Multichannel Vaginal Cylinder Research Articles

Quantification of Artifacts and Image Distortions in 1.5 Tesla Magnetic Resonance Images of a Commercial Multi-Channel Vaginal Cylinder Brachytherapy Applicator Set.

The BEBIG Portio multi-channel applicator provides better target dose coverage and sparing organs-at-risk compared to a single-channel cylinder. However, artifacts and distortions of Portio in magnetic resonance images (MRI) have not yet been reported. We aimed to quantify the artifacts and distortions in its 1.5-Tesla MR images before clinical use. In this experimental study, we employed a gelatin-filled phantom to conduct our measurements. T2-weighted (T2W) images were examined for artifacts and distortions. Computed tomography (CT) images were used as a reference to assess image distortions. Artifact severity was measured by recording the full-width-at-half-maximum (FWHM) image pixel values at various positions along the length of the applicator/channels. CT and MRI-based applicator reconstruction accuracy were then compared, and signal-to-noise ratio (SNR) and contrast were also determined for the applicator images. The applicator distortion level for the Portio applicator was less than the image spatial resolution (0.5±0.5 pixels). The average FWHM for the tandem applicator images was 5.23±0.39 mm, while it was 3.21±0.37 mm for all channels (compared to their actual diameters of 5.0 mm and 3.0 mm, respectively). The average applicator reconstruction difference between CT and MR images was 0.75±0.30 mm overall source dwell positions. The image SNR and contrast were both acceptable. These findings indicate that the Portio applicator has a satisfactory low level of artifacts and image distortions in 1.5-Tesla, T2W images. It may, therefore, be a promising option for MRI-guided multi-channel vaginal brachytherapy.

Outcomes of 3D MRI Based HDR Brachytherapy with Hybrid Multichannel Vaginal Cylinder Applicator and Freehand Needles for Treatment of Vaginal Disease

<h3>Purpose/Objective(s)</h3> Multichannel vaginal cylinder (MCVC) is unable to cover residual vaginal cancer >7 mm thick or with supra-vaginal extension. Freehand needles inserted directly into areas of disease can extend isodose lines to allow for better coverage of disease if clinically indicated. We report outcomes of use of MCVC with freehand needles at our institution. <h3>Materials/Methods</h3> All patients with malignancies involving vagina treated from 2014-2021 with HDR BT at our institution with MCVC with freehand needles were identified. Clinical characteristics including primary malignancy, initial stage, date of diagnosis and recurrence (if applicable), prior RT, use of EBRT, and BT dose and fractionation were collected. Number of freehand needles used per fraction, 3D imaging used for planning, high-risk clinical target volume (HR-CTV) at each fraction, dose to 2cc (D2cc) of organs at risk, and HR-CTV D90 were recorded. Initial response based on examination and imaging and overall local control outcomes were recorded. Local failure was defined as time to recurrence either within HR-CTV or marginal failure, calculated from date of last BT fraction, with censorship at date of last follow-up. Local control was analyzed via Kaplan-Meier method. <h3>Results</h3> 33 patients were identified with median follow-up 1.9 years (IQR 1.0-2.9 years). 19 patients (57.6%) had primary endometrial cancer with vaginal recurrence/disease. Remaining patients had primary vaginal cancer or involvement secondary to other primaries. 8 patients had recurrent disease after previous course of RT. 24 patients received EBRT with median dose of 45 Gy in 25 fractions, with remaining patients treated with BT alone. BT prescription dose ranged from 20-36 Gy in 3-7 fractions, with a total of 168 BT fractions delivered. Median number of freehand needles utilized was 3, with freehand needles utilized in 157/168 total fractions. MRI-based plan was done for at least 1 fraction in 30 patients (90.9%). Median HR-CTV at time of BT was 19.7cc. Median D2cc to the bladder, rectum, and sigmoid were 56.4 Gy, 55.7 Gy, and 45.4 Gy, respectively. Median D90 to the HR-CTV for pts treated with EBRT plus BT was 76.7 Gy and for BT alone was 48.8 Gy. 29 patients (87.9%) had complete local response to BT on initial examination and/or follow-up imaging. 1 and 2-year local control rates for those who did not have prior RT was 89.5% and 89.5%, respectively. 1 and 2-year local control rates for those who had previous RT was 58.3% and 29.2%, respectively. 1 patient had vaginal laceration requiring surgical repair and 1 patient with disease progression developed small bowel obstruction 1 month after BT, with no additional acute grade 3+ toxicities identified. <h3>Conclusion</h3> Our approach with MCVC plus freehand needles with MRI-based planning was feasible and safe. Initial local response is excellent, with acceptable local control rates and low rate of serious acute toxicities. Multi-institutional experiences are needed to further validate this approach for treatment of vaginal disease.

Application of 3D Printed Multi-Channel Vaginal Cylinder for Vaginal Brachytherapy in the Cervical Cancer Invading the Middle and Lower Thirds of Vagina

<h3>Purpose/Objective(s)</h3> Patients with cervical cancer invading the middle and lower thirds of vagina (CCIV) had high recurrence rates and worse prognosis. Single-channel vaginal cylinder (SCVC) could make the dose curve wrap completely around the high-risk clinical target volume (HRCTV) for CCIV patients. However, the dose of HRCTV and organs at risk (OARs) would increase at the same time for symmetrical dose distribution of SCVC dose curve, especially in patients with eccentric distribution of the tumor. It was still difficult to achieve a conformal target dose distribution when the SCVC's lead block was used for protecting the OARs. The 3D printed multi-channel vaginal cylinder (3D-MCVC) could arrange the radioactive source according to the tumor location. But there was very little foundation in the literature on dose contrasting in SCVC and MCVC for brachytherapy in CCIV. Therefore, this study proposed to confirm that 3D-MCVC brachytherapy (3D-MCVCB) was better than SCVCB to reduce the OARs dose and achieved conformal target dose distribution. <h3>Materials/Methods</h3> All patients were given the dose of 28Gy/4fraction/4week for brachytherapy. According to ICRU89 document, HRCTV and OARs (the bladder, rectum, and sigmoid colon) were contoured on the CT images in the Nuclear 3D brachytherapy radiotherapy treatment planning system. By self-control study, a simulation plan for the SCVCB was matched while making a 3D-MCVCB plan. The two plans of OARs doses (D_2cc, D_1cc, D_0.1cc) and HRCTVD₉₀ were divided into 3D-MCVCB groups and virtual SCVCB groups, separately. The statistical analysis was the paired sample t-test. <h3>Results</h3> From October 2018 to May 2021, 16 patients of CCIV were included. 128 plans were made for two groups. The prescription dose for HRCTV was 7Gy/1f. When HRCTVD₉₀ was almost 7Gy in the virtual SCVCB group, the doses of OARs were roughly at the threshold of dose limiting. However, when HRCTVD₉₀ of 3D-MCVC group was 7.45±0.47Gy, all OARs doses of 3D-MCVCB group were lower than them of SCVCB group, (P<0.05) (Table1). <h3>Conclusion</h3> The empirical findings in this study provided a new understanding that 3D-MCVCB achieved more conformal target dose distribution for CCIV patient. 3D-MCVCB could better maximize the dose to target tissues and minimize the dose to organs at risk (OARs) than SCVCB. Furthermore, the clinical efficacy and adverse reactions need to be further studied. Table 1. Doses given for HRCTVD₉₀ and OARs for the whole group of plans (n = 128)

Outcomes of 3D MRI based HDR brachytherapy with hybrid multichannel vaginal cylinder applicator and freehand needles for treatment of vaginal disease

Freehand needles can be used with multichannel vaginal cylinders (MCVC) to cover vaginal cancer >7 mm thick or with supra-vaginal extension. We report our institutional outcomes using this novel hybrid technique.Patients with vaginal malignancies treated with HDR BT using MCVC plus freehand needles from 2014-2021 at our institution were identified. Clinical characteristics, details of brachytherapy, initial response, and overall local control (LC) outcomes were recorded. LC was analyzed via Kaplan-Meier method.34 patients were identified with median follow-up 1.9 years. 19 patients had primary endometrial cancer with vaginal recurrence/disease, and remaining had primary vaginal cancer or other primaries. 7 patients had recurrence after previous RT course. 25 patients received EBRT with median dose 45 Gy in 25 fractions, and rest received BT alone. Median HR-CTV D90 for patients treated with EBRT plus BT was 77.4 Gy.30 patients had complete local response to BT on initial examination and/or follow-up imaging. 1 and 2-year LC rates in patients without prior RT treated with EBRT + BT were 94.1% and 94.1%, respectively. 1 and 2-year LC rates for those without prior RT were 88.1% and 76.4%, respectively. 1 and 2-year LC rates for those with prior RT were 68.6% and 34.3%, respectively. 1 patient had vaginal laceration requiring surgical repair, and 1 patient developed small bowel obstruction 1 month after BT, with no additional acute grade 3+ toxicities identified.Our approach with MCVC plus freehand needles with MRI-based planning was feasible and safe, with excellent initial local response and low rate of serious toxicities.

Technical note: Commissioning of an ultrasound-compatible surrogate vaginal cylinder for transvaginal ultrasound-based gynecologic high-dose-rate brachytherapy.

To provide a comprehensive set of commissioning tests for clinical implementation of three-dimensional transvaginal ultrasound (3D TVUS) as a replacement of computed tomography (CT) for applicator reconstruction in gynecologic (GYN) intracavitary high-dose-rate brachytherapy (HDRBT) with a multi-channel vaginal cylinder (MCVC). We introduce an ultrasound-compatible "surrogate" vaginal cylinder (SVC) for reconstruction of Elekta's CT-MR Multi Channel Applicator (MCVC) in 3D TVUS. The MCVC is digitized over the SVC in 3DUS using digital library model overlay. Consulting guidelines from various sources (CPQR, GEC-ESTRO, AAPM), we identify and describe three tests specific to commissioning the SVC: (1) verification of SVC outer dimensions, (2) source position accuracy of MCVC digitization over the SVC in 3D TVUS, and (3) MRI/US registration error. The SVC outer dimensions (diameter and A-D marker locations) were well matched to the MCVC, however a 0.6mm discrepancy in length between cylinder tips was observed. Source position accuracy was within 1mm (tolerance recommended by CPQR) when reconstructing the MCVC in 3D TVUS. Dice similarity coefficients and target registration error for MRI/3D TVUS registration was similar to MRI/CT registration, which is the clinical standard. These commissioning tests are performed using institutional equipment but provide the framework for any practitioner to repeat in their own setup, to demonstrate safe adoption of the 3D TVUS system for patient treatments. We demonstrate that MRI/US-based workflow achieves similar source position accuracy and image registration error as standard MRI/CT, which is consistent with standard tolerances. This is a critical step toward replacement of CT with US in GYN HDRBT treatments with the MCVC.

Dosimetric study of Varian Universal Multi-Channel Cylinder System for High-Dose-Rate 192Ir Brachytherapy

Recently, the Varian multichannel vaginal cylinder (MCVC) set for high-dose-rate 192Ir brachytherapy was commercially released. This MCVC was distinct from our existing MCVC in its peripheral channel layout and tip design. This investigation sought to assess the dosimetric impact of these changes. The dimensions of the virtual model for each applicator were compared against both physical and radiographic measurements. Volumetric dose distributions were generated in silico using a model-based dose calculation algorithm (MBDCA). To characterize the effects of the new peripheral channel layout on dose to adjacent areas ("dose-spill"), point doses were compared using two sets of applicator-based reference points: at surface or 5 mm radially from surface. To evaluate the dose-shaping capabilities, a dose distribution was generated for the new applicator and assessed against a representative dose distribution for a patient previously treated with existing equipment. Based on both physical and radiographic measurements, virtual models were representative of each applicator within ±1 mm. Commissioning of the MBDCA was benchmarked based on AAPM Working Group on Dose Calculation Algorithms in Brachytherapy. The layout of the new applicator reduced dose-spill to other reference points significantly, as much as a factor of 16.3, compared with the existing equipment. The rounded tip shape and curve of the peripheral channels in the new applicator produced more conformity to its HR-CTV than existing equipment. Compared with our existing equipment, the design changes in the new Varian MCVC set offered improved control of dose spill and better conformality to HR-CTV.

PO33: Institutional Experience of 3D MRI Based HDR Brachytherapy with Hybrid Multichannel Vaginal Cylinder Applicator and Freehand Needles for Treatment of Vaginal Disease

Purpose: Multichannel vaginal cylinder (MCVC) by itself is not sufficient to cover residual vaginal cancer more than 7 mm thick or with supra-vaginal extension. Freehand needles inserted directly into areas of disease can be utilized to extend isodose line to allow for better coverage of disease extent if clinically indicated. We sought to report initial outcomes of use of MCVC with freehand needles at our institution.

PO26: Individualized Vaginal Boost Brachytherapy: Dosimetric Lessons with the Multichannel Vaginal Cylinder

Purpose: Measurable tumors that involve vaginal tissue, including primary vaginal cancer and recurrent endometrial cancer (after prior hysterectomy), are often treated using a combination of external beam radiotherapy (EBRT) and fractionated high-dose-rate (HDR) brachytherapy (BT). BT boost may be achieved with a variety of applicator types, mainly intracavitary (IC) single channel (SCVC) or multichannel vaginal cylinder (MCVC), or an interstitial (IS) implant. In comparison to SCVC, MCVC features an arrangement of peripheral catheters that allow preferential treatment of localized surface targets to higher doses, without the need for an invasive IS component.

PO29: Acceptance and Implementation of the Oncentra Applicator Model Library for Automatic Catheter Reconstruction in Multichannel Vaginal Cylinder Applicators

Purpose: This work presents the acceptance, evaluation and implementation of a virtual applicator model library for automatic catheter reconstruction of multichannel vaginal cylinder (MCVC) applicators using the Oncentra applicator model library. The library contains cylinder models that can be used directly with patient's treatment planning CT in the Oncentra Brachytherapy Treatment Planning System.

PO33: Institutional Experience of 3D MRI Based HDR Brachytherapy with Hybrid Multichannel Vaginal Cylinder Applicator and Freehand Needles for Treatment of Vaginal Disease

PO33: Institutional Experience of 3D MRI Based HDR Brachytherapy with Hybrid Multichannel Vaginal Cylinder Applicator and Freehand Needles for Treatment of Vaginal Disease

PO27: A Dosimetric Comparison between Rounded-Tip vs Flat-Tip Multichannel Applicators for Recurrent Endometrial Cancer Involving Vaginal Apex

Purpose: The latest multichannel vaginal cylinder applicator (MCA) offered by our afterloader vendor incorporates a rounded apical tip (MCAR) design, whereas the previous model was designed with a flat tip (MCAF). We investigated the dosimetric implications of these different MCA tip designs with an illustrative case study.

Adjuvant brachytherapy for FIGO stage I serous or clear cell endometrial cancer

ObjectivesOptimal adjuvant treatment for early-stage clear cell and serous endometrial cancer remains unclear. We report outcomes for women with surgically staged International Federation of Gynecology and Obstetrics (FIGO) stage I...

Development of an indigenous low-cost multichannel cylinder applicator for vaginal tumors

PurposeThe purpose of this study was to report our experience regarding the development of a low-cost multichannel vaginal cylinder applicator for superficial and recurrent vaginal tumors. Methods and MaterialsThe applicator mold was created by applying heated wax sheets in layers around a plastic tube. Interstitial stainless-steel needles were placed at equal distance around the mold surface to create multiple channels for treatment. Two plans were created using CT images for a patient with a recurrent tumor over the posterior vaginal wall for comparing single-channel and multichannel cylinder dosimetry. The doses received by the target (high risk clinical target volume) and organs at risk (OARs) were computed using dose–volume histograms. ResultsThere was no significant difference in terms of the prescribed dose delivered to high risk clinical target volume between the two plans. The volume of the target receiving 150 and 200 percent (V150 and V200) dose was higher in the multichannel cylinder plan than the single-channel cylinder plan. In terms of doses to the OARs, there was no significant difference between the rectum doses (D2cc rectum). There was a significant reduction in the dose to the bladder (D2cc bladder), urethra (D0.1cc urethra), and uninvolved vagina (D2cc uninvolved vagina). ConclusionsMultichannel vaginal cylinders reduce doses to the OARs as compared with the single-channel vaginal cylinder in superficial vaginal lesions limited to the wall of the vagina. Their use is limited by the cost of the applicator. Our low-cost multichannel vaginal cylinder can be used as a reliable alternative in such situations.

Clinical Practice Pattern Of Adjuvant Vaginal Brachytherapy In Early-stage Endometrial Carcinoma According To ESMO-ESGO-ESTRO Risk Classification: Long-term updated Data From A Multi-institutional Analysis In China

To evaluate the clinical practice pattern of adjuvant vaginal brachytherapy (VBT) in early-stage endometrial carcinoma (EC) according to ESMO-ESGO-ESTRO risk classification in China from long-term updated data of a multi-institutional analysis. We retrospectively evaluated clinical data of patients with early-stage EC at 13 institutions in China between 2000 and 2015. Eligibility requirements included the primary hysterectomy/bilateral salpingo-oophorectomy and adjuvant radiotherapy, stage I and II disease (FIGO 2009 staging), and complete clinicopathologic and follow-up information. All patients were divided into low-risk (LR), intermediate-risk (IR), high-intermediate risk (HIR) and high-risk (HR) groups according to ESMO-ESGO-ESTRO risk classification. We evaluated clinical practice pattern and tendency of VBT in different risk groups during various periods. Proportions were compared by using the Chi square test for values of 5 or higher and with Fisher’s exact test for values of less than 5. All data were examined using statistical analysis software. A total of 1268 early-stage patients were reviewed and 1108 cases with intact data were included in the analysis. The median follow-up time was 53 months (range 6–207 months). The median age was 56 years (range 23–86 years). Stage Ia/b disease represented 86.0% of the cohort, HR patients 22.9%, HIR patients 20.0%, IR patients 29.2%. Patients received VBT alone (43.2%, n = 479), EBRT alone (14.3%, n = 158), EBRT+VBT (42.5%, n = 471), and chemotherapy (22.9%, n = 235). In HR and HIR groups, the proportion of VBT alone increased 33.3% (0 vs. 33.3%) and the proportion of VBT boost after EBRT decreased 10.5% (61.3% vs. 50.8%) from 2000 to 2015. In IR and LR groups, VBT alone increased 61.7% (4.7% vs. 66.4%) and VBT boost decreased 29.4% (51.6% vs. 22.2%) in the corresponding period. All institutions commonly use High-dose-rate(HDR) VBT. The commonly used applicators include the multichannel vaginal cylinder (77.7%), single channel vaginal cylinder (16.7%) and ovoids (5.6%). A fixed 3-4cm length of the proximal vagina was reported by 62.9%, a proximal 1/3-1/2 length of the vagina by 36.2%, and Entire vagina by 0.8%. Specify dose: 77.7% specify to 0.5-cm depth from the vaginal surface, and 22.3% specify elsewhere. There were 11 and 13 different dose-fractionation schedules for VBT alone and VBT boost, respectively. The most common fractionation for VBT alone and VBT boost is 5 Gy for six fractions and 5 Gy for two fractions, both to 0.5-cm depth. Our study provides an assessment of clinical practice pattern for adjuvant VBT management of early-stage EC in China. Historical data demonstrate that the clinical practice of adjuvant VBT alone increased significantly in different risk classification groups over the past 15 years, especially in IR to HR groups.

An innovative gynecological HDR brachytherapy applicator system for treatment delivery and real-time verification

The multichannel vaginal cylinder (MVC) applicator employed for gynecological high dose rate (HDR) brachytherapy increases dose delivery complexity, and thus makes the treatment more prone to errors. A quality assurance (QA) procedure tracking the source throughout dose delivery can detect dwell position and time errors in the multiple channels of the applicator.A new MVC system with integrated real time in vivo treatment delivery QA has been developed based on diodes embedded on the outer surface of the MVC. It has been pre-calibrated and verified using a non-clinical treatment plan with consecutive test positions and dwell times within each catheter, followed by the delivery of ten clinical plans of adjuvant vaginal cuff brachytherapy following hysterectomy for endometrial cancer.The non-clinical verification showed overall mean dwell position and time discrepancies between the nominal and measured treatment of −0.2 ± 0.5 mm and −0.1 ± 0.1 s (k = 1), respectively. The clinical plans showed mean positional discrepancies of 0.2 ± 0.4 and 0.0 ± 0.8 mm, for the central and peripheral catheters, respectively, and mean dwell time discrepancies of −0.1 ± 0.2 and −0.0 ± 0.1 s for central and peripheral catheters, respectively.The innovative prototype of the MVC system has shown the ability to track the source with sub-mm and sub-second accuracy, and demonstrated potential for its incorporation into the clinical routine.

Image-based Multichannel Vaginal Cylinder Brachytherapy for the Definitive Treatment of Vaginal Cancers

Brachytherapy (BT) is integral to vaginal cancer treatment and is typically delivered using either an intracavitary single-channel vaginal cylinder or an interstitial BT (ISBT) applicator. Multi-channel vaginal cylinder (MCVC) applicators allow for improved organ-at-risk (OAR) sparing compared to single-channel applicators while maintaining target coverage and avoiding ISBT implantations in selected patients (pts). We present clinical outcomes of pts treated with image-based high-dose-rate (HDR) BT using a MCVC. Sixty pts with vaginal cancer (27% primary vaginal and 73% recurrence from gynecologic primaries) were treated with combination external beam radiotherapy (EBRT) and image-based HDR BT utilizing MCVC from 2011 to 2016. Pts were selected for treatment with MCVC only if residual disease thickness was ≤7 mm after EBRT. The BT high-risk clinical target volume (CTVHR) included the circumferential vaginal surface as defined by the length of the pre-EBRT gross tumor volume (GTV) from both imaging and clinical examination, and the post-EBRT GTV defined the area for which the entire thickness of the vagina and residual tumor would be included. Total EBRT and BT doses were summated and converted to equivalent dose in 2 Gy fractions (EQD2 Gy). All pts received 3D image-based BT to a total equivalent dose of 70-80 Gy. Nineteen pts (32%) received concurrent chemotherapy with EBRT, and 7 (12%) received adjuvant systemic therapy. After a median follow-up of 45 months (range, 11-78), complete clinical response was documented in 98% of pts. The median CTVHR volume was 24.4 cc (interquartile range [IQR], 14.1), with a median dose delivered to 90% of CTVHR of 77.2 EQD2 Gy (IQR, 2.8). The 4-year local-regional control (LRC), distant control, disease-free survival, and overall survival rates were 92.6%, 76.1%, 64.0%, and 67.2%, respectively. There were no significant differences in LRC by any of the examined patient and treatment factors. The 4-year LRC rates were similar between the primary vaginal (92%) and recurrent (93%) groups (p=0.290). Pts with lymph node positive disease had a lower rate of distant control at 4 years (22.7% vs. 89.0%, p<0.001). There were no Grade 3 or higher acute complications. The 4-year rate of late Grade 3 or higher toxicity was 2.7%. One patient developed a severe small bowel toxicity manifested as adhesions of the terminal ileum 13 months after treatment. Clinical outcomes of pts with primary and recurrent vaginal cancer treated definitively in a systematic manner with combination EBRT with image-guided HDR BT utilizing a MCVC applicator demonstrate high rates of local control and low rates of severe morbidity. The MCVC technique allows interstitial implantation to be avoided in select pts with ≥7 mm residual disease thickness following EBRT while maintaining excellent clinical outcomes with extended 4-year follow-up in this rare malignancy.

Image-based multichannel vaginal cylinder brachytherapy for the definitive treatment of gynecologic malignancies in the vagina

PurposeBrachytherapy is integral to vaginal cancer treatment and is typically delivered using an intracavitary single-channel vaginal cylinder (SCVC) or an interstitial brachytherapy (ISBT) applicator. Multi-channel vaginal cylinder (MCVC) applicators allow for improved organ-at-risk (OAR) sparing compared to SCVC while maintaining target coverage. We present clinical outcomes of patients treated with image-based high dose-rate (HDR) brachytherapy using a MCVC. Methods and materialsSixty patients with vaginal cancer (27% primary vaginal and 73% recurrence from other primaries) were treated with combination external beam radiotherapy (EBRT) and image-based HDR brachytherapy utilizing a MCVC if residual disease thickness was 7 mm or less after EBRT. All pts received 3D image-based BT to a total equivalent dose of 70–80 Gy. ResultsThe median high-risk clinical target volume was 24.4 cm3 (interquartile range [IQR], 14.1), with a median dose to 90% of 77.2 Gy (IQR, 2.8). After a median follow-up of 45 months (range, 11–78), the 4-year local-regional control, distant control, DFS, and OS rates were 92.6%, 76.1%, 64.0%, and 67.2%, respectively. The 4-year LRC rates were similar between the primary vaginal (92%) and recurrent (93%) groups (p = 0.290). Pts with lymph node positive disease had a lower rate of distant control at 4 years (22.7% vs. 89.0%, p < 0.001). There were no Grade 3 or higher acute complications. The 4-year rate of late Grade 3 or higher toxicity was 2.7%. ConclusionsClinical outcomes of pts with primary and recurrent vaginal cancer treated definitively in a systematic manner with combination EBRT with image-guided HDR BT utilizing a MCVC applicator demonstrate high rates of local control and low rates of severe morbidity. The MCVC technique allows interstitial implantation to be avoided in select pts with ≤7 mm residual disease thickness following EBRT while maintaining excellent clinical outcomes with extended 4-year follow-up in this rare malignancy.

Image-Guided Multi-Channel Cylinder Brachytherapy for Gynecologic Cancers Involving the Vagina: Initial Experience with Vaginal Dose-Volume Parameters

Image-guided high-dose-rate multichannel vaginal cylinder (MCVC) brachytherapy (BT) permits conformal dose delivery to a vaginal tumor while sparing surrounding organs-at-risk. Due to the proximity of the peripheral channels to the tumor and cylinder surface, the adjacent vaginal mucosa is a dose-limiting structure when using MCVC, however, specific dose-volume limitations are not well characterized. We explored vaginal dose-volume parameters in a series of consecutive patients treated with MCVC for gynecologic cancers involving the vagina.

Differences in urethral dosimetry between CT and MR imaging in multichannel vaginal cylinder brachytherapy

PurposeIn image-based brachytherapy (IBBT), the dosimetry of small structures may be particularly sensitive to changes in contouring between imaging modalities. We therefore sought to characterize differences in urethral dosimetry in vaginal brachytherapy based on contouring on MRI vs. CT. Methods and MaterialsWe retrospectively identified our most recent 15 patients treated with intracavitary brachytherapy for distal vaginal malignancies. On T2-weighted MRI, both the lumen and urethral wall were contoured. On CT, the urethral lumen alone was contoured, as the wall is indistinguishable from surrounding tissue. High-dose-rate (HDR) IBBT plans were generated for all patients. ResultsMean urethral volume was higher on MRI than CT at 3.7 cc vs. 1.1 cc (p < 0.0005). As a result, there were statistically significant increases on MRI in D0.1cc and D0.5cc, as well as EQD2 D0.1cc and EQD2 D0.5cc when applied to a full course of treatment (45 Gy EBRT + 25 Gy IBBT). ConclusionsWe have quantified the expected differences in urethral volume and dosimetry when contoured on MRI vs. CT. Inclusion of the urethral wall on MRI, with its average thickness of 2.2 mm, likely more accurately reflects the true organ at risk and results in an increase in reported dose compared to CT.

Dosimetric comparison of interstitial brachytherapy with multi-channel vaginal cylinder plans in patients with vaginal tumors

BackgroundTo evaluate the dosimetric performance of multi-channel vaginal cylinder (MCVC) against interstitial brachytherapy (ISBT) for the treatment of vaginal tumors.MethodsVaginal tumors with extension of > 0.5 cm and ≤ 2 cm from the lateral vaginal wall and/or ≤ 1 cm in height above the vaginal vault were retrospectively selected from a ISBT registry trial database. The selected patients were treated with ISBT and targets included the intermediate (IRCTV) or high-risk (HRCTV) clinical target volumes. For technique comparison, a 35 mm MCVC was registered with the interstitial intra-vaginal cylinder. Bladder and rectum contours were transferred from the ISBT to the MCVC-BT plans. Vaginal mucosa was achieved by 3 mm uniform expansion from cylinder surface. Both the ISBT and MCVC-BT plans were optimized using the Inverse Planning Simulated Annealing optimization algorithm. After normalizing target D90 to 700 cGy, dose to organs at risk were measured and compared between ISBT and MCVC plans.ResultsSix interstitial patient plans met the inclusion criteria for this study. Four patients had vaginal primaries and two recurrent cancers in the vagina. Lower doses to bladder and rectum were seen with ISBT plans. In half of the MCVC plans, the rectal dose met the recommended constraints. For plans in which the rectal constraint was not met, the target volumes were abutting the rectum and had a cranial-caudal length ≥ 5 cm. Dose to vaginal mucosa was lower in ISBT plans directed to the HRCTVs, although no difference was seen in circumferential IRCTVs.ConclusionsOverall, ISBT results in decreased dose to OARs as compared to MCVC. However, MCVC BT results in acceptable doses to OARs with possible improvement in vaginal doses for circumferential targets. Careful consideration to tumor geometry and location may help guide optimal techniques in vaginal tumor brachytherapy.