Magnetic resonance–guided interstitial therapy for vaginal recurrence of endometrial cancer

KORTUC, a novel hydrogen peroxide‑based radiosensitizer for the enhancement of brachytherapy in patients with unresectable recurrent uterine cervical cancer

Kochi Oxydol Radiation Therapy for Unresectable Carcinoma (KORTUC) is a novel radiosensitizer invented by Professor Ogawa at Kochi University (Japan) in 2006. The current study aimed to report the experience of the present authors with the use of KORTUC treatment in combination with interstitial brachytherapy (ISBT), with or without external beam (EB) radiotherapy (RT), in patients with locally recurrent cervical cancer (LRCC), who were likely to have a high risk of poor prognosis. Between April 2012 and January 2020, 14 female patients (15 tumoral lesions) with LRCC underwent KORTUC with ISBT. Their previous treatments included surgery (n=4), radiation therapy (n=8) and surgery plus RT (n=3). The primary lesions were located in the vaginal stump (n=5), pelvic wall (n=3), cervix (n=3), vaginal wall (n=2) and lymph nodes (n=2). At 2 h before RT, KORTUC was injected intratumorally via direct colposcopy. The dose of KORTUC ranged from 4-12 ml, adjusted for the tumor size. For patients who underwent ISBT, KORTUC was administered before and after insertion of the applicator before irradiation. Intratumoral injection of KORTUC was completed without any technical or safety issues in all 15 patients; it was well tolerated with no adverse events observed. KORTUC also showed preferable efficacy; a clinical complete response was observed in 87% of patients and the initial response rate was 100%. The 2-year local control rate in patients who underwent ISBT + KORTUC was 79%, whereas it was 63% in the re-irradiation group which was significantly lower (P=0.02) than that in the non-irradiation group (100%). Based on this finding, KORTUC with external irradiation is considered to be an optimal treatment strategy for patients with newly diagnosed LRCC this disease. Additionally, KORTUC may be an effective radiation response enhancer in multiple cancer types in which locoregional control after RT alone remains poor.

A novel ultrasound probe calibration method for multimodal image guidance of needle placement in cervical cancer brachytherapy

PURPOSE

Interstitial needles placement is a critical component of combined intracavitary/interstitial (IC/IS) brachytherapy (BT). To ensure precise placement of interstitial needles, we proposed a novel ultrasonic (US) probe calibration method to accurately register the US image in the magnetic resonance imaging (MRI) image and provide multimodal image guidance for needle placement.

METHODS

A wire-based calibration phantom combined with the stylus was developed for the calibration of US probe. The calibration phantom helps to quickly align the imaging plane of the US probe with the fiducial points to obtain US images of these points. The coordinates of fiducial points in US images were located automatically by feature extraction algorithms and were further corrected by the proposed correction method. Ingenious structures were designed on both sides of the calibration phantom to accurately obtain the coordinates of the fiducial points relative to the tracking device. Marker validation and pelvic phantom study were performed to evaluate the accuracy of the proposed calibration method.

RESULTS

In the marker validation, the US probe calibration method with corrected transformation achieves a registration accuracy of 0.694 ± 0.014 mm, and the uncorrected one is 0.746 ± 0.018 mm. In the pelvic phantom study, the needle tip difference was 1.096 ± 0.225 mm and trajectory difference was 1.416 ± 0.284 degrees.

CONCLUSION

The proposed US probe calibration method is helpful to achieve more accurate multimodality image guidance for needle placement.

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

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

Deep-learning-assisted algorithm for catheter reconstruction during MR-only gynecological interstitial brachytherapy

Magnetic resonance imaging (MRI) offers excellent soft‐tissue contrast enabling the contouring of targets and organs at risk during gynecological interstitial brachytherapy procedure. Despite its advantage, one of the main obstacles preventing a transition to an MRI‐only workflow is that implanted plastic catheters are not reliably visualized on MR images. This study aims to evaluate the feasibility of a deep‐learning‐based algorithm for semiautomatic reconstruction of interstitial catheters during an MR‐only workflow. MR images of 20 gynecological patients were used in this study. Note that 360 catheters were reconstructed using T1‐ and T2‐weighted images by five experienced brachytherapy planners. The mean of the five reconstructed paths were used for training (257 catheters), validation (15 catheters), and testing/evaluation (88 catheters). To automatically identify and localize the catheters, a two‐dimensional (2D) U‐net algorithm was used to find their approximate location in each image slice. Once localized, thresholding was applied to those regions to find the extrema, as catheters appear as bright and dark regions in T1‐ and T2‐weighted images, respectively. The localized dwell positions of the proposed algorithm were compared to the ground truth reconstruction. Reconstruction time was also evaluated. A total of 34 009 catheter dwell positions were evaluated between the algorithm and all planners to estimate the reconstruction variability. The average variation was 0.97 ± 0.66 mm. The average reconstruction time for this approach was 11 ± 1 min, compared with 46 ± 10 min for the expert planners. This study suggests that the proposed deep learning, MR‐based framework has potential to replace the conventional manual catheter reconstruction. The adoption of this approach in the brachytherapy workflow is expected to improve treatment efficiency while reducing planning time, resources, and human errors.

Inter-fractional variation of markers and applicators in single-implant high-dose-rate interstitial brachytherapy for gynecologic malignancies

PURPOSE

Implanted fiducial markers are a commonly used tool in delineating the CTV in high-dose-rate interstitial brachytherapy (HDR-ISBT) for gynecologic malignancy, but their reliability in gynacological sites is not well understood. These markers and interstitial applicators can experience interfractional motion due to organ swelling or other anatomical changes. The purpose of this study was to evaluate the spatial variation of these features.

METHODS AND MATERIALS

The spatial positions of 50 implanted markers and 202 needles were tracked in 15 patients treated over 70 fractions of HDR brachytherapy. Marker and/or needle coordinates were extracted from CT images with contours and dose distributions. Automated analysis determined marker self-consistency and displacements between various elements of the implant.

RESULTS

From start to end fraction, the relative positions of the markers experienced an average magnitude displacement of 4.5 ± 3.0 mm while the average displacement of the applicator tips was 11 ± 8 mm, relative to their respective centers of mass (CM).

CONCLUSIONS

Markers implanted lateral and superior to the CTV experience greater drift than other implant locations.

High-dose-rate interstitial brachytherapy with hypoxic radiosensitizer KORTUC II for unresectable pelvic sidewall recurrence of uterine cervical cancer: a case report

In order to improve oncologic outcomes in radiotherapy treatments of patients with unresectable pelvic sidewall recurrences of uterine cervical cancer, we combined high-dose-rate interstitial brachytherapy (HDR-ISBT) with newly tested hypoxic radiosensitizer Kochi oxydol-radiation therapy for unresectable carcinomas (KORTUC II), an enzyme-targeting radiosensitization treatment involving intra-tumoral injection of sodium hyaluronate mixed with hydrogen peroxide. We report on a 63-year-old patient referred to our department with an extensive pelvic sidewall recurrence of uterine cervical cancer after initial hysterectomy. The tumor size was 55 × 25 × 80 mm, with a calculated volume of 89.7 cc. Whole pelvic irradiation of 50 Gy in 25 fractions was administered, combined with weekly cisplatin injections. KORTUC II injections were given two times: at day 21 (42 Gy) and at day 24 (48 Gy). After finishing whole pelvic irradiation, HDR-ISBT of 25 Gy in 5 fractions b.i.d. over 3 days was administered. KORTUC II was also injected at the time of implantation. Dose-volume histogram (DVH) values for clinical target volume were D₉₀, D₉₈, and D₁₀₀ of 6.0, 5.0, and 3.5 Gy per fraction, respectively. D_2cc values were 2.1, 4.1, 3.2, and 2.0 Gy per fraction for the bladder, rectum, sigmoid colon, and small bowel, respectively. No acute adverse events ≥ grade 3 were observed. Repeated grade 3 pyelonephritis occurred as a late complication at 11, 24, and 26 months after the treatment, and was successfully resolved with antibiotics. Moreover, grade 2 late toxicity was documented, including sciatic neuralgia, lower limb lymphedema, and urinary incontinence. At present, 32 months after HDR-ISBT, the patient remains free of disease, with no toxicity-related deterioration in physical condition.

Dosimetry of a sonolucent material for an ultrasound-compatible gynecologic high-dose-rate brachytherapy cylinder using Monte Carlo simulation and radiochromic film

PURPOSE

he purpose of this study was to study the dosimetric characterization of sonolucent material "TPX" to be used toward gynecologic high-dose-rate brachytherapy treatments using ultrasound-compatible cylinders in non-model-based dose calculation workflows.

METHODS

Monte Carlo simulations were performed using EGSnrc application egs_brachy in cylinders of polymethylpentene (TPX) plastic, water, and PMMA. Simulations were performed of five 192Ir sources placed longitudinally in ∼3.7 cm diameter, 5.0 cm length cylinders (matching physical cylinders used in film measurements). TPX and PMMA dose distributions and percentage depth dose curves were compared relative to water. Film measurements were performed to validate egs_brachy simulations. TPX and PMMA cylinders were placed in a water tank using 3D-printed supports to position film radially and touching the surface of the cylinders. The same five 192Ir dwell positions were delivered as simulated in egs_brachy.

RESULTS

The egs_brachy and film percentage depth doses agreed within film uncertainties. The egs_brachy relative dose difference between TPX and water was (0.74 ± 0.09)% and between PMMA and water was (-0.79 ± 0.09)% over the dose scoring phantom. Dose differences for TPX and PMMA relative to water were less than ± 1% within 5 cm of the cylinder surface.

CONCLUSIONS

In a solid sonolucent sheath of TPX, the dosimetric differences are comparable with PMMA and other applicator materials in clinical use. No additional uncertainty to dose calculation is introduced when treating through TPX cylinders compared with current applicator materials, and therefore, it is acceptable to perform gynecologic brachytherapy treatments with a sonolucent sheath inserted during radiation delivery.

Imaging Cherenkov emission for quality assurance of high-dose-rate brachytherapy

With advances in high-dose-rate (HDR) brachytherapy, the importance of quality assurance (QA) is increasing to ensure safe delivery of the treatment by measuring dose distribution and positioning the source with much closer intervals for highly active sources. However, conventional QA is time-consuming, involving the use of several different measurement tools. Here, we developed simple QA method for HDR brachytherapy based on the imaging of Cherenkov emission and evaluated its performance. Light emission from pure water irradiated by an ¹⁹²Ir γ-ray source was captured using a charge-coupled device camera. Monte Carlo calculations showed that the observed light was primarily Cherenkov emissions produced by Compton-scattered electrons from the γ-rays. The uncorrected Cherenkov light distribution, which was 5% on average except near the source (within 7 mm from the centre), agreed with the dose distribution calculated using the treatment planning system. The accuracy was attributed to isotropic radiation and short-range Compton electrons. The source positional interval, as measured from the light images, was comparable to the expected intervals, yielding spatial resolution similar to that permitted by conventional film measurements. The method should be highly suitable for quick and easy QA investigations of HDR brachytherapy as it allows simultaneous measurements of dose distribution, source strength, and source position using a single image.

American Brachytherapy Society working group report on the patterns of care and a literature review of reirradiation for gynecologic cancers

PURPOSE

Recurrences of previously irradiated gynecological malignancies are uncommon. Standardized management of these cases is not well established. We aim to provide an in-depth literature review and present current practice patterns among an international group of experienced practitioners in the reirradiation setting of gynecologic cancers.

METHODS AND MATERIALS

An extensive literature search was performed and 35 articles were selected based on preset criteria. A 20-question online survey of 10 experts regarding their retreatment practices was also conducted.

RESULTS

The reviewed publications include a diverse group of patients, multiple treatment techniques, a range of total doses, local control, overall survival, and toxicity outcomes. Overall, local control ranged from 44% to 88% over 1-5 years with OS in the range of 39.5-82% at 2-5 years. Late G3-4 toxicity varied very broadly from 0% to 42.9%, with most papers reporting serious toxicities greater than 15%. The most common reirradiation technique utilized was brachytherapy. Some low-dose-rate data suggest improved outcomes with doses >50 Gy. The high-dose-rate data are more varied with some studies suggesting improved local control with doses >40 Gy. In general, a longer time interval between the first and second course of radiation as well as recurrences <2-4 cm tend to have improved outcomes.

CONCLUSIONS

Reirradiation with brachytherapy results in relatively reasonable local control and toxicities for women with recurrent gynecologic cancers. The appropriate dose for each case needs to be individualized given the heterogeneity of cases. Multidisciplinary management is critical to develop individualized plans and to clearly communicate potential side effects and expected treatment outcomes.

TAKE HOME MESSAGE

Reirradiation with brachytherapy is an acceptable effective organ preserving approach for recurrent gynecologic cancers with a reasonable local control and toxicity profile. Each case requires multidisciplinary management to develop an individualized approach. Monitoring for potential long-term toxicities is essential.

Image-Guided Gynecologic Brachytherapy for Cervical Cancer

The incorporation of magnetic resonance imaging in brachytherapy has resulted in an increased use of interstitial catheters in order to create a comprehensive treatment plan that covers the visualized tumor. However, the insertion with passive, image-guidance requires estimating the location of the tumor during the insertion process, rather than visualizing and inserting the catheters directly to the desired location under active tracking. In order to treat residual disease, multiparametric MR sequences can enhance the information available to the clinician. The precision availed by MR-guided brachytherapy results in substantial improvements in needle positioning, and resulting treatment plans.

Fully automatic catheter segmentation in MRI with 3D convolutional neural networks: application to MRI-guided gynecologic brachytherapy

External-beam radiotherapy followed by high dose rate (HDR) brachytherapy is the standard-of-care for treating gynecologic cancers. The enhanced soft-tissue contrast provided by magnetic resonance imaging (MRI) makes it a valuable imaging modality for diagnosing and treating these cancers. However, in contrast to computed tomography (CT) imaging, the appearance of the brachytherapy catheters, through which radiation sources are inserted to reach the cancerous tissue later on, is often variable across images. This paper reports, for the first time, a new deep-learning-based method for fully automatic segmentation of multiple closely spaced brachytherapy catheters in intraoperative MRI. Represented in the data are 50 gynecologic cancer patients treated by MRI-guided HDR brachytherapy. For each patient, a single intraoperative MRI was used. 826 catheters in the images were manually segmented by an expert radiation physicist who is also a trained radiation oncologist. The number of catheters in a patient ranged between 10 and 35. A deep 3D convolutional neural network (CNN) model was developed and trained. In order to make the learning process more robust, the network was trained 5 times, each time using a different combination of shown patients. Finally, each test case was processed by the five networks and the final segmentation was generated by voting on the obtained five candidate segmentations. 4-fold validation was executed and all the patients were segmented. An average distance error of 2.0  ±  3.4 mm was achieved. False positive and false negative catheters were 6.7% and 1.5% respectively. Average Dice score was equal to 0.60  ±  0.17. The algorithm is available for use in the open source software platform 3D Slicer allowing for wide scale testing and research discussion. In conclusion, to the best of our knowledge, fully automatic segmentation of multiple closely spaced catheters from intraoperative MR images was achieved for the first time in gynecological brachytherapy.

Risk factors for fistula formation after interstitial brachytherapy for locally advanced gynecological cancers involving vagina

Purpose

To determine risk factors for fistula formation after interstitial brachytherapy (ISBT) in patients with advanced gynecologic cancers.

Material and methods

We performed an Institutional Review Board (IRB) approved retrospective review of 44 patients treated with transperineal template-based ISBT from 2011 to 2017 at a major metropolitan county and university health system. All patients were treated with image-guided high-dose-rate ISBT. Statistical analysis was performed using the χ² test to identify factors correlated with fistula formation. Survival and tumor control outcomes were calculated using Kaplan Meier analyses.

Results

Patients had a mean age of 53 years (range, 28-81 years), a mean external beam dose of 43.1 Gy (range, 42.5-51.3 Gy), and a mean brachytherapy dose of 22.8 Gy (range, 21.3-30 Gy). Two of 44 patients had fistulas that could be definitively attributed to therapy for a fistula rate of 4.5%. Six additional patients (13.6%) developed fistula after treatment with associated recurrent disease but were included in the causality analysis. We analyzed patient tumor and treatment factors, and on univariate analyses we found that age ≥ 60 years, Hispanic ethnicity, bladder involvement, rectal D2 cc ≥ 70 Gy, and whether patients had post-radiation biopsies were predictors for fistula formation. The 1-year overall survival (OS), progression-free survival (PFS), and local control (LC) were 85%, 58.5%, and 76.9%, respectively, with a mean follow-up time 23 months (range, 4.0-68.8 months).

Conclusions

We identified factors that predict fistula formation in patients with advanced gynecologic tumors treated with ISBT. These factors can be used to stratify patients into a high-risk group, with potential for modification of brachytherapy planning to reduce their risk of fistula formation.

From Computed Tomography-Guided to Magnetic Resonance Imaging-Guided Intracavitary Brachytherapy for Cervical Cancer: What Do the Key Stakeholders Have to Say about the Transition?

BACKGROUND

International brachytherapy consortiums are advocating for the incorporation of magnetic resonance imaging (MRI) into the cervical brachytherapy process as a standard-of-care. Although some evaluations have been performed to quantify the effect on procedural time, little is known about the views and experiences of key stakeholders during the transition from computed tomography to MR-guided brachytherapy. This qualitative research project explored insights from key stakeholders related to a change in the gynaecologic brachytherapy process.

METHODS AND MATERIALS

Semi-structured interviews were designed using Lean Methodology principles and all key members in the gynaecologic brachytherapy team were approached for participation: radiation oncologists, medical physicists, radiation therapists, the lead MR technologist, and the ward nurse manager. Interviews were recorded and transcribed, and analysis was performed to identify themes from the data.

RESULTS

Ten of 12 (83% participation rate) key members of the team were interviewed. Four themes emerged from the data: challenges to efficiency, staff availability, patient history and disease characteristics, and team communication. The stakeholders expressed that the challenges during this transition were procedural inefficiency (sharing of the MRI scanner and increased procedure length because of increased complexity in contouring and planning), and staff availability (radiation oncologist and transportation staff). The clinical team identified the value of communicating patient history and disease characteristics ahead of the brachytherapy procedure day and also using an inclusive mode of communication during the procedure was beneficial.

CONCLUSIONS

This research provides nuanced insights into process and practice changes that occur when one imaging technology is simply swapped for another, emphasizing how intertwined and complex brachytherapy procedures can be. It emphasizes that not all challenges to efficiency are considered Lean Wastes, and that seemingly simple procedural changes can result in unanticipated differences in staff availability, communication pathways, and knowledge requirements.

An inductively coupled ultra-thin, flexible, and passive RF resonator for MRI marking and guiding purposes: Clinical feasibility

PURPOSE

The purpose of this study is to develop a wireless, flexible, ultra-thin, and passive radiofrequency-based MRI resonant fiducial marker, and to validate its feasibility in a phantom model and several body regions.

METHODS

Standard microfabrication processing was used to fabricate the resonant marker. The proposed marker consists of two metal traces in the shape of a square with an edge length of 8 mm, with upper and lower traces connected to each other by a metalized via. A 3T MRI fiducial marking procedure was tested in phantom and ex vivo, and then the marker's performance was evaluated in an MRI experiment using humans. The radiofrequency safety was also tested using temperature sensors in the proximity of the resonator.

RESULTS

A flexible resonator with a thickness of 115 μm and a dimension of 8 × 8 mm was obtained. The experimental results in the phantom show that at low background flip angles (6-18°), the resonant marker enables precise and rapid visibility, with high marker-to-background contrast and signal-to-noise ratio improvement of greater than 10 in the vicinity of the marker. Temperature analysis showed a specific absorption ratio gain of 1.3. Clinical studies further showed a successful biopsy procedure using the fiducial marking functionality of our device.

CONCLUSIONS

The ultra-thin and flexible structure of this wireless flexible radiofrequency resonant marker offers effective and safe MR visualization with high feasibility for anatomic marking and guiding at various regions of the body. Magn Reson Med 80:361-370, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Prospective Clinical Implementation of a Novel Magnetic Resonance Tracking Device for Real-Time Brachytherapy Catheter Positioning

PURPOSE

We designed and built dedicated active magnetic resonance (MR)-tracked (MRTR) stylets. We explored the role of MRTR in a prospective clinical trial.

METHODS AND MATERIALS

Eleven gynecologic cancer patients underwent MRTR to rapidly optimize interstitial catheter placement. MRTR catheter tip location and orientation were computed and overlaid on images displayed on in-room monitors at rates of 6 to 16 frames per second. Three modes of actively tracked navigation were analyzed: coarse navigation to the approximate region around the tumor; fine-tuning, bringing the stylets to the desired location; and pullback, with MRTR stylets rapidly withdrawn from within the catheters, providing catheter trajectories for radiation treatment planning (RTP). Catheters with conventional stylets were inserted, forming baseline locations. MRTR stylets were substituted, and catheter navigation was performed by a clinician working inside the MRI bore, using monitor feedback.

RESULTS

Coarse navigation allowed repositioning of the MRTR catheters tips by 16 mm (mean), relative to baseline, in 14 ± 5 s/catheter (mean ± standard deviation [SD]). The fine-tuning mode repositioned the catheter tips by a further 12 mm, in 24 ± 17 s/catheter. Pullback mode provided catheter trajectories with RTP point resolution of ∼1.5 mm, in 1 to 9 s/catheter.

CONCLUSIONS

MRTR-based navigation resulted in rapid and optimal placement of interstitial brachytherapy catheters. Catheters were repositioned compared with the initial insertion without tracking. In pullback mode, catheter trajectories matched computed tomographic precision, enabling their use for RTP.

Pre-plan technique feasibility in multi-interstitial/endocavitary perineal gynecological brachytherapy

Purpose

To present the implementation of a magnetic resonance imaging (MRI) pre-planning technique in multi-interstitial perineal and endocavitary gynecological brachytherapy.

Material and methods

We used a new fully MRI-compatible applicator that is capable to engage titanium needles, and an intrauterine tandem, developed in our department for the treatment of gynecological cervical cancer patients. This applicator is an attempt to combine the technical advantages of the Martinez universal perineal interstitial template (MUPIT) with the improvement in dose distribution by adding an intrauterine probe with the imaging advantages of MRI-based brachytherapy, thus preserving the stability, geometry, and robustness of the implant, avoiding possible errors of free-hand needle placement. A pre-brachytherapy MRI T2 acquisition is carried out with the template in place 3-5 days before the implant. On this image set, clinical target volume (CTV) is drawn. The required needles and their depths are selected accordingly to encompass the CTV (as conformal as possible). To facilitate this task, a Java based application linked to the treatment planning system has been developed. From this procedure, each needle identification and its depth are obtained previously to the implantation. With this information, the radiation oncologist proceeds with implant and then, a post-implant MRI is carried out, in which the contouring, needles, tandem reconstruction, and optimization are established.

Results

This pre-planning procedure has been successfully applied in 10 patients. An excellent reproduction of the virtual pre-planning has been achieved.

Conclusions

We describe a virtual pre-planning technique using a multi-interstitial and endocavitary perineal template. It is based on a virtual work with MRI images. This procedure has shown to be feasible and efficient in clinical practice by facilitating the work of specialists, and reducing uncertainties of the application.

MR- versus CT-based high-dose-rate interstitial brachytherapy for vaginal recurrence of endometrial cancer

PURPOSE

To compare clinical outcomes of MR-based versus CT-based high-dose-rate interstitial brachytherapy (ISBT) for vaginal recurrence of endometrioid endometrial cancer (EC).

METHODS AND MATERIALS

We reviewed 66 patients with vaginal recurrent EC; 18 had MR-based ISBT on a prospective clinical trial and 48 had CT-based treatment. Kaplan-Meier survival modeling was used to generate estimates for local control (LC), disease-free interval (DFI), and overall survival (OS), and multivariate Cox modeling was used to assess prognostic factors. Toxicities were evaluated and compared.

RESULTS

Median followup was 33 months (CT 30 months, MR 35 months). Median cumulative equivalent dose in 2-Gy fractions was 75.5 Gy for MR-ISBT and 73.8 Gy for CT-ISBT (p = 0.58). MR patients were older (p = 0.03) and had larger tumor size (>4 cm vs. ≤ 4 cm) compared to CT patients (p = 0.04). For MR-based versus CT-based ISBT, 3-year KM rate for local control was 100% versus 78% (p = 0.04), DFI was 69% versus 55% (p = 0.1), and OS was 63% versus 75% (p = 0.81), respectively. On multivariate analysis, tumor Grade 3 was associated with worse OS (HR 3.57, 95% CI 1.25, 11.36) in a model with MR-ISBT (HR 0.56, 95% CI 0.16, 1.89). Toxicities were not significantly different between the two modalities.

CONCLUSION

Despite worse patient prognostic features, MR-ISBT was associated with a significantly better (100%) 3-year local control, comparable survival, and improved DFI rates compared to CT. Toxicities did not differ compared to CT-ISBT patients. Tumor grade contributed as the most significant predictor for survival. Larger prospective studies are needed to assess the impact of MR-ISBT on survival outcomes.

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

PURPOSE

In 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 MATERIALS

We 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.

RESULTS

Mean 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 D_0.1cc and D_0.5cc, as well as EQD2 D_0.1cc and EQD2 D_0.5cc when applied to a full course of treatment (45 Gy EBRT + 25 Gy IBBT).

CONCLUSIONS

We 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.

Toward a 3D transrectal ultrasound system for verification of needle placement during high-dose-rate interstitial gynecologic brachytherapy

PURPOSE

Treatment for gynecologic cancers, such as cervical, recurrent endometrial, and vaginal malignancies, commonly includes external-beam radiation and brachytherapy. In high-dose-rate (HDR) interstitial gynecologic brachytherapy, radiation treatment is delivered via hollow needles that are typically inserted through a template on the perineum with a cylinder placed in the vagina for stability. Despite the need for precise needle placement to minimize complications and provide optimal treatment, there is no standard intra-operative image-guidance for this procedure. While some image-guidance techniques have been proposed, including magnetic resonance (MR) imaging, X-ray computed tomography (CT), and two-dimensional (2D) transrectal ultrasound (TRUS), these techniques have not been widely adopted. In order to provide intra-operative needle visualization and localization during interstitial brachytherapy, we have developed a three-dimensional (3D) TRUS system. This study describes the 3D TRUS system and reports on the system validation and results from a proof-of-concept patient study.

METHODS

To obtain a 3D TRUS image, the system rotates a conventional 2D endocavity transducer through 170 degrees in 12 s, reconstructing the 2D frames into a 3D image in real-time. The geometry of the reconstruction was validated using two geometric phantoms to ensure the accuracy of the linear measurements in each of the image coordinate directions and the volumetric accuracy of the system. An agar phantom including vaginal and rectal canals, as well as a model uterus and tumor, was designed and used to test the visualization and localization of the interstitial needles under idealized conditions by comparing the needles' positions between the 3D TRUS scan and a registered MR image. Five patients undergoing HDR interstitial gynecologic brachytherapy were imaged using the 3D TRUS system following the insertion of all needles. This image was manually, rigidly registered to the clinical postinsertion CT scan based on the vaginal cylinder of the needle template. The positions of the tips and the trajectory of the needle paths were compared between the modalities.

RESULTS

The observed geometric errors of the system were ≤ 0.3 mm in each of the three coordinate planes of the 3D US image and the mean measured volumetric error was 0.10 cm³ . In the phantom study, the mean needle tip difference was 1.54 ± 0.71 mm and the mean trajectory difference was 0.94 ± 0.89 degrees (n = 14). In the in vivo study, a total of 73 needles were placed, of which 88% of needles were visible and 79% of tips were identifiable in the 3D TRUS images. Six of the nine needles that were not visible were due to shadowing artifacts created by the presence of the vaginal cylinder of the needle template. The mean distance between corresponding needle tips in the two modalities was 3.82 ± 1.86 mm and the mean trajectory difference was 3.04 ± 1.63 degrees for the five patients.

CONCLUSIONS

In this proof-of-concept study, the 3D TRUS system allowed for localization of needles not obscured by shadowing artifacts, providing a method for visualizing needles intra-operatively during HDR interstitial brachytherapy of gynecologic cancers and providing the potential for 3D image-guidance.

Comparison of outcomes for MR-guided versus CT-guided high-dose-rate interstitial brachytherapy in women with locally advanced carcinoma of the cervix

OBJECTIVE

The purpose was to compare local control (LC), overall survival (OS) and dose to the organs at risk (OAR) in women with locally advanced cervical cancer treated with MR-guided versus CT-guided interstitial brachytherapy (BT).

METHODS

56 patients (29 MR, 27 CT) were treated with high-dose-rate (HDR) interstitial BT between 2005-2015. The MR patients had been prospectively enrolled on a Phase II clinical trial. Data were analyzed using Kaplan-Meier (K-M) and Cox proportional hazards statistical modeling in JMP® & R®.

RESULTS

Median follow-up time was 19.7months (MR group) and 18.4months (CT group). There were no statistically significant differences in patient age at diagnosis, histology, percent with tumor size >4cm, grade, FIGO stage or lymph node involvement between the groups. Patients in the MR group had more lymphovascular involvement compared to patients in the CT group (p<0.01). When evaluating plans generated, there were no statistically significant differences in median cumulative dose to the high-risk clinical target volume or the OAR. 2-year K-M LC rates for MR-based and CT-based treatments were 96% and 87%, respectively (log-rank p=0.65). At 2years, OS was significantly better in the MR-guided cohort (84% vs. 56%, p=0.036). On multivariate analysis, squamous histology was associated with longer OS (HR 0.23, 95% CI 0.07-0.72) in a model with MR BT (HR 0.35, 95% CI 0.08-1.18). There was no difference in toxicities between CT and MR BT.

CONCLUSION

In this population of locally advanced cervical-cancer patients, MR-guided HDR BT resulted in estimated 96% 2-year local control and excellent survival and toxicity rates.

Outcomes with volume-based dose specification in CT-planned high-dose-rate brachytherapy for stage I-II cervical carcinoma: A 10-year institutional experience

OBJECTIVE

To determine prognostic factors for progression-free survival (PFS) and overall survival (OS) for stage I-II cervical-cancer patients treated using computed-tomography (CT)-planned high-dose-rate (HDR) intracavitary brachytherapy (BT).

METHODS

A total of 150 patients were treated for Stage I-II cervical cancer using CT-planned BT between 4/2004 and 10/2014. Of these, 128 were eligible for inclusion. Kaplan-Meier local control (LC), pelvic control (PC), overall survival (OS), and PFS estimates were calculated.

RESULTS

After a median follow-up of 30months, the 2-year LC rate was 96%, PFS was 88%, and OS was 88%. Overall, 18 patients (14%) experienced any recurrence (AR), 8 had distant recurrence only and 10 had a combination of local, pelvic, regional, and distant recurrence. No patients had LR only. A prognostic factor for AR was tumor size >4cm (p=0.01). Patients with tumors >4cm were 3.3 times more likely to have AR than those with tumors ≤4cm (hazard ratio [HR]=3.3; 95% confidence interval [CI] 1.28-9.47). Point A was 85% of prescription for tumors < 4 cm and decreased approximately 3% over 5 fractions compared to 90% of prescription for tumors > 4 cm that decreased approximately 4% over 5 fractions. Two patients (2%) experienced grade≥2 late toxicity. There were no acute or late grade≥3 toxicities.

CONCLUSION

CT-planned BT resulted in excellent local control and survival. Large tumor size was associated with an increased risk of recurrence outside the radiation field and worse PFS and OS. A volume-optimized plan treated a smaller area than a point A standard plan for patients with Stage I-II cervical cancer that have received chemoradiation. Given the outstanding LC achieved with modern therapy including chemoradiation, HDR, and image-based BT, further efforts to combat spread outside the radiation field with novel therapies are warranted.

Evaluation of an active magnetic resonance tracking system for interstitial brachytherapy

PURPOSE

In gynecologic cancers, magnetic resonance (MR) imaging is the modality of choice for visualizing tumors and their surroundings because of superior soft-tissue contrast. Real-time MR guidance of catheter placement in interstitial brachytherapy facilitates target coverage, and would be further improved by providing intraprocedural estimates of dosimetric coverage. A major obstacle to intraprocedural dosimetry is the time needed for catheter trajectory reconstruction. Herein the authors evaluate an active MR tracking (MRTR) system which provides rapid catheter tip localization and trajectory reconstruction. The authors assess the reliability and spatial accuracy of the MRTR system in comparison to standard catheter digitization using magnetic resonance imaging (MRI) and CT.

METHODS

The MRTR system includes a stylet with microcoils mounted on its shaft, which can be inserted into brachytherapy catheters and tracked by a dedicated MRTR sequence. Catheter tip localization errors of the MRTR system and their dependence on catheter locations and orientation inside the MR scanner were quantified with a water phantom. The distances between the tracked tip positions of the MRTR stylet and the predefined ground-truth tip positions were calculated for measurements performed at seven locations and with nine orientations. To evaluate catheter trajectory reconstruction, fifteen brachytherapy catheters were placed into a gel phantom with an embedded catheter fixation framework, with parallel or crossed paths. The MRTR stylet was then inserted sequentially into each catheter. During the removal of the MRTR stylet from within each catheter, a MRTR measurement was performed at 40 Hz to acquire the instantaneous stylet tip position, resulting in a series of three-dimensional (3D) positions along the catheter's trajectory. A 3D polynomial curve was fit to the tracked positions for each catheter, and equally spaced dwell points were then generated along the curve. High-resolution 3D MRI of the phantom was performed followed by catheter digitization based on the catheter's imaging artifacts. The catheter trajectory error was characterized in terms of the mean distance between corresponding dwell points in MRTR-generated catheter trajectory and MRI-based catheter digitization. The MRTR-based catheter trajectory reconstruction process was also performed on three gynecologic cancer patients, and then compared with catheter digitization based on MRI and CT.

RESULTS

The catheter tip localization error increased as the MRTR stylet moved further off-center and as the stylet's orientation deviated from the main magnetic field direction. Fifteen catheters' trajectories were reconstructed by MRTR. Compared with MRI-based digitization, the mean 3D error of MRTR-generated trajectories was 1.5 ± 0.5 mm with an in-plane error of 0.7 ± 0.2 mm and a tip error of 1.7 ± 0.5 mm. MRTR resolved ambiguity in catheter assignment due to crossed catheter paths, which is a common problem in image-based catheter digitization. In the patient studies, the MRTR-generated catheter trajectory was consistent with digitization based on both MRI and CT.

CONCLUSIONS

The MRTR system provides accurate catheter tip localization and trajectory reconstruction in the MR environment. Relative to the image-based methods, it improves the speed, safety, and reliability of the catheter trajectory reconstruction in interstitial brachytherapy. MRTR may enable in-procedural dosimetric evaluation of implant target coverage.

Outcomes with image-based interstitial brachytherapy for vaginal cancer

PURPOSE

To compare clinical outcomes of image-based versus non-image-based interstitial brachytherapy (IBBT) for vaginal cancer.

METHODS AND MATERIALS

Of 72 patients with vaginal cancer treated with brachytherapy (BT), 47 had image guidance (CT=31, MRI=16) and 25 did not. Kaplan-Meier (KM) estimates were generated for any recurrence, local control (LC), disease-free interval (DFI), and overall survival (OS) and Cox models were used to assess prognostic factors.

RESULTS

Median age was 66 and median follow-up time was 24months. Median cumulative EQD2 dose was 80.8Gy in the non-IBBT group and 77Gy in the IBBT group. For non-IBBT versus IBBT, the 2-year KM LC was 71% vs. 93% (p=0.03); DFI was 54% vs. 86% (p=0.04); and OS 52% vs. 82% (p=0.35). On multivariate analysis, IBBT was associated with better DFI (HR 0.24, 95% CI 0.07-0.73). Having any 2 or more of chemotherapy, high-dose-rate (HDR) BT or IBBT (temporally correlated variables) significantly reduced risk of relapse (HR=0.33, 95% CI=0.13-0.83), compared to having none of these factors.

CONCLUSION

Over time, the use of chemotherapy, HDR, and IBBT has increased in vaginal cancer. The combination of these factors resulted in the highest rates of disease control. Image-guided brachytherapy for vaginal cancer patients maximizes disease control.

Comparison of manual and inverse optimisation techniques in high dose rate intracavitary brachytherapy of cervical cancer: A dosimetric study

AIMS AND OBJECTIVES

To compare dosimetrically the manual optimisation with IPSA using dose volume histograms (DVH) among patients treated for carcinoma of cervix with intracavitary brachytherapy.

BACKGROUND

With the advent of advanced imaging modalities, there has been a shift from conventional X-ray based planning to three-dimensional planning. Manual optimisation is widely used across various institutions but it is time consuming and operator dependant. Inverse planning simulated annealing (IPSA) is now available in various brachytherapy planning systems. But there is a paucity of studies comparing manual optimisation and IPSA in treatment of carcinoma cervix with intracavitary brachytherapy and hence this study.

MATERIALS AND METHODS

Fifteen consecutive patients treated between December 2013 and March 2014 with intracavitary brachytherapy for carcinoma of cervix were selected for this study. All patients were initially treated with external beam radiotherapy followed by intracavitary brachytherapy. The DVH was evaluated and compared between manually optimised plans and IPSA in the same set of patients.

RESULTS

There was a significant improvement in the HRCTV coverage, mean V100 of 87.75% and 82.37% (p = 0.001) and conformity index 0.67 and 0.6 (p = 0.007) for plans generated using IPSA and manual optimisation, respectively. Homogeneity index and dose to the OARs remained similar between the two groups.

CONCLUSION

The use of inverse planning in intracavitary brachytherapy of cervix has shown a significant improvement in the target volume coverage when compared with manual planning.

Treatment results of image-guided high-dose-rate interstitial brachytherapy for pelvic recurrence of uterine cancer

PURPOSE

We analyzed clinical data to evaluate the effectiveness of image-guided high-dose-rate interstitial brachytherapy (HDR-ISBT) for pelvic recurrence of uterine cancer.

METHODS AND MATERIALS

Between 2003 and 2011, 56 patients were treated with HDR-ISBT with or without external beam radiotherapy (EBRT). The median followup time was 33 months (range, 1-109 months). Pre-ISBT treatments included radical hysterectomy for 35 patients (Group A), radical hysterectomy with postoperative radiotherapy for 8 patients (Group B), and radical radiotherapy for 13 patients (Group C). We initiated MRI-assisted CT-based planning for the last 49 patients. The median ISBT single fraction dose was 6 Gy. The median total doses were 30 and 54 Gy with and without EBRT (range, 30-50 Gy) for Group A, respectively and 48 Gy without EBRT for Groups B and C.

RESULTS

The 3-year local control (LC) rates were 85%, 75%, and 46% for Groups A, B, and C, respectively (p = 0.017). The 3-year LC rates were 84%, 73%, and 33% for clinical target volume at the time of HDR-ISBT of <10, 10-29, and ≥30 cc, respectively (p = 0.005). The 3-year LC results tended to be higher for patients whose D100 (clinical target volume) was equal or higher than 67.1 Gy (p = 0.098). A total of 13 late complications of Grades 3-5 occurred in 11 patients (20%).

CONCLUSIONS

Our image-guided HDR-ISBT for pelvic recurrence of uterine cancer provided good treatment outcomes. The treatment results for patients who underwent radical surgery with or without postoperative radiotherapy are better than those for patients who underwent radical radiotherapy.

MRI-assisted cervix cancer brachytherapy pre-planning, based on application in paracervical anaesthesia: final report

Background

Optimal applicator insertion is a precondition for the success of cervix cancer brachytherapy (BT). We aimed to assess feasibility and efficacy of MRI-assisted pre-planning, based on applicator insertion in para-cervical anaesthesia (PCA).

Patients and methods.

Five days prior to BT, the pre-planning procedure was performed in 18 cervix cancer patients: tandem-ring applicator was inserted under PCA, pelvic MRI obtained and applicator removed. Procedure tolerability was assessed. High risk clinical target volume (HR CTV) and organs at risk were delineated on the pre-planning MRI, virtual needles placed at optimal positions, and dose planning performed. At BT, insertion was carried out in subarachnoidal anaesthesia according to pre-planned geometry. Pre-planned and actual treatment parameters were compared.

Results

Pre-planning procedure was well tolerated. Median difference between the pre-planned and actual needle insertion depth and position were 2 (0–10) mm and 4 (0–30) degrees, respectively. The differences between the pre-planned and actual geometric and dosimetric parameters were statistically non-significant. All actual needles were positioned inside the HR CTV and outside the organs at risk (OAR).

Conclusions

Our pre-planning approach is well tolerated and effective. Pre-planned geometry and dose distribution can be reproduced at BT.

Dose error from deviation of dwell time and source position for high dose-rate 192Ir in remote afterloading system

The influence of deviations in dwell times and source positions for (192)Ir HDR-RALS was investigated. The potential dose errors for various kinds of brachytherapy procedures were evaluated. The deviations of dwell time ΔT of a (192)Ir HDR source for the various dwell times were measured with a well-type ionization chamber. The deviations of source position ΔP were measured with two methods. One is to measure actual source position using a check ruler device. The other is to analyze peak distances from radiographic film irradiated with 20 mm gap between the dwell positions. The composite dose errors were calculated using Gaussian distribution with ΔT and ΔP as 1σ of the measurements. Dose errors depend on dwell time and distance from the point of interest to the dwell position. To evaluate the dose error in clinical practice, dwell times and point of interest distances were obtained from actual treatment plans involving cylinder, tandem-ovoid, tandem-ovoid with interstitial needles, multiple interstitial needles, and surface-mold applicators. The ΔT and ΔP were 32 ms (maximum for various dwell times) and 0.12 mm (ruler), 0.11 mm (radiographic film). The multiple interstitial needles represent the highest dose error of 2%, while the others represent less than approximately 1%. Potential dose error due to dwell time and source position deviation can depend on kinds of brachytherapy techniques. In all cases, the multiple interstitial needles is most susceptible.

Real-time active MR-tracking of metallic stylets in MR-guided radiation therapy

PURPOSE

To develop an active MR-tracking system to guide placement of metallic devices for radiation therapy.

METHODS

An actively tracked metallic stylet for brachytherapy was constructed by adding printed-circuit micro-coils to a commercial stylet. The coil design was optimized by electromagnetic simulation, and has a radio-frequency lobe pattern extending ∼5 mm beyond the strong B0 inhomogeneity region near the metal surface. An MR-tracking sequence with phase-field dithering was used to overcome residual effects of B0 and B1 inhomogeneities caused by the metal, as well as from inductive coupling to surrounding metallic stylets. The tracking system was integrated with a graphical workstation for real-time visualization. The 3 Tesla MRI catheter-insertion procedures were tested in phantoms and ex vivo animal tissue, and then performed in three patients during interstitial brachytherapy.

RESULTS

The tracking system provided high-resolution (0.6 × 0.6 × 0.6 mm(3) ) and rapid (16 to 40 frames per second, with three to one phase-field dithering directions) catheter localization in phantoms, animals, and three gynecologic cancer patients.

CONCLUSION

This is the first demonstration of active tracking of the shaft of metallic stylet in MR-guided brachytherapy. It holds the promise of assisting physicians to achieve better targeting and improving outcomes in interstitial brachytherapy.

Dosimetric consequences of interobserver variability in delineating the organs at risk in gynecologic interstitial brachytherapy

PURPOSE

To investigate the dosimetric variability associated with interobserver organ-at-risk delineation differences on computed tomography in patients undergoing gynecologic interstitial brachytherapy.

METHODS AND MATERIALS

The rectum, bladder, and sigmoid of 14 patients treated with gynecologic interstitial brachytherapy were retrospectively contoured by 13 physicians. Geometric variability was calculated using κ statistics, conformity index (CIgen), and coefficient of variation (CV) of volumes contoured across physicians. Dosimetric variability of the single-fraction D0.1cc and D2cc was assessed through CV across physicians, and the standard deviation of the total EQD2 (equivalent dose in 2 Gy per fraction) brachytherapy dose (SD(TOT)) was calculated.

RESULTS

The population mean ± 1 standard deviation of κ, CIgen, and volume CV were, respectively: 0.77 ± 0.06, 0.70 ± 0.08, and 20% ± 6% for bladder; 0.74 ± 06, 0.67 ± 0.08, and 20% ± 5% for rectum; and 0.33 ± 0.20, 0.26 ± 0.17, and 82% ± 42% for sigmoid. Dosimetric variability was as follows: for bladder, CV = 31% ± 19% (SD(TOT) = 72 ± 64 Gy) for D0.1cc and CV = 16% ± 10% (SD(TOT) = 9 ± 6 Gy) for D2cc; for rectum, CV = 11% ± 5% (SD(TOT) = 16 ± 17 Gy) for D0.1cc and CV = 7% ± 2% (SD(TOT) = 4 ± 3 Gy) for D2cc; for sigmoid, CV = 39% ± 28% (SD(TOT) = 12 ± 18 Gy) for D0.1cc and CV = 34% ± 19% (SD(TOT) = 4 ± 4 Gy) for D2cc.

CONCLUSIONS

Delineation of bladder and rectum by 13 physicians demonstrated substantial geometric agreement and resulted in good dosimetric agreement for all dose-volume histogram parameters except bladder D0.1cc. Small delineation differences in high-dose regions by the posterior bladder wall may explain these results. The delineation of sigmoid showed fair geometric agreement. The higher dosimetric variability for sigmoid compared with rectum and bladder did not correlate with higher variability in the total brachytherapy dose but rather may be due to the sigmoid being positioned in low-dose regions in the cases analyzed in this study.

Validation of mathematical models for the prediction of organs-at-risk dosimetric metrics in high-dose-rate gynecologic interstitial brachytherapy

PURPOSE

Given the complicated nature of an interstitial gynecologic brachytherapy treatment plan, the use of a quantitative tool to evaluate the quality of the achieved metrics compared to clinical practice would be advantageous. For this purpose, predictive mathematical models to predict the D2cc of rectum and bladder in interstitial gynecologic brachytherapy are discussed and validated.

METHODS

Previous plans were used to establish the relationship between D2cc and the overlapping volume of the organ at risk with the targeted area (C0) or a 1-cm expansion of the target area (C1). Three mathematical models were evaluated: D2cc = α*C1 + β (LIN); D2cc = α - exp(-β*C0) (EXP); and a mixed approach (MIX), where both C0 and C1 were inputs of the model. The parameters of the models were optimized on a training set of patient data, and the predictive error of each model (predicted D2cc - real D2cc) was calculated on a validation set of patient data. The data of 20 patients were used to perform a K-fold cross validation analysis, with K = 2, 4, 6, 8, 10, and 20.

RESULTS

MIX was associated with the smallest mean prediction error <6.4% for an 18-patient training set; LIN had an error <8.5%; EXP had an error <8.3%. Best case scenario analysis shows that an error ≤ 5% can be achieved for a ten-patient training set with MIX, an error ≤ 7.4% for LIN, and an error ≤ 6.9% for EXP. The error decreases with the increase in training set size, with the most marked decrease observed for MIX.

CONCLUSIONS

The MIX model can predict the D2cc of the organs at risk with an error lower than 5% with a training set of ten patients or greater. The model can be used in the development of quality assurance tools to identify treatment plans with suboptimal sparing of the organs at risk. It can also be used to improve preplanning and in the development of real-time intraoperative planning tools.

Development of an open source software module for enhanced visualization during MR-guided interstitial gynecologic brachytherapy

In 2010, gynecologic malignancies were the 4th leading cause of death in U.S. women and for patients with extensive primary or recurrent disease, treatment with interstitial brachytherapy may be an option.

However, brachytherapy requires precise insertion of hollow catheters with introducers into the tumor in order to eradicate the cancer. In this study, a software solution to assist interstitial gynecologic brachytherapy has been investigated and the software has been realized as an own module under (3D) Slicer, which is a free open source software platform for (translational) biomedical research. The developed research module allows on-time processing of intra-operative magnetic resonance imaging (iMRI) data over a direct DICOM connection to a MR scanner. Afterwards follows a multi-stage registration of CAD models of the medical brachytherapy devices (template, obturator) to the patient’s MR images, enabling the virtual placement of interstitial needles to assist the physician during the intervention.

Dosimetric comparison of optimization methods for multichannel intracavitary brachytherapy for superficial vaginal tumors

PURPOSE

Multichannel vaginal applicators allow treatment of a more conformal volume compared with a single, central vaginal channel. There are several optimization methods available for use with multichannel applicators, but no previous comparison of these has been performed in the treatment of superficial vaginal tumors. Accordingly, a feasibility study was completed to compare inverse planning by simulated annealing (IPSA), dose point optimization (DPO), and graphical optimization for high-dose-rate brachytherapy using a multichannel, intracavitary vaginal cylinder.

METHODS AND MATERIALS

This comparative study used CT data sets from five patients with superficial vaginal recurrences of endometrial cancer treated with multichannel intracavitary high-dose-rate brachytherapy. Treatment plans were generated using DPO, graphical optimization, surface optimization with IPSA (surf IPSA), and two plans using volume optimization with IPSA. The plans were evaluated for target coverage, conformal index, dose homogeneity index, and dose to organs at risk.

RESULTS

Best target coverage was achieved by volume optimization with IPSA 2 and surf IPSA with mean V100 values of 93.89% and 91.87%, respectively. Doses for the most exposed 2-cm(3) of the bladder (bladder D2cc) was within tolerance for all optimization methods. Rectal D2cc was above tolerance for one DPO plan. All volume optimization with IPSA plans resulted in higher vaginal mucosa doses for all patients. Greatest homogeneity within the target volume was seen with surf IPSA and DPO. Highest conformal indices were seen with surf IPSA and graphical optimization.

CONCLUSIONS

Optimization with surf IPSA was user friendly for the generation of treatment plans and achieved good target coverage, conformity, and homogeneity with acceptable doses to organs at risk.

Concurrent chemoradiation for vaginal cancer

Background

It is not known whether the addition of chemotherapy to radiation therapy improves outcomes in primary vaginal cancer. Here, we review clinical outcomes in patients with primary vaginal cancer treated with radiation therapy (RT) or concurrent chemoradiation therapy (CRT).

Methods

Seventy-one patients with primary vaginal cancer treated with definitive RT with or without concurrent chemotherapy at a single institution were identified and their records reviewed. A total of 51 patients were treated with RT alone; 20 patients were treated with CRT. Recurrences were analyzed. Overall survival (OS) and disease-free survival (DFS) rates were estimated using the Kaplan-Meier method. Cox regression analysis was performed.

Results

The median age at diagnosis was 61 years (range, 18–92 years) and the median follow-up time among survivors was 3.0 years. Kaplan-Meier estimates for OS and DFS differed significantly between the RT and CRT groups (3-yr OS = 56% vs. 79%, log-rank p = 0.037; 3-yr DFS = 43% vs. 73%, log-rank p = 0.011). Twenty-three patients (45%) in the RT group had a relapse at any site compared to 3 (15%) in the CRT group (p = 0.027). With regard to the sites of first relapse, 10 patients (14%) had local only, 4 (6%) had local and regional, 9 (13%) had regional only, 1 (1%) had regional and distant, and 2 (3%) had distant only relapse. On univariate analysis, the use of concurrent chemotherapy, FIGO stage, tumor size, and date of diagnosis were significant predictors of DFS. On multivariate analysis, the use of concurrent chemotherapy remained a significant predictor of DFS (hazard ratio 0.31 (95% CI, 0.10–0.97; p = 0.04)).

Conclusions

Vaginal cancer results in poor outcomes. Adequate radiation dose is essential to ensure curative management. Concurrent chemotherapy should be considered for vaginal cancer patients.

3-T MR-guided brachytherapy for gynecologic malignancies

Gynecologic malignancies are a leading cause of death in women worldwide. Standard treatment for many primary and recurrent gynecologic cancer cases includes external-beam radiation followed by brachytherapy. Magnetic resonance (MR) imaging is beneficial in diagnostic evaluation, in mapping the tumor location to tailor radiation dose and in monitoring the tumor response to treatment. Initial studies of MR guidance in gynecologic brachytherapy demonstrate the ability to optimize tumor coverage and reduce radiation dose to normal tissues, resulting in improved outcomes for patients. In this article, we describe a methodology to aid applicator placement and treatment planning for 3 Tesla (3-T) MR-guided brachytherapy that was developed specifically for gynecologic cancers. This methodology has been used in 18 cases from September 2011 to May 2012 in the Advanced Multimodality Image Guided Operating (AMIGO) suite at Brigham and Women's Hospital. AMIGO comprises state-of-the-art tools for MR imaging, image analysis and treatment planning. An MR sequence using three-dimensional (3D)-balanced steady-state free precession in a 3-T MR scanner was identified as the best sequence for catheter identification with ballooning artifact at the tip. 3D treatment planning was performed using MR images. Items in development include software designed to support virtual needle trajectory planning that uses probabilistic bias correction, graph-based segmentation and image registration algorithms. The results demonstrate that 3-T MR image guidance has a role in gynecologic brachytherapy. These novel developments have the potential to improve targeted treatment to the tumor while sparing the normal tissues.

American Brachytherapy Society consensus guidelines for locally advanced carcinoma of the cervix. Part I: general principles

PURPOSE

To develop brachytherapy recommendations covering aspects of pretreatment evaluation, treatment, and dosimetric issues for locally advanced cervical cancer.

METHODS

Members of the American Brachytherapy Society (ABS) with expertise in cervical cancer brachytherapy formulated updated recommendations for locally advanced (Federation of Gynecology and Obstetrics Stages IB2-IVA) cervical cancer based on literature review and clinical experience.

RESULTS

The ABS recommends the use of brachytherapy as a component of the definitive treatment of locally advanced cervical carcinoma. Precise applicator placement is necessary to maximize the probability of achieving local control without major side effects. The ABS recommends a cumulative delivered dose of approximately 80-90Gy for definitive treatment. The dose delivered to point A should be reported for all brachytherapy applications regardless of treatment-planning technique. The ABS also recommends adoption of the Groupe Européen Curiethérapie-European Society of Therapeutic Radiation Oncology (GEC-ESTRO) guidelines for contouring, image-based treatment planning, and dose reporting. Interstitial brachytherapy may be considered for a small proportion of patients whose disease cannot be adequately encompassed by intracavitary application. It should be performed by practitioners with special expertise in these procedures.

CONCLUSIONS

Updated ABS recommendations are provided for brachytherapy for locally advanced cervical cancer. Practitioners and cooperative groups are encouraged to use these recommendations to formulate their clinical practices and to adopt dose-reporting policies that are critical for outcome analysis.

Dose-volume parameters and clinical outcome of CT-guided free-hand high-dose-rate interstitial brachytherapy for cervical cancer

Currently, image-based 3-dimentional (3D) planning brachytherapy allows for a better assessment of gross tumor volume (GTV) and the definition and delineation of target volume in cervix cancer. In this study, we investigated the feasibility of our novel computed tomography (CT)-guided free-hand high-dose-rate interstitial brachytherapy (HDRISBT) technique for cervical cancer by evaluating the dosimetry and preliminary clinical outcome of this approach. Dose-volume histogram (DVH) parameters were analyzed according to the Gynecological GEC-ESTRO Working Group recommendations for image-based 3D treatment in cervical cancer. Twenty cervical cancer patients who underwent CT-guided free-hand HDRISBT between March 2009 and June 2010 were studied. With a median of 5 (range, 4-7) implanted needles for each patient, the median dose of brachytherapy alone delivered to 90% of the target volume (D90) was 45 (range, 33-54) Gyα/β10 for high-risk clinical target volume (HR-CTV) and 30 (range, 20-36) Gyα/β10 for intermediate-risk clinical target volume (IR-CTV). The percentage of the CTV covered by the prescribed dose (V100) of HR-CTV with brachytherapy alone was 81.9%-99.2% (median, 96.7%). With an additional dose of external beam radiotherapy (EBRT), the median D90 was 94 (range, 83-104) Gyα/β10 for HR-CTV and 77 (range, 70-87) Gyα/β10 for IR-CTV; the median dose delivered to 100% of the target volume (D100) was 75 (range, 66-84) Gyα/β10 for HR-CTV and 65 (range, 57-73) Gyα/β10 for IR-CTV. The minimum dose to the most irradiated 2 cc volume (D2cc) was 73-96 (median, 83) Gyα/β3 for the bladder, 64-98 (median, 73) Gyα/β3 for the rectum, and 52-69 (median, 61) Gyα/β3 for the sigmoid colon. After a median follow-up of 15 months (range, 3-24 months), two patients experienced local failure, and 1 showed internal iliac nodal metastasis. Despite the relatively small number of needles used, CT-guided HDRISBT for cervical cancer showed favorable DVH parameters and clinical outcome.

American Brachytherapy Society consensus guidelines for locally advanced carcinoma of the cervix. Part II: high-dose-rate brachytherapy

PURPOSE

This report presents an update to the American Brachytherapy Society (ABS) high-dose-rate (HDR) brachytherapy guidelines for locally advanced cervical cancer.

METHODS

Members of the ABS with expertise in cervical cancer formulated updated guidelines for HDR brachytherapy using tandem and ring, ovoids, cylinder, or interstitial applicators for locally advanced cervical cancer. These guidelines were written based on medical evidence in the literature and input of clinical experts in gynecologic brachytherapy.

RESULTS

The ABS affirms the essential curative role of tandem-based brachytherapy in the management of locally advanced cervical cancer. Proper applicator selection, insertion, and imaging are fundamental aspects of the procedure. Three-dimensional imaging with magnetic resonance or computed tomography or radiographic imaging may be used for treatment planning. Dosimetry must be performed after each insertion before treatment delivery. Applicator placement, dose specification, and dose fractionation must be documented, quality assurance measures must be performed, and followup information must be obtained. A variety of dose/fractionation schedules and methods for integrating brachytherapy with external-beam radiation exist. The recommended tumor dose in 2-Gray (Gy) per fraction radiobiologic equivalence (normalized therapy dose) is 80-90Gy, depending on tumor size at the time of brachytherapy. Dose limits for normal tissues are discussed.

CONCLUSION

These guidelines update those of 2000 and provide a comprehensive description of HDR cervical cancer brachytherapy in 2011.

Comparison of 3D MRI with high sampling efficiency and 2D multiplanar MRI for contouring in cervix cancer brachytherapy

Background

MRI sequences with short scanning times may improve accessibility of image guided adaptive brachytherapy (IGABT) of cervix cancer. We assessed the value of 3D MRI for contouring by comparing it to 2D multi-planar MRI.

Patients and methods

In 14 patients, 2D and 3D pelvic MRI were obtained at IGABT. High risk clinical target volume (HR CTV) was delineated by 2 experienced radiation oncologists, using the conventional (2D MRI-based) and test (3D MRI-based) approach. The value of 3D MRI for contouring was evaluated by using the inter-approach and inter-observer analysis of volumetric and topographic contouring uncertainties. To assess the magnitude of deviation from the conventional approach when using the test approach, the inter-approach analysis of contouring uncertainties was carried out for both observers. In addition, to assess reliability of 3D MRI for contouring, the impact of contouring approach on the magnitude of inter-observer delineation uncertainties was analysed.

Results

No approach- or observer - specific differences in HR CTV sizes, volume overlap, or distances between contours were identified. When averaged over all delineated slices, the distances between contours in the inter-approach analysis were 2.6 (Standard deviation (SD) 0.4) mm and 2.8 (0.7) mm for observers 1 and 2, respectively. The magnitude of topographic and volumetric inter-observer contouring uncertainties, as obtained on the conventional approach, was maintained on the test approach. This variation was comparable to the inter-approach uncertainties with distances between contours of 3.1 (SD 0.8) and 3.0 (SD 0.7) mm on conventional and test approach, respectively. Variation was most pronounced at caudal HR CTV levels in both approaches and observers.

Conclusions

3D MRI could potentially replace multiplanar 2D MRI in cervix cancer IGABT, shortening the overall MRI scanning time and facilitating the contouring process, thus making this treatment method more widely employed.

Image and laparoscopic guided interstitial brachytherapy for locally advanced primary or recurrent gynaecological cancer using the adaptive GEC ESTRO target concept

PURPOSE

To retrospectively assess treatment outcome of image and laparoscopic guided interstitial pulsed dose rate brachytherapy (PDR-BT) for locally advanced gynaecological cancer using the adaptive GEC ESTRO target concept.

MATERIALS AND METHODS

Between June 2005 and December 2010, 28 consecutive patients were treated for locally advanced primary vaginal (nine), recurrent endometrial (12) or recurrent cervical cancer (seven) with combined external beam radiotherapy (EBRT) and interstitial PDR-BT. Treatment was initiated with whole pelvic EBRT to a median dose of 45 Gy followed by PDR-BT using the Martinez Universal Perineal Interstitial Template (MUPIT). All implants were virtually preplanned using MRI of the pelvis with a dummy MUPIT in situ. The GEC ESTRO high risk clinical target volume (HR CTV), intermediate risk clinical target volume (IR CTV) and the organs at risk (OAR) were contoured and a preplan for implantation was generated (BrachyVision, Varian). The subsequent implantation was performed under laparoscopic visualisation. Final contouring and treatment planning were done using a post-implant CT. Planning aim of PDR-BT was to deliver 30 Gy in 50 hourly pulses to HR CTV. Manual dose optimisation was performed with the aim of reaching a D90>80 Gy in the HR CTV calculated as the total biologically equivalent to 2 Gy fractions of EBRT and BT (EQD2). Dose to the OAR were evaluated using dose volume constraints for D(2cc) of 90 Gy for bladder and 70 Gy for rectum and sigmoid.

RESULTS

For HR CTV the median volume was 26 cm(3) (7-91 cm(3)). Coverage of the HR CTV was 97% (90-100%) and D90 was 82 Gy (77-88 Gy). The D(2cc) for bladder, rectum, and sigmoid were 65 Gy (47-81 Gy), 61 Gy (50-77 Gy), and 52 Gy (44-68 Gy), respectively. Median follow up was 18 months (6-61 months). The actuarial 2 years local control rate was 92% (SE 5), while disease-free survival and overall survival were 59% (SE 11) and 74%, respectively (SE 10). No complications to the laparoscopic guided implantation were encountered. Late grade 2 (CTC v 3.0) complications were recorded in nine (32%) patients. One patient had a grade 3 vaginal complication. No grade 4-5 complications have been recorded so far.

CONCLUSION

Image and laparoscopic guided interstitial PDR-BT using the GEC ESTRO target concept is applicable for locally advanced primary vaginal or recurrent endometrial and cervical cancer resulting in an excellent local control rate and limited morbidity.