI system (Signa Premier; GE Healthcare, Milwaukee, WI). MR images were acquired with three protocols: 3D T1W (TR\TE 552\10 ms, and 1 mm voxel), 3D T2W (TR\TE 3051\104 ms, and 1 mm voxel) and silent Zero TE sequence (TR\TE 1060\20 ms, and 0.58 mm voxel). For QA, a 2D MR protocol (T1W, 7-10 mm thick slice) was utilized that allowed a projection-like image of an EBT3-film-based setup which was also imaged (with CT/x-ray markers) in CT (Philips, Netherlands) and x-ray imager (Varian Medical Systems, Palo Alto, CA). This setup consists of attaching catheters and four vitamin-D pills to EBT3 film pieces. The four corners of each film piece (5" x 4") were marked with skin markers that are visible in CT and MR images. These skin markers served as surrogates for a 4-point registration system between all images, and the vitamin-D pills were used to assess registration quality. An efficient film handling/scanning protocol was designed for this work and the source first dwell position (FDP) on the film was determined using a commissioned source localization algorithm. The FDP was compared between film, x-ray/CT markers, and applicator library models. <h3>Results</h3> For needle visualization, ZTE images generated a positive contrast for the interstitial needles as compared to conventional T1 and T2 images (See Figure). For QA, the 2D MR slice and x-ray image clearly displayed applicators, needles, vitamin-D pills, and skin markers allowing accurate registration to film images, visualization, and localization of the catheters, source positions, and markers in one fused image (See Figure). The tandem tip from MR was 1.1 mm longer than that of the x-ray and model which was not evident in the vitamin-D matching, implying a potential MR artifact at the tip (Sub-Figure B) which should be taken into account while planning. FDP reconstruction errors from the needle tip in MR with respect to film and x-ray markers were less than 1 mm (Sub-Figure D). <h3>Conclusions</h3> While further investigation is required, ZTE imaging offers a promising alternative to CT imaging for needle reconstruction supporting MR-only gynecological brachytherapy treatment planning. However, MR-only workflow requires special considerations in QA to account for possible systematic shifts that could exceed the level of accuracy achieved in x-ray-based IGBT.

Friday, June 17, 20223:30 PM - 3:45 PMPO12: Time Investment and Planning Benefit of Serial Treatment Planning MRI Scans for HDR Intracavitary Brachytherapy for Cervix Cancer

<h3>Purpose</h3> To estimate the time investment and planning benefit of acquiring treatment planning MRI scans for each insertion for tandem and ring (T&R) cases. <h3>Materials and Methods</h3> Fourteen (14) consecutive cervical cancer patients who underwent intracavitary HDR brachytherapy with T&R applicator were retrospectively analyzed. All patients received 28Gy in 4 fractions delivered in 2 insertions (Ins1 and Ins2), with 2 fractions per insertion, after completion of EBRT. All insertions were performed under general anesthesia with intraoperative CT and MRI guidance. Target (Cx) and normal tissues were contoured on each MRI scan at the time of the procedure. Four patients who did not have both insertions using MRI planning were excluded. Image registration of Ins2 to Ins1 was retrospectively performed in Eclipse (Varian Medical Systems, Palo Alto, CA) based on applicator position. Target contour from Ins2 (Cx2) was copied to the Ins1 structure set (Cx2reg) using this registration. The following metrics were recorded: volume of Cx1, Cx2, and dice similarity coefficient of the two [DSC = 2*(volCx1+volCx2)/(overlap between Cx1 and Cx2reg)] (0 indicates no overlap between the contours; 1 indicates perfect overlap). Target D90 using MRI for each insertion (D90 Cx1 on plan of Ins1 + D90 Cx2 on plan of Ins2) and using only Ins1 MRI (D90 Cx1 on plan of Ins1 + D90 Cx2reg on plan of Ins1). One patient had a replan for the second fraction of the first insertion was therefore excluded from the D90 analysis. Additional time required for MRI-based planning was calculated using the timestamps of the last in-room CT and of the T2 MRI. <h3>Results</h3> Cx1 and Cx2 volumes [median, interquartile range (IQR)] were 26.0 cm³ (IQR 11.3 cm³) and 22.9 cm³(IQR 16.7 cm³). DSC was 0.73 (IQR 0.05). Target D90 (as % of prescription dose) using MRI for each insertion vs. using only Ins1 MRI information for Ins2 was 109.6% (IQR 4.8%) vs. 110.1% (IQR 7.5%). Additional time for MRI-based planning was 38.8 minutes (IQR 6.3 minutes). <h3>Conclusions</h3> The addition of an MRI for Ins2 added only modest alterations in the target volume and D90, however, did add approximately 40 minutes of added time under anesthesia. The projected target coverage if Cx1 was used in insertion 2 instead of Cx2 would be sufficient and could be more efficient in terms of scan and, potentially, contouring time. This study supports the hypothesis that the time commitment required for MRI acquisition for Ins2 may not be justified by a planning advantage. Limiting factors of this study: contouring and fusion uncertainties; our methods did not consider changes in organs-at-risk between insertions; limited number of patients.

Simultaneous or Sequential Boost to Clinically Involved Lymph Nodes in Cervical Cancer

<h3>Purpose/Objective(s)</h3> The optimal approach to metastatic lymph nodes (LNs) in locally advanced cervical cancer (LACC) is controversial. This study aimed to evaluate the efficacy and toxicity profile of dose escalation with simultaneous integrated (SIB) or sequential boost (SB) for clinically positive LNs in LACC. <h3>Materials/Methods</h3> The data of 43 patients who underwent chemoradiotherapy (CRT) with a SIB or SB dose to positive LNs between 2015 and 2021 for LACC were retrospectively analyzed. All patients were applied 50.4 Gy intensity-modulated radiotherapy (IMRT) or modulated volumetric arc therapy (VMAT) to the lymphatic and primary regions in 28 fractions with concurrent platinum-based chemotherapy followed by 28 Gy HDR intracavitary brachytherapy (BRT) in four fractions. Response evaluations were performed via magnetic resonance imaging (MRI) and positron emission tomography (PET)-CT on the third month. <h3>Results</h3> Median age was 53 years (range: 34-80 years). The FIGO stage was IIIC1 in 30 (70%), IIIC2 in 10 (23%), and IVA in three patients (7%), respectively. Pelvic CRT was applied to 25 patients (58%), and pelvic-paraaortic CRT was applied to 18 patients (41%). A total of 94 LNs were boosted. The median longest diameter of the LNs was 1.7 cm (range: 1–7 cm) and median volume was 2.5 cc (range: 0.6-21.5 cc). A SIB was applied in 24 (56%), SB in 13 (30%), and both in 6 patients (14%), respectively. Patients in the SIB group received a total dose of 56-64 Gy in 28 fractions. The patients with SB on the other hand received 56.4-60.4 Gy in 31-33 fractions and patients with SIB+SB received 60-66 Gy in 30-32 fractions. The dose from the BRT was also calculated to the LNs and the minimum dose to LNs from BRT was between 0-7.6 Gy (median 3.6 Gy). The maximum dose from BRT was as 0-9.7 Gy (median 4.8 Gy). Median follow-up (FU) was 21 months (range: 3-77 months). Following CRT, 41 (98%) patients had a complete response (CR) and one (2%) had a partial response (PR) in boosted LNs on MRI whereas 39 (98%) patients had a CR and one (2%) had a PR on PET/CT. Recurrence occurred in 12 patients during FU: one local recurrence (LR), two regional recurrence out of the RT field, seven distant metastases (DM), and two LR+DM. There was no recurrence in any of the 94 boosted LNs and the local control (LC) rate was 100%. The 1- and 2-year rate of overall survival was 89.5% and 82.3%, disease-free survival was 80% and 65.8%, locoregional recurrence-free survival was 84.6% and 70.5%, and DM-free survival rate was 80.4% and 69.9%, respectively. Treatment was well tolerated without any serious acute toxicity. Grade 3 late toxicity was observed in two patients (1-rectovaginal fistula, 1-ureteral stenosis). <h3>Conclusion</h3> Dose escalation with IMRT/VMAT yields an excellent LC rate for the involved LNs, even for very large ones, in LACC with a low toxicity profile. Routine LN dissection may not be necessary for patients with a LACC, but prospective randomized trials are needed to clarify this.

Comparison of dose volume histograms and international commission of radiation units and measurement point doses to bladder and rectum in carcinoma cervix patients treated with intracavitary brachytherapy in department of radiotherapy

International commission of radiation units and measurement point doses to the bladder and rectum in carcinoma cervix patients treated with intracavitary brachytherapy in the department of radiotherapy. The aim: to evaluate two-dimensional point-based dose planning and three-dimensional computed tomography-based dose-volume parameters for high-dose-rate intracavitary brachytherapy of cervical cancer. Materials and methods: prospective study done between the years June 2018 to April 2020, a total of 50 prospectively registered women of non-metastatic carcinoma cervix treated with definitive concurrent chemo-radiotherapy followed by HDR intracavitary brachytherapy who met inclusion criteria were accrued in the study. All women in the study were treated with 50 Gy EBRT then assessment was done for response and adequacy for comfortable insertion of application. Brachytherapy procedure was performed under sedation in the lithotomy position. Results: Median age of the entire group was 54.5 years, majority of them were in their 5th (34 %) or 4th (28 %) decade. Pathologically, all were squamous cell carcinoma. Most common subtype was large cell non keratinizing type (64 %). Major bulk of the study is contributed by stage IIA, IIB, IIIB. All patients were treated with external beam radiotherapy of 50Gy in 25 fractions with 2Gy per fraction followed by high dose rate brachytherapy of 7 Gy per fraction for 3 fractions, one week apart to a total intracavitary brachytherapy dose of 21Gy. Conclusion: Results from the study suggests that rectum ICRU reference points can be surrogate markers for D2cc, but not for bladder and hence reporting should preferably be done in volumetric method rather than reference point doses

CONCURRENT CHEMORADIATION WITH WEEKLY CISPLATIN AND PACLITAXEL IN LOCALLY ADVANCED CARCINOMA CERVIX

Introduction:Carcinoma cervix is the most common gynaecological malignancy in women. Concurrent chemoradiotherapy is an effective treatment for locoregionally advanced squamous cell carcinoma of the cervix, with established benefits in both organ preservation and survival. Aims:1. To assess the immediate locoregional response rates of locally advanced squamous cell carcinoma of the cervix treated with concurrent chemoradiotherapy using weekly low dose cisplatin and low dose paclitaxel followed by HDR intracavitary brachytherapy. 2. To assess the acute toxicity. Materials and methods:This is a single arm prospective study in which 30 patients with cervical carcinoma of stages IB2-IIIB, presenting to our hospital, were given concurrent chemoradiation: EBRT 50Gy/25# with weekly Cisplatin 30mg/m2 and Paclitaxel 30mg/m2 followed by intracavitary brachytherapy 8Gy/2# and response was assessed, both clinical and radiological, at the end of 6 weeks after completion of therapy, using RECIST criteria. Toxicity was assessed using RTOG morbidity scoring. Results:Clinically, there was complete locoregional response in 27 patients (90%), partial response in 3 patients (10%). Acute toxicities were observed but they were manageable. Diarrhea presented as grade I, II and III in 5 (16.7%), 3 (10%) and 2 (6.7%) patients respectively. Grade Ihaematological toxicity was seen in 7 patients (23.3%) and grade II in 3 patients (10%) during the 5th week of chemo-radiation. Grade I and II skin reactions were seen in 7 patients (23.3%) with grade III reactions in one patient. Grade I bladder toxicity is seen is 2 patients (6.7%). Conclusion:This study shows including a taxane as a radiosensitiser, in the standard concurrent chemoradiation with weekly cisplatin schedule, yields better loco-regional response with acceptable toxicity, especially in locally advanced stages and those with pelvic nodal involvement.

Interfraction dose deviation and catheter position in cervical interstitial and intracavitary image guided HDR brachytherapy.

Interstitial and intracavitary gynecological HDR brachytherapy involve precise, localized delivery to targets with high dose gradients, sparing adjacent organs at risk (OAR). Due to the proximity of the rectum, bowel and bladder to the target, deviations in the applicator or catheter with respect to patient anatomy can significantly increase dose to OAR. The magnitude and direction of applicator and catheter migration at each fraction was assessed for template interstitial and tandem and ring (T&R) cohorts. The cohort included twelve gynecological patients with intact cervical lesions treated with external beam and brachytherapy. Pre-treatment CT images were registered to the simulation CT with respect to the target. Treatment catheter positions transformed into the planning CT coordinate system to evaluate localized catheter displacement and dose distributions calculated at each fraction. Dose was evaluated on the planning CT with planning contours and dwell locations at treatment position. Absolute deviation, depth and deflection angle for all patients were 4.6 ± 4.2 mm, -1.4 ± 4.0 mm, and 3.1 ± 2.3° respectively (n = 516 catheter positions for all treatment fractions and patients, mean ± SD). Absolute catheter deviation and deflection magnitude for interstitial treatments increased overall with each subsequent fraction with an overall increase of catheter retraction at each fraction (p < 0.005, n = 492 catheters, Kruskal-Wallis). A target EQD2 D90 reduction of 10 ± 10% and 7.7 ± 8.7% of the planned dose for interstitial and T&R cohorts respectively. There was an overall increase in bladder and rectal doses at each fraction. Catheter tracking in interstitial and intracavitary gynecological treatments with CT imaging revealed significant changes in catheter positioning with respect to the target volume. Overall deviations increased in magnitude with each subsequent fraction in the interstitial treatments. This caused patient dosimetry deviations, including target dose reduction and adjacent OAR doses changes.

A mathematical model to predict the different isodose volumes using TRAK value in HDR intracavitary brachytherapy for revised Manchester and ICRU-89 based Point A plans using computer tomography images

To find out the simple relationship between Total Reference Air Kerma (TRAK) and various isodose volumes. Calculated isodose volumes were compared with experimental data for revised Manchester and International Commission on Radiation Units and measurements (ICRU)-89 Point A-based treatment plans. The accuracy of the formula was compared with the results of other relationships available in the literature. Dosimetric data from 62 intracavitary brachytherapy (ICBT) treatment plans of 31 patients with cervical cancer were studied. Each patient had treatment plans normalized to revised Manchester and ICRU-89 Points A (Aflange and Aicru89). For each treatment plan, TRAK values, V350, V700, V1050, and V1400 were obtained. The modeling curve was plotted between Isodose volume (Vd) and the ratio of d/TRAK obtained from Aflange plans to get a mathematical relation. The results of this formula were compared with the experimental data and outcomes of other formulas available in the literature. A paired-sample t-test was performed to assess the statistical significance. In the case of revised Manchester-based Aflange normalization plans, the mean isodose volume of V350, V700, V1050, and V1400 were 285.98 ± 32.3 cm3, 101.96 ± 10.63 cm3, 52.71 ± 4.72 cm3, and 31.44 ± 2.33 cm3 respectively. Likewise, for ICRU-89 based Aicru89 normalization plans, the mean isodose volumes of V350, V700, V1050, and V1400 were 304.11 ± 26.17 cm3, 108.88 ± 8.29 cm3, 56.62 ± 3.69 cm3 and 34 ± 2.23 cm3 respectively. The mean difference was significant. The Mathematical relationship developed was [INLINE:1]. No correlation was found between TRAK and D0.1cm3,D2cm3 for organs at risk. The developed formula calculated isodose volumes within the accuracy of ± 3% in ICBT plans.

Correlation analysis of CT-based rectal planning dosimetric parameters with in vivo dosimetry of MOSkin and PTW 9112 detectors in Co-60 source HDR intracavitary cervix brachytherapy.

Intracavitary cervical brachytherapy delivers high doses of radiation to the target tissue and a portion of these doses will also hit the rectal organs due to their close proximity. Rectal dose can be evaluated from dosimetric parameters in the treatment planning system (TPS) and in vivo (IV) dose measurement. This study analyzed the correlation between IV rectal dose with selected volume and point dose parameters from TPS. A total of 48 insertions were performed and IV dose was measured using the commercial PTW 9112 semiconductor diode probe. In 18 of 48 insertions, a single MOSkin detector was attached on the probe surface at 50mm from the tip. Four rectal dosimetric parameters were retrospectively collected from TPS; (a) PTW 9112 diode maximum reported dose (RPmax) and MOSkin detector, (b) minimum dose to 2cc (D2cc), (c) ICRU reference point (ICRUr), and (d) maximum dose from additional points (Rmax). The IV doses from both detectors were analyzed for correlation with these dosimetric parameters. This study found a significantly high correlation between IV measured dose from RPmax (r = 0.916) and MOSkin (r = 0.959) with TPS planned dose. The correlation between measured RPmax with both D2cc and Rmax revealed high correlation of r > 0.7, whereas moderate correlation (r = 0.525) was observed with ICRUr. There was no significant correlation between MOSkin IV measured dose with D2cc, ICRUr and Rmax. The non-significant correlation between parameters was ascribable to differences in both detector position within patients, and dosimetric volume and point location determined on TPS, rather than detector uncertainties.

PHSOR03 Presentation Time: 10:10 AM: Practical Needle Placement and Dosimetry Improvements with Hybrid Intracavitary/Interstitial Ring Applicators

Purpose: Hybrid intracavitary/interstitial (IC/IS) applicators have been shown to improve local control for HRCTV > 30cc and dosimetry in all volume HRCTV compared to traditional intracavitary (IC) cervical HDR brachytherapy. Standard needle insertion patterns have not been well-established for hybrid IC/IS applicators. We quantify dosimetric benefits of the Vienna-style IC/IS applicator compared to IC-alone and aim to establish standard interstitial needle-loading and insertion depth patterns for non-bulky HRCTV.

Dosimetric and clinical outcomes of CT based HR-CTV delineation for HDR intracavitary brachytherapy in carcinoma cervix - a retrospective study.

Brachytherapy for carcinoma cervix has moved from Point A based planning to optimization of dose based on HR-CTV. Guidelines have been published by GEC ESTRO on HR-CTV delineation based on clinical gynecological examination and MR sequences. These have given significant clinical results in terms of local control. However, many centers around the country and worldwide still use CT based planning, which restricts HR-CTV delineation, as disease and cervix can rarely be differentiated on a planning CT. Various studies have been done to develop CT based contouring guidelines from the available data, but enough evidence is not available on the clinical outcome when treatment is optimized to HR-CTV contoured on CT images. The purpose of this study is to find out the relation between local control and dosimetry of HR-CTV as delineated on CT images. Patients of locally advanced carcinoma cervix treated radically with EBRT of 50 Gy in 25# and at least 4 cycles of concurrent weekly Cisplatin having a complete or partial response to EBRT were taken for study. All patients had completed CT based Intracavitary brachytherapy to 21 Gy in 3# of 7 Gy per # with dose prescription at point A and optimizing dose to reduce bladder and rectal toxicity. Follow up data on locoregional recurrence was obtained. HR-CTV delineation was done retrospectively on the treatment plan following guidelines by Viswanathan et al. EQD2 doses for EBRT+BT were calculated for point A and HR-CTV D90. The dosimetric data to HR-CTV and to Point A were then compared with patients with locoregional control and with local recurrence. 48 patients were taken, all had squamous cell carcinoma. The median age was 48 years. 33.33% were stage IIA, the rest were stage IIB. Median follow-up was 30 months with 25% developing recurrence of the disease. HR-CTV D90 EQD2 dose was significantly higher in patients with locoregionally controlled disease than in patients with local recurrence (83.97 Gy10 vs. 77.96 Gy10, p = 0.002). Patients with HR-CTV D90 EQD2 dose greater than or equal to 79.75 Gy 10 had better locoregional control than patients receiving dose less than 79.75 Gy10 (p = 0.015). Kaplan Meier plot for PFS showed significantly improved PFS for patients receiving HR-CTV D90 dose of at least 79.75 Gy10 (log-rank p-value = 0.007). Three year progression free survival was 87.1% in patients receiving HR-CTV D90 dose of at least 79.75 Gy10. CT based HR-CTV volume delineation with the help of pre brachytherapy clinical diagrams and MRI imaging may be feasible in a select subgroup of patients with complete or near-complete response to external beam radiation.

Feasibility of improving patient’s safety with in vivo dose tracking in intracavitary and interstitial HDR brachytherapy

PurposeThe in vivo dosimetric monitoring in HDR brachytherapy is important for improving patient safety. However, there are very limited options available for clinical application. In this study, we present a new in vivo dose measurement system with a plastic scintillating detector (PSD) for GYN HDR brachytherapy. MethodsAn FDA approved PSD system, called OARtrac (AngioDynamics, Latham, NY), was used with various applicators for in vivo dose measurements for GYN patients. An institutional workflow was established for the clinical implementation of the dosimetric system. Action levels were proposed based on the measurement and system uncertainty for measurement deviations. From October 2018 to September 2019, a total of 75 measurements (48 fractions) were acquired from 14 patients who underwent HDR brachytherapy using either a multichannel cylinder, Venezia applicator, or Syed-Neblett template. The PSDs were placed in predetermined catheters/channels. A planning CT was acquired for treatment planning in Oncentra (Elekta, Version-4.5.2) TPS. The PSDs were contoured on the CT images, and the PSD D90% values were used as the expected doses for comparison with the measured doses. ResultsThe mean difference from patient measurements was −0.22% ± 5.98%, with 26% being the largest deviation from the expected value (Syed case). Large deviations were observed when detectors were placed in the area where dose rates were less than 1 cGy/s. ConclusionsThe establishment of clinical workflow for the in vivo dosimetry for both the intracavitary and interstitial GYN HDR brachytherapy will potentially improve the safety of the patient treatment.

Multi-material 3D Printing in Brachytherapy– Prototyping Teaching Tools

The utilization of brachytherapy for cervical cancer has been declining, resulting in worsening survival. To improve resident confidence in performing of intracavitary and interstitial HDR brachytherapy procedures, an educational multi-material modular 3D printed gynecologic pelvic phantom training kit simulating both normal and pathological conditions has been developed. The implementation of this phantom in resident education is intended to allow for a more thorough and comprehensive training in tandem and ovoid and needle insertions. CT and MR scans from 50 patients with locally advanced cervical cancer were analyzed. Dimensions of the uterine bodies and canals were measured from the T2 weighted MRI images. These measurements were used to construct four model uteri based off of averages and standard deviations. The vaginal canal was constructed based on standard gynecological speculum dimensions. Individual STL files were imported into Autodesk Meshmixer and manipulated to include features such as hollowed out cavities and canals to allow for applicator placement. Modular components of the phantom were designed and integrated into patient anatomy using CAD 3DShapr. Five HRCTVs were extracted from patient scans to be incorporated into the uterine body. Elasticity properties of tissues were used to calculate appropriate flexible and rigid shore values (0-100) to assign to each anatomical structure for multi-material printing. Average dimensions and SD from the 50-patient study are presented in Table 1 for the anatomical structures considered. The finalized prototype kit consists of three anteverted uteri based on the smallest, the average, and the largest dimensions from our patient set. The fourth uterus is retroverted and uses average dimensions. Clip-on HRCTV attachments expanding outside of the uterine body are included to mimic different pathology. Color staining with different shore values within the uterus was done to represent internal HRCTVs. All uterus bodies and the vaginal canal were printed using Agilus (shore 30A) in clear as a means of evaluation for tandem/ovoid and needle placement. The rectum and HRCTVs were printed using a blend of polymers that allow for variable stiffness (Vero and Agilus, shore 70A and 40A respectively). The bladder was printed using pure Agilus (shore 30A). A multi-material modular 3D printed pelvic phantom training kit simulating normal and cervix pathological conditions has been developed for practicing tandem and ovoid insertions. This tool may be used to help address a gap in decreased resident confidence in performing brachytherapy procedures.Tabled 1Abstract 2983; TableCanal Length [cm]Canal Width [cm]Body Length [cm]Body Width (top) [cm]Body Width (midpoint) [cm]Canal Angle [deg]U15.810.345.812.023.1519.1U26.230.427.872.744.4527.6U37.630.3439.933.455.7436.1U4*6.230.427.872.744.4527.6∗Retroverted Open table in a new tab

Preliminary exploration of 3D printed individualized applicator for 3D-image-guided intracavitary HDR-brachytherapy for nasopharyngeal carcinoma

Objective To explore the feasibility of 3D printed individualized applicator for the intracavitary HDR-brachytherapy for nasopharyngeal carcinoma. Methods CT scan was performed in 1 case of recurrent rT1 nasopharyngeal carcinoma and 1 case of T2 residual nasopharyngeal carcinoma and the obtained images were transmitted to 3D image processing software. The geometric contour parameters of the nasopharyngeal cavity were obtained and a pipeline was designed to make it close to the recurrent gross tumor volume (rGTV). Individualized cavity applicators were created by using 3D printer. The applicator was inserted into the patient′s nasopharyngeal cavity through oral cavity. The source tube and false source were inserted into the preset pipe of the applicator. CT scan was performed again and the images were transmitted to the 3D brachytherapy planning system. After delineating the target volume and organ at risk, treatment plan was optimized. After completing the first treatment, the applicator was removed. Before second treatment in a few days, CT scan was reviewed to confirm whether the position was correct. Results When the applicator was inserted into the nasopharyngeal cavity, it could be fully aligned with the nasopharyngeal wall and self-fixed without additional fixation measures. Comparing the location of false source in multiple reviews of CT scan, the error was ≤1 mm. No significant discomfort was reported throughout the treatment. In optimized three-dimensional treatment, 100% prescription dose curve included the full rGTV, maximum dose of the brain stem and spinal cord was<30% prescription dose. Recurrent patients were given with a prescription dose of DT 40Gy/8 fractions/4 weeks and patients with residual tumors were given with 12Gy/2 fractions/1 week. No tumor recurrence was observed at postoperative 3 months in two cases. Conclusions The 3D printed individualized nasopharyngeal intracavitary applicator has the advantages of self-fixation, accurate location, good repeatability and good patient tolerance. The short-term outcome is effective, whereas its long-term clinical effect and adverse reactions need to be further observed. Key words: 3D printed; Individualized applicator; Nasopharyngeal neoplasm/intracavitary radiotherapy

Formulation of normal tissue irradiation volumes in Co-60 and Ir-192 HDR ICBT of Ca cervix using Total Reference Air Kerma (TRAK).

The aim of this study was to formulate isodose volume relations encompassed by isodose surfaces in Co-60 and Ir-192 HDR intracavitary brachytherapy (ICBT) of cervix carcinoma using the Total Reference Air Kerma (TRAK). The TRAK and isodose volumes are radioactive source related. The formulated relations can easily estimate the irradiated isodose volume if the TRAK and dose are known. The C0-60 can also be used for brachytherapy because of its longer half life and comparable OAR doses to Ir-192. Isodose volumes encompassed by different isodose surfaces and TRAK were obtained from 22 Ca cervix ICBT treatment plans in Co-60 and Ir-192 HDR brachytherapy with 9Gy prescription to point A. Isodose volume relations were formulated both for Co-60 and Ir-192 brachytherapy source from the slopes and intercepts of the linear fit in the plot between isodose volumes and TRAKs. The TRAK value of Co-60 was higher than Ir-192 by about 7.16%. The isodose volumes at low doses for Co-60 were higher than Ir-192. But no significant differences in the dose to the bladder and rectum were observed due to these sources. For dose to 2cm3 bladder and rectum volume, the differences were 1.07% and 0.75%, respectively. The correlation coefficient with the 2-tailed significance of correlation (p value) between TPS measured isodose volume and calculated isodose volumes using the formulated relations at different dose values were statistically significant as p<0.05. Results show different isodose volumes for both sources but the dose to the bladder and rectum are nearly the same.