MRI assessment of cervical cancer for adaptive radiotherapy

Prospective validation of a machine learning model for applicator and hybrid interstitial needle selection in high-dose-rate (HDR) cervical brachytherapy

PURPOSE

To Demonstrate the clinical validation of a machine learning (ML) model for applicator and interstitial needle prediction in gynecologic brachytherapy through a prospective clinical study in a single institution.

METHODS

The study included cervical cancer patients receiving high-dose-rate brachytherapy using intracavitary (IC) or hybrid interstitial (IC/IS) applicators. For each patient, the primary radiation oncologist contoured the high-risk clinical target volume on a pre-brachytherapy MRI, indicated the approximate applicator location, and made a clinical determination of the first fraction applicator. A pre-trained ML model predicted the applicator and IC/IS needle arrangement using tumor geometry. Following the first fraction, ML and radiation oncologist predictions were compared and a replanning study determined the applicator providing optimal organ-at-risk (OAR) dosimetry. The ML-predicted applicator and needle arrangement and the clinical determination were compared to this dosimetric ground truth.

RESULTS

Ten patients were accrued from December 2020 to October 2022. Compared to the dosimetrically optimal applicator, both the radiation oncologist and ML had an accuracy of 70%. ML demonstrated better identification of patients requiring IC/IS applicators and provided balanced IC and IC/IS predictions. The needle selection model achieved an average accuracy of 82.5%. ML-predicted needle arrangements matched or improved plan quality when compared to clinically selected arrangements. Overall, ML predictions led to an average total improvement of 2.0 Gy to OAR doses over three treatment fractions when compared to clinical predictions.

CONCLUSION

In the context of a single institution study, the presented ML model demonstrates valuable decision-support for the applicator and needle selection process with the potential to provide improved dosimetry. Future work will include a multi-center study to assess generalizability.

Method to assess the need for re-planning HDR brachytherapy tandem and ring treatments

High dose rate (HDR) brachytherapy procedures for cervical cancer require multiple applicator insertions for multiple (typically 5) fractions of a single plan, which carries a risk for variability in applicator position between fractions. Due to applicator displacement relative to patient anatomy, the dose to nearby organs-at-risk (OARs) may vary significantly from one fraction to the next. The purpose of this study was to evaluate the effect of changes in HDR tandem and ring (T&R) applicator position on doses to nearby OARs and to present a quick and simple method to estimate doses to OARs inter-fractionally without having to perform a re-plan. Ninety CT image sets for 20 patients, ages 44 to 86, undergoing T&R-based HDR for cervical cancer were used retrospectively for this study. Measures of applicator positional and angular changes relative to the bony anatomy were obtained using image fusion in MIM software, between the planning CT (plan CT) and the CT on the treatment day (CT-TX). Dosimetric data were determined, also using MIM software, using the original (first fraction) dose distribution applied to organs at risk (rectum and bladder), transferred via rigid registration from the plan CT to each CT-TX. Bladder and rectum contours were also transferred from each plan CT to each CT-TX and were tweaked manually to match anatomy on each CT-TX and examined visually for appropriateness. Differences in translation and rotation of the T&R applicator between the planning CT and subsequent individual fractions were recorded and plotted against dose differences between each fraction of treatment and the original (first) fraction. Absolute dose (D2cc) and volume (V50) differences vs positional shifts were calculated and plotted, and the Pearson Product-Moment correlation coefficient between dose parameters and measured positional shifts was determined. Average dosimetric differences between planned dose and subsequent fractional doses obtained through rigid registration were 1.48 ± 1.92 Gy, 14.91 ± 11.92 cm3, 0.56 ± 0.93 Gy, and 1.77 ± 2.18 cm3 for Bladder D2cc, Bladder V50, Rectum D2cc, and Rectum V50, respectively. Correlation between Bladder V50 and sagittal plane rotation gave an r2 of 0.4, showing the most correlation of all parameters studied. Bladder dose and volume increased by a maximum of about 2.7 Gy and 50 cm3 overall for Bladder D2cc and Bladder V50, respectively. Bladder V50 was most sensitive to T&R applicator displacements. We have quantified the effects of applicator positional changes on dose changes for the bladder and rectum. Even large changes in applicator position between fractions did not result in significant changes in dose to these normal tissues, indicating that adaptive re-planning is not necessary.

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

Background and purpose

Image-guided adapted brachytherapy (IGABT) is superior to other radiotherapy techniques in the treatment of locally advanced cervical cancer (LACC). We aimed to investigate the benefit of interstitial needles (IN) for a combined intracavitary/interstitial (IC/IS) approach using IGABT over the intracavitary approach (IC) alone in patients with LACC after concomitant external beam radiotherapy (EBRT) and chemotherapy.

Materials and methods

We included consecutive patients with LACC who were treated with IC/IS IGABT after radiochemotherapy (RCT) in our retrospective, observational study. Dosimetric gain and sparing of organs at risk (OAR) were investigated by comparing the IC/IS IGABT plan with a simulated plan without needle use (IC IGABT plan) and the impact of other clinical factors on the benefit of IC/IS IGABT.

Results

Ninety-nine patients were analyzed, with a mean EBRT dose of 45.5 ± 1.7 Gy; 97 patients received concurrent chemotherapy. A significant increase in median D90% High Risk Clinical target volume (HR-CTV) was found for IC/IS (82.8 Gy) vs IC (76.2 Gy) (p < 10-4). A significant decrease of the delivered dose for all OAR was found for IC/IS vs IC for median D2cc to the bladder (77.2 Gy), rectum (68 Gy), sigmoid (53.2 Gy), and small bowel (47 Gy) (all p < 10-4).

Conclusion

HR-CTV coverage was higher with IC/IS IGABT than with IC IGABT, with lower doses to the OAR in patients managed for LACC after RCT. Interstitial brachytherapy in the management of LACC after radiotherapy provides better coverage of the target volumes, this could contribute to better local control and improved survival of patients.

Prognostic Implications of Uterine Cervical Cancer Regression During Chemoradiation Evaluated by the T-Score in the Multicenter EMBRACE I Study

PURPOSE

A simple scoring system (T-score, TS) for integrating findings from clinical examination and magnetic resonance imaging (MRI) of the primary tumor at diagnosis has shown strong prognostic capability for predicting local control and survival in locally advanced cervical cancer treated with chemoradiation and MRI-guided brachytherapy (BT). The aim was to validate the performance of TS using the multicenter EMBRACE I study and to evaluate the prognostic implications of TS regression obtained during initial chemoradiation.

METHODS AND MATERIALS

EMBRACE I recruited 1416 patients, of whom 1318 were available for TS. Patients were treated with chemoradiation followed by MRI-guided BT. A ranked ordinal scale of 0 to 3 points was used to assess 8 anatomic locations typical for local invasion of cervical cancer. TS was calculated separately at diagnosis (TSD) and at BT (TSBT) by the sum of points obtained from the 8 locations at the 2 occasions.

RESULTS

Median TSD and TSBT was 5 and 4, respectively. TS regression was observed in 71% and was an explanatory variable for BT technique (intracavitary vs intracavitary/interstitial) and major dose-volume histogram parameters for BT, such as high-risk clinical target (CTVHR), CTVHR D90 (minimal dose to 90% of the target volume), D2cm3 bladder (minimal dose to the most exposed 2 cm3 of the bladder), and D2cm3 rectum. TS regression (TSBT≤5) was associated with improved local control and survival and with less morbidity compared with patients with TSBT remaining high (>5) despite initial chemoradiation. TS regression was significant in multivariate analysis for both local control and survival when analyzed in consort with already established prognostic parameters related to the patient, disease, and treatment.

CONCLUSIONS

TS was validated in a multicenter setting and proven to be a strong multidisciplinary platform for integration of clinical findings and imaging with the ability to quantitate local tumor regression and its prognostic implications regarding BT technique, dose-volume histogram parameters, local control, survival, and morbidity.

Radiotherapy for cervical cancer: Chilean consensus of the Society of Radiation Oncology

Background

Cervical cancer is a public health problem in Latin America. Radiotherapy plays a fundamental role both as definitive or adjuvant treatment. There are important intra and inter-country differences regarding access and availability of radiotherapy facilities in this region. The aim of a study was to standardize the basic clinical and technical criteria for the radiation treatment of patients with CC in Chile and provide a guide for Latin American Radiation Oncologists.

Materials and methods

Forty-one expert radiation oncologists from the Chilean Radiation Oncology Society made a consensus using the Delphi methodology.

Results

There was a high degree of agreement for each of the recommendations. Those with the lowest percentage were related to the definition of the conformal 3D technique as the standard for definitive external radiotherapy (81%) and the criteria for extended nodal irradiation (85%).

Conclusions

These recommendations present an updated guide for radiotherapy treatment of patients with cervical cancer for Latin America. Those should be implemented according to local resources of each institution.

Multi-Habitat Based Radiomics for the Prediction of Treatment Response to Concurrent Chemotherapy and Radiation Therapy in Locally Advanced Cervical Cancer

Objectives: To develop a radiomic model based on multiparametric magnetic resonance imaging (MRI) for predicting treatment response prior to commencing concurrent chemotherapy and radiation therapy (CCRT) for locally advanced cervical cancer.

Materials and methods: The retrospective study enrolled 120 patients (allocated to a training or a test set) with locally advanced cervical cancer who underwent CCRT between December 2014 and June 2017. All patients enrolled underwent MRI with nine sequences before treatment and again at the end of the fourth week of treatment. Responses were evaluated by MRI according to RECIST standards, and patients were divided into a responder group or non-responder group. For every MRI sequence, a total of 114 radiomic features were extracted from the outlined tumor habitat. On the training set, the least absolute shrinkage and selection operator method was used to select key features and to construct nine habitat signatures. Then, three kinds of machine learning models were compared and applied to integrate these predictive signatures and the clinical characteristics into a radiomic model. The discrimination ability, reliability, and calibration of our radiomic model were evaluated.

Results: The radiomic model, which consisted of three habitat signatures from sagittal T2 image, axial T1 enhanced-MRI image, and ADC image, respectively, has shown good predictive performance, with area under the curve of 0.820 (95% CI: 0.713–0.927) in the training set and 0.798 (95% CI: 0.678–0.917) in the test set. Meanwhile, the model proved to perform better than each single signature or clinical characteristic.

Conclusions: A radiomic model employing features from multiple tumor habitats held the ability for predicting treatment response in patients with locally advanced cervical cancer before commencing CCRT. These results illustrated a potential new tool for improving medical decision-making and therapeutic strategies.

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.

Patterns of cervical cancer brachytherapy in India: results of an online survey supported by the Indian Brachytherapy Society

PURPOSE

Cervical cancer is the most common gynecological cancer in India. Uniform protocol-based treatment is important for achieving optimal outcomes. We undertook a survey to investigate patterns of care with special regard to patterns of care in cervical cancer brachytherapy in India.

MATERIAL AND METHODS

A 17-question online survey was sent to radiation oncologists across India. Respondents were required to have a minimum of 1-year experience. One response per center was accepted and deemed as representative.

RESULTS

Out of 116 centers, 59 responses were generated. Two-thirds (66.1%) were from academic centers and the majority (96.6%) used high-dose-rate (HDR) brachytherapy. The centers treated an average of 255 patients per year (median 161 patients, IQR 76-355). The majority were locally advanced cancers (FIGO 2009 stage II-IV 87.5%). External beam radiotherapy (EBRT) schedules were fairly consistent, administering doses of 45-50 Gy over 5 weeks. Brachytherapy was performed towards EBRT completion by 37/59 (62%) and 43/59 (74.3%) centers used a schedule of 7 Gy × 4 fractions (HDR). Brachytherapy was commonly performed under anesthesia (spinal/general: 44% each) with ultrasound (USG) guidance (29%). Computed tomography (CT) imaging (65%) and orthogonal X-rays (35%) represented the most common imaging for planning, while point A prescription (66%) or GEC-ESTRO based parameters (35%) with manual/geometric methods represented the most common methodology for dose volume prescription and optimization. Overall treatment time (OTT) reported was within 49-56 days in 50%. Complex implants (IC + IS) were performed for more than 30% of cases by 3 centers.

CONCLUSIONS

Our survey suggested a fairly uniform treatment paradigm for cervical cancer brachytherapy, with a progressive shift from 2D to 3D image-based parameters for planning, with persistence of point A based prescription. Further efforts are needed to augment and ease this transition.

Prospective intra/inter-observer evaluation of pre-brachytherapy cervical cancer tumor width measured in TRUS and MR imaging

BACKGROUND

Ultrasound (US) imaging has been proved as an excellent diagnostic tool in gynecology and, due to its wide availability and limited cost, is under intense investigation as base for dose adaptation in cervical cancer brachytherapy. Purpose of this work is to test inter/intra-observer uncertainties between magnetic resonance (MR) and trans-rectal ultrasound (TRUS) imaging in defining maximum tumor width before first brachytherapy (BT) application in a prospective cohort of cervical cancer patients undergoing image-guided adaptive brachytherapy (IGABT).

METHODS

One hundred ten consecutive cervical cancer patients treated between 2013 and 2016 were included. Before the first BT implant patients underwent MR and TRUS scan with no applicator in place. Images were independently analyzed by three examiners, blinded to the other's results. With clinical information at hand, maximum tumor width was measured on preBT TRUS and MR. Quantitative agreement analysis was undertaken. Intra-class correlation coefficient (ICC), Passing-Bablok and Bland Altman plots were used to evaluate the intra/inter-observers measurement agreement.

RESULTS

Average difference between tumor width measured on MR (HRCTV_MR) and TRUS (HRCTV_TRUS) was 1.3 ± 3.2 mm (p <  0.001); 1.1 ± 4.6 mm (p = 0.01) and 0.7 ± 3 mm (p = 0.01). The error was less than 3 mm in 79, 82 and 80% of the measurements for the three observers, respectively. Intra-observer ICC was 0.96 (CI95% 0.94-0.97), 0.93 (CI95% 0.9-0.95) and 0.96 (CI95% 0.95-0.98) respectively. Inter-observer ICC for HRCTV_MR width measures was 0.92 (CI95% 0.89-0.94) with no difference among FIGO stages. Inter-observer ICC for HRCTV_TRUS was 0.86 (CI95% 0.81-0.9). For FIGO stage I and II tumors, ICC HRCTV_TRUS values were comparable to respective HRCTV_MR ICC values. For larger tumors HRCTV_TRUS inter-observer ICC values were lower than respective HRCTV_MR although remaining acceptable.

CONCLUSIONS

Our results suggest that TRUS is equivalent to MR in assessing preBT tumor maximum width in cervical cancer FIGO stage I/II. In more advanced stages TRUS seems to be slightly inferior to MR although maintaining a good agreement to gold standard imaging.

A hybrid technique of intracavitary and interstitial brachytherapy for locally advanced cervical cancer: initial outcomes of a single-institute experience

BACKGROUND

Locally advanced uterine cervical cancer (LAUCC) with lateral tumor extension may not always be covered adequately by conventional intracavitary brachytherapy (ICBT). Hybrid intracavitary and interstitial brachytherapy (HBT) seems to be an effective alternative by improving anatomy-oriented dose optimisation. The purpose of this study was to report initial clinical result for LAUCC treated by HBT.

METHODS

Between January 2012 and November 2015, 42 patients with LAUCC (T1b2-4a) were treated with primary radiation therapy including HBT. Patients with distant metastasis other than para-aortic lymph node spread were excluded from this study. A retrospective analysis was performed for toxicity evaluation and oncological outcome calculation.

RESULTS

Median follow-up was 23.2 months (range 13.2-71.4). Two-year overall survival, progression free survival, and local control rate were 81.6, 54.4, and 80.2%, respectively. Seven patients experienced local recurrence (16.6%). Of those, five were confined to the uterus and two at the parametria. Late adverse events ≥ grade 3 were seen in 3 patients.

CONCLUSIONS

HBT can generate favorable local control in tumors which cannot be adequately covered by ICBT.

Magnetic resonance imaging after external beam radiotherapy and concurrent chemotherapy for locally advanced cervical cancer helps to identify patients at risk of recurrence

OBJECTIVE

Tumor volume and regression after external beam radiotherapy have been shown to be accurate parameters to assess treatment response via magnetic resonance imaging (MRI). The aim of the study was to evaluate the prognostic value of tumor size reduction rate after external beam radiotherapy and chemotherapy prior to brachytherapy.

METHODS

Patients with locally advanced cervical cancer treated at two French comprehensive cancer centers between 1998 and 2010 were included. Treatment was pelvic external beam radiotherapy with platinum based chemotherapy followed by brachytherapy. Records were reviewed for demographic, clinical, imaging, treatment, and follow-up data. Anonymized linked data were used to ascertain the association between pre-external and post-external beam radiotherapy MRI results, and survival data.

RESULTS

185 patients were included in the study. Median age at diagnosis was 45 years (range 26-72). 77 patients (41.6%) were International Federation of Gynecology and Obstetrics stage IB2-IIA disease and 108 patients (58.4%) were stage IIB-IVA. Median tumor size after external beam radiotherapy and chemotherapy was 2.0 cm (range 0.0-8.0) and median tumor size reduction rate was 62.4% (range 0.0-100.0%). Tumor size and tumor reduction rate at 45 Gy external beam radiotherapy MRI were significantly associated with local recurrence free survival (P<0.001), disease free survival, and overall survival (P<0.05). Tumor reduction rate ≥60% was significantly associated with a decreased risk of relapse and death (HR (95% CI) 0.21 (0.09 to 0.50), P=0.001 for local recurrence free survival; 0.48 (0.30 to 0.77) P=0.002 for disease free survival; and 0.51 (0.29 to 0.88), P=0.014 for overall survival).

CONCLUSIONS

Tumor size reduction rate >60% between pre-therapeutic and post-therapeutic 45 Gy external beam radiotherapy with concurrent chemotherapy was associated with improved survival. Future studies may help to identify patients who may ultimately benefit from completion surgery, adjuvant chemotherapy, and closer follow-up.

Changes in Tumor Biology During Chemoradiation of Cervix Cancer Assessed by Multiparametric MRI and Hypoxia PET

PURPOSE

Imaging biomarkers assessed with magnetic resonance imaging (MRI) and/or positron emission tomography (PET) enable non-invasive tumor characterization in cervix cancer patients. We investigated the spatio-temporal stability of hypoxia, perfusion, and the cell density of tumors over time by repetitive imaging prior to, during, and after radio-chemotherapy.

PROCEDURES

Thirteen patients were included in this prospective study. The imaging protocol included the following: [¹⁸F]fluoromisonidazole ([¹⁸F]FMISO)-PET/x-ray computed tomography (CT) and multiparametric (mp)-MRI at four time-points (TP): baseline (BL); and weeks 2 (TP1), 5 (TP2), and 19 after treatment start (follow-up FU). Complete datasets for six patients could be assessed for tumor volume, enhancement kinetics, diffusivity, and [¹⁸F]FMISO-avidity (P1-P6). In addition, two patients completed all PET/CT examinations (P7-P8) but not all MR scans; however, one of them had no hypoxia (P8). Descriptive statistics, correlations, and voxel-by-voxel analysis were performed. For various, independent reasons, five patients could not complete the study according to the protocol with all imaging sequences.

RESULTS

Median tumor ADCs (in ×10^-3 mm²/s) were 0.99 ± 0.10 at BL, 1.20 ± 0.12 at TP1, 1.33 ± 0.14 at TP2, and 1.38 ± 0.21 at FU. The median TBR_peak (tumor-to-background) was 2.7 ± 0.8 at BL, 1.6 ± 0.2 at TP1, 1.8 ± 0.3 at TP2, and 1.7 ± 0.3 at FU. The voxel-by-voxel analysis of the [¹⁸F]FMISO uptake at BL and TP1 showed no correlation. Between TP2 and TP1 and FU and TP2, weak correlations were found for two patients.

CONCLUSIONS

Longitudinal mp-MR and PET imaging enables the in vivo tumor characterization over time. While perfusion and cell density decreased, there was a non-uniform change of hypoxia observed during radiotherapy. To assess the potential impact with regard to more personalized treatment approaches, hypoxia imaging-based dose painting for cervix cancer requires further research.

The Potential Value of MRI in External-Beam Radiotherapy for Cervical Cancer

The reference standard treatment for cervical cancer is concurrent chemoradiotherapy followed by magnetic resonance imaging (MRI)-guided brachytherapy. Improvements in brachytherapy have increased local control rates, but late toxicity remains high with rates of 11% grade ≥3. The primary clinical target volume (CTV) for external-beam radiotherapy includes the cervix and uterus, which can show significant inter-fraction motion. This means that generous margins are required to cover the primary CTV, increasing the radiation dose to organs at risk and, therefore, toxicity. A number of image-guided radiotherapy techniques (IGRT) have been developed, but motion can be random and difficult to predict prior to treatment. In light of the development of integrated MRI linear accelerators, this review discusses the potential value of MRI in external-beam radiotherapy. Current solutions for managing pelvic organ motion are reviewed, including the potential for online adaptive radiotherapy. The impacts of the use of MRI in tumour delineation and in the delivery of stereotactic ablative body radiotherapy (SABR) are highlighted. The potential role and challenges of using multi parametric MRI to guide radiotherapy are also discussed.

Off-line magnetic resonance imaging navigation of cervix cancer brachytherapy in patients with risk factors for uterine perforation

Purpose

There are no reports on pre-insertion identification of cervix cancer patients at risk for uterine perforation during brachytherapy (BT). Our aim was to assess the incidence of risk factors in our patient cohort, and assess feasibility of a novel technique of magnetic resonance imaging (MRI)-guided navigation for applicator insertion (NAI) in high-risk cases.

Material and methods

All patients with locally advanced cervical cancer, treated with image guided adaptive BT at our department between October 2013 and June 2017 were considered for analysis. Tumor characteristics on initial MRI (MRI_initial), pre-BT MRI (MRI_pre-BT), and BT MRI (MRI_BT) were assessed. Frequency of risk factors (age above 60 years, retroverted/retroflected uterus, tumor necrosis, non-visible cervical orifice, distorted cervical canal) was recorded. Patients with two or more factors underwent MRI guided NAI. Time needed for NAI was estimated and procedure feasibility score assigned using a three-tiered scoring system.

Results

Twenty-seven patients (98 insertions) were included. Mean tumor volume was 70.2 (± 47.9), 17.8 (± 18.9), and 10.3 (± 9.1) cm³ on MRI_initial, MRI_pre-BT, and MRI_BT1, respectively (p < 0.05). In 16 (59%) cases, ≥ 1 perforation risk factor was found on MRI_pre-BT: distorted canal in 12 (44%), necrosis in 9 (33%), retroverted/retroflected uterus in 8 (30%) cases. Nine (33%) patients had ≥ 2 risk factors and underwent MRI guided NAI. Additional time to perform NAI was estimated at 105 minutes, and feasibility score was 1 in all cases. There were no cases of uterine perforation.

Conclusions

Using pre-insertion MRI, we found ≥ 2 risk factors for uterine perforation in 1/3 of patients. Off-line MRI navigation was feasible and enabled non-complicated insertion in all cases. Further studies with larger sample size are warranted to assess its clinical efficacy.

Quantitative CT assessment of a novel direction-modulated brachytherapy tandem applicator

PURPOSE

The purpose of this study was to quantitatively assess the CT metal-induced artifacts from a novel direction-modulated brachytherapy (DMBT) tandem applicator prototype, recently designed for cervical cancer treatments.

METHODS AND MATERIALS

A water-based pelvic phantom was constructed for CT scanning. The DMBT applicator was imaged using our institutional protocol, one with higher kVp and mAs settings, and repetition of these protocols using 3-mm slices. A conventional stainless steel applicator was also scanned. In addition to the standard reconstructed images, applicator images were reconstructed using a commercial metal artifact-reduction (MAR) algorithm and an in-house-developed research algorithm. Subsequently, image quality and artifact severity were evaluated.

RESULTS

Artifact severity, measured in terms of SDs in CT numbers, decreased asymptotically to background water levels with the distance away from the applicator. Artifact-reduction algorithms lead to significant and visible improvements in image quality, with >50% and >20% decrease in artifact severity achieved at a 10-mm distance for the DMBT and stainless steel applicators, respectively. Differences in artifact severity were minimal between the four imaging protocols. DMBT dimensions were the same on images with and without the commercial MAR algorithm, within <1 mm of the theoretical value. Both the commercial and in-house algorithms restored the CT numbers outside the applicator, albeit a better performance was achieved by the in-house algorithm.

CONCLUSIONS

The artifacts produced by both applicators were minimized with the use of MAR algorithms. Adoption of the DMBT and stainless steel applicators for CT-guided brachytherapy is anticipated as MAR algorithms are widely available on CT scanners.

MR Imaging in Gynecologic Brachytherapy

Magnetic resonance-based image-guided adaptive brachytherapy is gaining popularity in the United States in the setting of gynecologic malignancies. This technique improves local control, increases overall survival, and minimizes toxicity to the adjacent organs at risk. The purpose of this article is to familiarize radiologists with image-guided adaptive brachytherapy by describing its history, detailing MR imaging techniques, describing treatment considerations, and reviewing image interpretation.

Advancements in brachytherapy

Brachytherapy is a radiotherapy modality associated with a highly focal dose distribution. Brachytherapy treats the cancer tissue from the inside, and the radiation does not travel through healthy tissue to reach the target as with external beam radiotherapy techniques. The nature of brachytherapy makes it attractive for boosting limited size target volumes to very high doses while sparing normal tissues. Significant developments over the last decades have increased the use of 3D image guided procedures with the utilization of CT, MRI, US and PET. This has taken brachytherapy to a new level in terms of controlling dose and demonstrating excellent clinical outcome. Interests in focal, hypofractionated and adaptive treatments are increasing, and brachytherapy has significant potential to develop further in these directions with current and new treatment indications.

Implementation of image-guided brachytherapy (IGBT) for patients with uterine cervix cancer: a tumor volume kinetics approach

Purpose

To evaluate tumor shrinking kinetics in order to implement image-guided brachytherapy (IGBT) for the treatment of patients with cervix cancer.

Material and methods

This study has prospectively evaluated tumor shrinking kinetics of thirteen patients with uterine cervix cancer treated with combined chemoradiation. Four high dose rate brachytherapy fractions were delivered during the course of pelvic external beam radiation therapy (EBRT). Magnetic resonance imaging (MRI) exams were acquired at diagnosis (D), first (B1), and third (B3) brachytherapy fractions. Target volumes (GTV and HR-CTV) were calculated by both the ellipsoid formula (VE) and MRI contouring (VC), which were defined by a consensus between at least two radiation oncologists and a pelvic expert radiologist.

Results

Most enrolled patients had squamous cell carcinoma and FIGO stage IIB disease, and initiated brachytherapy after the third week of pelvic external beam radiation. Gross tumor volume volume reduction from diagnostic MRI to B1 represented 61.9% and 75.2% of the initial volume, when measured by VE and VC, respectively. Only a modest volume reduction (15-20%) was observed from B1 to B3.

Conclusions

The most expressive tumor shrinking occurred in the first three weeks of oncological treatment and was in accordance with gynecological examination. These findings may help in IGBT implementation.

Factors Predictive of Protracted Course of Radiation Therapy in Patients Treated with Definitive Chemoradiation for Cervical Cancer

Background

There is a benefit to completing definitive chemoradiotherapy (CRT) for cervical cancer within 56 days. However, many patients experience delays due to missed radiation treatments that prolong the overall course of therapy. In order to improve patient care, we performed a quality improvement project to determine factors predictive of protracted treatment and develop strategies to enable timely treatment completion.

Methods 

Seventy-one patients treated for cervical cancer with CRT were identified. Medical records were reviewed to gather demographic, clinical, and treatment data. Prolonged treatment was defined as >56 days per the American Brachytherapy Society guidelines. The following variables were evaluated using paired t-tests and univariate logistic regression: demographics, Intensity Modulated Radiotherapy (IMRT) versus conventional radiation technique, use of a boost, time to stent placement, time to first brachytherapy (BT), and genitourinary (GU) or gastrointestinal (GI) toxicity.

Results

The median treatment length for all patients was 59 days. Factors associated with prolonged treatment were time to cervical stent placement (p=0.001), delay ≥2 days between final external beam radiation therapy (EBRT) and initial BT (p=0.0195), any grade GU toxicity (p=0.0007), or GI toxicity (p=0.0002), and the presence of a boost (p=0.0006). Age, stage, and IMRT versus conventional technique were not associated with protracted treatment.

Conclusion 

In this series of patients, acute toxicity, increased time to cervical stent placement, and time to first BT treatment were associated with prolonged treatment time. The patients who completed treatment in ≤56 days had a lower average time to cervical stent placement, 27 versus 31 days. Our results suggest that cervical stent placement during week four of treatment can enhance patient care and improve outcomes. 

A practical review of magnetic resonance imaging for the evaluation and management of cervical cancer

Cervical cancer is a leading cause of mortality in women worldwide. Staging and management of cervical cancer has for many years been based on clinical exam and basic imaging such as intravenous pyelogram and x-ray. Unfortunately, despite advances in radiotherapy and the inclusion of chemotherapy in the standard plan for locally advanced disease, local control has been unsatisfactory. This situation has changed only recently with the increasing implementation of magnetic resonance image (MRI)-guided brachytherapy. The purpose of this article is therefore to provide an overview of the benefits of MRI in the evaluation and management of cervical cancer for both external beam radiotherapy and brachytherapy and to provide a practical approach if access to MRI is limited.

45 or 50 Gy, Which is the Optimal Radiotherapy Pelvic Dose in Locally Advanced Cervical Cancer in the Perspective of Reaching Magnetic Resonance Image-guided Adaptive Brachytherapy Planning Aims?

AIMS

In locally advanced cervical cancer, the dose delivered results from the sum of external beam radiotherapy and brachytherapy, and is limited by the surrounding organs at risk. The balance between both techniques influences the total dose delivered to the high-risk clinical target volume (HR-CTV). The aim of the present study was to compare the ability of reaching different planning aims after external beam radiotherapy pelvic doses of 45 Gy in 25 fractions or 50.4 Gy in 28 fractions, both considered as standard prescriptions.

MATERIALS AND METHODS

The optimised plans of 120 patients treated with pelvic chemoradiation followed by magnetic resonance image-guided intracavitary brachytherapy were reviewed. The doses per pulse were calculated, and the number of pulses required to reach the planning aims, or a limiting dose constraint to organs at risk, was calculated. All doses were converted to 2-Gy equivalents. Three scenarios were applied consisting of different sets of planning aims: 85 and 60 Gy for the HR-CTV and the intermediate-risk CTV (IR-CTV) D90 (minimal dose received by 90% of the volume) in scenario 1, 90 and 60 Gy, respectively, for scenarios 2 and 3. For organs at risk, dose constraints were 90, 75 and 75 Gy to the bladder, rectum and sigmoid D2cm(3), respectively, in scenarios 1 and 2, and 80, 65 and 70 Gy in scenario 3.

RESULTS

A similar HR-CTV D90 could have been reached in scenarios 1 and 2 according to both pelvic doses. In scenario 3, a higher mean HR-CTV could have been reached in the 45 Gy arm (83.5 ± 8.0 versus 82.4 ± 8.0, P < 0.0001). The mean D2cm(3) of organs at risk was systematically and significantly increased after a delivery of 50.4 Gy to the pelvis, from 0.9 to 2.89 Gy. The proportions of plans reaching planning aims were 85.8, 72.5 and 42.5% after 45 Gy and 85.5, 67.5 and 33.3% after 50.4 Gy according to scenarios 1, 2 and 3, respectively. According to scenario 3, 50.4 Gy, the reachable HR-CTV D90 was higher in 30% of the cases, by 2 Gy in two cases. Those cases were unpredictable and due to unfavourable organs at risk topography and poor response to external beam radiotherapy.

CONCLUSION

The delivery of 45 Gy in 25 fractions to the pelvis before brachytherapy warrants a higher probability to reach brachytherapy planning aims, in comparison with 50.4 Gy in 28 fractions.

Hybrid (CT/MRI based) vs. MRI only based image-guided brachytherapy in cervical cancer: Dosimetry comparisons and clinical outcome

PURPOSE

Limited access to MRI has restricted implementation of MRI-based image-guided brachytherapy (IGBT) in line with GEC-ESTRO guidelines in many centers. This work reports our experience using an alternative CT/MRI based (hybrid) approach for IGBT, dosimetry comparisons, and its impact on long-term clinical outcome and major toxicity.

METHODS AND MATERIALS

Seventy-six patients diagnosed with locally advanced cervical cancer between May 2008 and May 2012 treated with IGBT were analyzed. The hybrid approach is the default IGBT approach during this study period. Forty-nine had hybrid approach and 27 patients had "3-fraction conformal MRI" approach (17 within EMBRACE study). Treatment consisted of 48 Gy in 24 fractions of conformally planned external beam radiotherapy with weekly cisplatin followed by three weekly fractions of brachytherapy to high-risk clinical target volume (HR-CTV). All patients have a prebrachytherapy MRI 4 days before treatment and with the applicators in place on Fraction 1. MRI only or CT is used for subsequent fractions. Using image registration techniques and the assumption that the HR-CTV is fixed with respect to the applicator, the HR-CTV from MRI at Fraction 1 is transferred onto subsequent fraction CT image sets for the hybrid approach.

RESULTS

Median follow-up was 41 months (range, 23-71 months). Excellent 3-year local control, overall progression-free survival, and overall survival of 92.6%, 78.8%, and 77.7% were seen with the hybrid approach and 92.2%, 66.3%, and 69.6% with a 3-fraction conformal MRI approach, respectively. Dosimetry achieved and late toxicity rates were comparable in the two groups.

CONCLUSIONS

Hybrid IGBT in locally advanced cervical cancer offers an alternative approach when access to MRI restricts implementation of IGBT.

Local experience in cervical cancer imaging: Comparison in tumour assessment between TRUS and MRI

OBJECTIVE

The aim of study was to analyze the accuracy of TRUS (transrectal ultrasound) vs. MRI (magnetic resonance imaging) and clinical gynecological examination estimation in the evaluation of tumor dimensions.

METHODS

The patients inclusion criterion included primarily pathologically squamous cell carcinoma, but excluded were patients who had not undergone BT (brachytherapy) and treated with palliative intent. We offer two types of treatment for locally advanced cervical cancer: (a) radiochemotherapy followed by surgery and (b) exclusive radiochemotherapy. Imaging tests follow the presence of tumor and tumor size (width and thickness). Each examination was performed by a different physician who had no knowledge of the others' findings. All patients underwent MRI prior to EBRT (external beam radiation therapy) while 18 of them also at the time of the first brachytherapy application. For the analysis we used the r-Pearson correlation coefficient.

RESULTS

In 2013, 26 patients with cervical cancer were included. A total of 44 gynecological examinations were performed, 44 MRIs and 18 TRUSs. For the comparisons prior to EBRT the correlation coefficient between TRUS vs. MRI was r = 0.79 for AP and r = 0.83 for LL, for GYN vs. MRI was r = 0.6 for AP and r = 0.75 for LL. Prior to BT for GYN vs. MRI, r values were 0.60 and 0.63 for AP and LL, respectively; for GYN vs. TRUS, r values were 0.56 and 0.78 for AP and LL, respectively.

CONCLUSIONS

A high correlation between the three examinations was obtained. As such, TRUS can be considered a suitable method in the evaluation of tumor dimensions.

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.

MRI findings at image guided adaptive cervix cancer brachytherapy: radiation oncologist's perspective

Magnetic resonance imaging (MRI) represents the reference imaging modality for image guided adaptive brachytherapy (IGABT) of cervix cancer. Accurate interpretation of pre-treatment MRI is required for proper understanding of the tumor extent and topography at IGABT. Planning and optimal timing of the application begins already before treatment, and may need to be adapted during external beam irradiation (EBRT) according to additional clinical and/or radiological findings. The level of MRI utilization in IGABT depends on the infrastructural capabilities of individual centers, ranging from no use at all to repetitive imaging during EBRT and each IGABT fraction. In this article, we summarize the role of different imaging modalities and practical aspects of MRI interpretation in cervix cancer IGABT, concentrating on the systematic evaluation of post-insertion images. MRI with the applicator in place from the radiation oncologist’s perspective should begin with immediate identification of eventual complications of the application procedure and assessment of the implant adequacy, followed by appropriate corrective measures in case of adverse findings. Finally, the tumor extent, topography, and treatment response should be evaluated in the context of initial clinical and radiological findings to allow for an appropriate selection and delineation of the target volumes.

MRI-guided adaptive radiotherapy in locally advanced cervical cancer from a Nordic perspective

BACKGROUND

The first Nordic protocol for three-dimensional (3D) planned radiotherapy in locally advanced cervical cancer was the prospective NOCECA study (1994-2000). NOCECA consisted of computed tomography (CT)-based 3D conformal external beam radiotherapy (EBRT) with a simultaneous integrated boost (SIB) to the primary tumour combined with brachytherapy (BT) based on x-ray imaging. In NOCECA the planning aim was to achieve 80 Gy at point A from EBRT and BT combined. However, the balance of dose between EBRT and BT was determined by tumour size at diagnosis with more EBRT dose given to point A and less by BT in more advanced stages. In 2005 image-guided adaptive brachytherapy (IGABT) based on magnetic resonance imaging (MRI) and optimisation of the BT dose distribution to the remaining tumour and cervix at time of BT (HR CTV) was introduced in Aarhus. EBRT remained like in NOCECA until 2008 when the SIB to the primary tumour was abandoned and IMRT was introduced as routine technique. In this study, we report outcome of our first five-year experience with IGABT using our NOCECA cohort as reference.

MATERIAL AND METHODS

The NOCECA cohort comprising 99 patients was compared with 140 consecutive patients treated by IGABT. Patients with para-aortic nodes were excluded in NOCECA but were present in 9% of the patients treated with IGABT. No patient in NOCECA received chemotherapy whereas concomitant cisplatin was given to 79% of the IGABT patients.

RESULTS

With IGABT actuarial local control was 91% at three years. When comparing NOCECA with IGABT overall survival was significantly improved from 63% to 79% (p = 0.005). In parallel, both moderate and severe late morbidity were reduced by about 50% (p = 0.02).

CONCLUSION

Introduction of IGABT reduced morbidity and generated a very high rate of local control, which likely has improved survival by at least as much as concomitant chemotherapy.

A level set based algorithm to reconstruct the urinary bladder from multiple views

The urinary bladder can be visualized from different views by imaging facilities such as computerized tomography and magnetic resonance imaging. Multi-view imaging can present more details of this pelvic organ and contribute to a more reliable reconstruction. Based on the information from multi-view planes, a level set based algorithm is proposed to reconstruct the 3D shape of the bladder using the cross-sectional boundaries. The algorithm provides a flexible solution to handle the discrepancies from different view planes and can obtain an accurate bladder surface with more geometric details.

Residual tumour volumes and grey zones after external beam radiotherapy (with or without chemotherapy) in cervical cancer patients. A low-field MRI study

BACKGROUND

Grey zones, which are defined as tissue with intermediate signal intensity in the area of primary hyperintense tumour extension, can be seen during radiation with or without chemotherapy on the T2-weighted MRI in patients with cervical cancer. The purpose of this study was to systematically measure the tumour volume at the time of diagnosis and the residual tumour volume at the time of brachytherapy without and with consideration of the grey zones and to estimate tumour regression during external beam radiotherapy (EBRT).

MATERIAL AND METHODS

T2-weighted MRI datasets of 175 patients with locally advanced cervical cancer (FIGO stage IB-IVA), who underwent combined external beam radiotherapy and brachytherapy with or without concomitant chemotherapy were available for this study. The gross tumour volume at the time of diagnosis (GTV(init)) and at the time of first brachytherapy without (GTV(res)) and with (GTV(res)+ GZ) consideration of grey zones were measured for each patient. A descriptive statistical analysis was performed and tumour regression rates without (R) and with consideration of grey zones (R(GZ)) were calculated. Further, the role of prognostic factors on GTV(init), GTV(res), GTV(res)+ GZ and tumour regression rates was investigated.

RESULTS

The median GTV(init), GTV(res), GTV(res)+ GZ in all patients were 44.4 cm(3), 8.2 cm(3), 20.3 cm(3), respectively. The median R was 78.5% and the median R(GZ) was 50.1%. The histology and FIGO staging showed a significant impact on GTV(init), GTV(res) and GTV(res)+ GZ.

CONCLUSION

Grey zones represent a substantial proportion of the residual tumour volume at the time of brachytherapy. Differentiation of high signal intensity mass and surrounding intermediate signal intensity grey zones may be reasonable.

Feasibility of transrectal ultrasonography for assessment of cervical cancer

PURPOSE

To retrospectively compare the maximum target width and target thickness in patients with locally advanced cervical cancer between magnetic resonance imaging (MRI) and transrectal ultrasonography (TRUS) in the course of primary radiochemotherapy.

PATIENTS AND METHODS

T2-weighted MRI and TRUS were performed on patients with locally advanced cervical cancer at the same timepoint-either at the time of diagnosis, or at the time of brachytherapy before or after insertion of the applicator. Patients treated from 2009 to 2011 were selected for this study based on the availability of MRI and TRUS at the defined time points. The target was defined as the complete macroscopic tumor mass and the remaining cervix and was measured on transversal planes. Descriptive statistics and a linear regression analysis were performed for the groups.

RESULTS

Images from 17 patients were available for analysis. Mean maximum target width was 4.2 ± 0.83 cm and 4.2 ± 0.79 cm for MRI and TRUS, respectively. Mean maximum target thickness was 3.3 ± 1.03 cm and 3.1 ± 1.15 cm for MRI and TRUS, respectively. Linear regression analysis for target width and thickness between TRUS and MRI demonstrated a correlation with R(2) = 0.842 and R(2) = 0.943, respectively.

CONCLUSION

The feasibility of TRUS for the assessment of local target extension could be demonstrated. Comparison of the target width and thickness showed a high correlation between TRUS and MRI, indicating the potential of TRUS for target definition in image-guided adaptive brachytherapy.

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.

MRI-based preplanning using CT and MRI data fusion in patients with cervical cancer treated with 3D-based brachytherapy: feasibility and accuracy study

PURPOSE

Magnetic resonance imaging (MRI)-assisted radiation treatment planning enables enhanced target contouring. The purpose of this study is to analyze the feasibility and accuracy of computed tomography (CT) and MRI data fusion for MRI-based treatment planning in an institution where an MRI scanner is not available in the radiotherapy department.

METHODS AND MATERIALS

The registration inaccuracy of applicators and soft tissue was assessed in 42 applications with CT/MRI data fusion. The absolute positional difference of the center of the applicators was measured in four different planes from the top of the tandem to the cervix. Any inaccuracy of registration of soft tissue in relation to the position of applicators was determined and dose-volume parameters for MRI preplans and for CT/MRI fusion plans with or without target and organs at risk (OAR) adaptation were evaluated.

RESULTS

We performed 6,132 measurements in 42 CT/MRI image fusions. Median absolute difference of the center of tandem on CT and MRI was 1.1 mm. Median distance between the center of the right ovoid on CT and MRI was 1.7 and 1.9 mm in the laterolateral and anteroposterior direction, respectively. Corresponding values for the left ovoid were 1.6 and 1.8 mm. Rotation of applicators was 3.1°. Median absolute difference in position of applicators in relation to soft tissue was 1.93, 1.50, 1.05, and 0.84 mm in the respective transverse planes, and 1.17, 1.28, 1.27, and 1.17 mm in selected angular directions. The dosimetric parameters for organs at risk on CT/MRI fusion plans without OAR adaptation were significantly impaired whereas the target coverage was not influenced. Planning without target adaptation led to overdosing of the target volume, especially high-risk clinical target volume--D₉₀ 88.2 vs. 83.1 (p < 0.05).

CONCLUSIONS

MRI-based preplanning with consecutive CT/MRI data fusion can be safe and feasible, with an acceptable inaccuracy of soft tissue registration.

Recommendations from Gynaecological (GYN) GEC-ESTRO Working Group (IV): Basic principles and parameters for MR imaging within the frame of image based adaptive cervix cancer brachytherapy

The GYN GEC-ESTRO working group issued three parts of recommendations and highlighted the pivotal role of MRI for the successful implementation of 3D image-based cervical cancer brachytherapy (BT). The main advantage of MRI as an imaging modality is its superior soft tissue depiction quality. To exploit the full potential of MRI for the better ability of the radiation oncologist to make the appropriate choice for the BT application technique and to accurately define the target volumes and the organs at risk, certain MR imaging criteria have to be fulfilled. Technical requirements, patient preparation, as well as image acquisition protocols have to be tailored to the needs of 3D image-based BT. The present recommendation is focused on the general principles of MR imaging for 3D image-based BT.

Methods and parameters have been developed and progressively validated from clinical experience from different institutions (IGR, Universities of Vienna, Leuven, Aarhus and Ljubljana) and successfully applied during expert meetings, contouring workshops, as well as within clinical and interobserver studies.

It is useful to perform pelvic MRI scanning prior to radiotherapy (“Pre-RT-MRI examination”) and at the time of BT (“BT MRI examination”) with one MR imager. Both low and high-field imagers, as well as both open and close magnet configurations conform to the requirements of 3D image-based cervical cancer BT. Multiplanar (transversal, sagittal, coronal and oblique image orientation) T2-weighted images obtained with pelvic surface coils are considered as the golden standard for visualisation of the tumour and the critical organs. The use of complementary MRI sequences (e.g. contrast-enhanced T1-weighted or 3D isotropic MRI sequences) is optional. Patient preparation has to be adapted to the needs of BT intervention and MR imaging. It is recommended to visualise and interpret the MR images on dedicated DICOM-viewer workstations, which should also assist the contouring procedure. Choice of imaging parameters and BT equipment is made after taking into account aspects of interaction between imaging and applicator reconstruction, as well as those between imaging, geometry and dose calculation.

In a prospective clinical context, to implement 3D image-based cervical cancer brachytherapy and to take advantage of its full potential, it is essential to successfully meet the MR imaging criteria described in the present recommendations of the GYN GEC-ESTRO working group.

MRI-based pre-planning in patients with cervical cancer treated with three-dimensional brachytherapy

OBJECTIVE

The aim of this study was to analyse the feasibility and determine the benefits of MRI-based pre-planning with CT/MRI data fusion in patients with cervical cancer treated with radical radiotherapy.

METHODS

Patients underwent MRI examination prior to external beam radiotherapy and prior to the first and fourth fraction of brachytherapy with applicators in place. Insertion of applicators at the radiology department was performed under paracervical anaesthesia. The benefit of MRI pre-planning was determined by comparing conventional treatment planning with dose specification to "point A" and dose specification to 90% of the high-risk clinical target volume (HR-CTV D90). Tolerance of MRI evaluation with applicators, coverage of HR-CTV and dose-volume parameters for organs at risk (OAR) has been assessed in 42 brachytherapy procedures.

RESULTS

Insertion of applicators at the radiology department was successful in all patients and there were no complications. The target dose was higher for MRI planning than for conventional planning (5.3 Gy vs 4.5 Gy). Maximum doses in the bladder and rectum were significantly lower (p<0.05) for MRI planning than for the conventional approach (6.49 Gy vs 7.45 Gy for bladder; 4.57 Gy vs 5.06 Gy for rectum). We found no correlation between the International Commission on Radiation Units (ICRU) point dose for OAR and the maximum dose in OAR. Nevertheless, a strong correlation between the maximum dose in OAR and the minimal dose in a volume of 2 cm(3) has been observed.

CONCLUSION

MRI-based pre-planning with consecutive CT/MRI data fusion is feasible and safe, with the advantage of increasing the dose to the tumour and decreasing the dose to the organs at risk.

Clinical outcome of protocol based image (MRI) guided adaptive brachytherapy combined with 3D conformal radiotherapy with or without chemotherapy in patients with locally advanced cervical cancer

Background

To analyse the overall clinical outcome and benefits by applying protocol based image guided adaptive brachytherapy combined with 3D conformal external beam radiotherapy (EBRT) ± chemotherapy (ChT).

Methods

Treatment schedule was EBRT with 45–50.4 Gy ± concomitant cisplatin chemotherapy plus 4 × 7 Gy High Dose Rate (HDR) brachytherapy. Patients were treated in the “protocol period” (2001–2008) with the prospective application of the High Risk CTV concept (D90) and dose volume constraints for organs at risk including biological modelling. Dose volume adaptation was performed with the aim of dose escalation in large tumours (prescribed D90 > 85 Gy), often with inserting additional interstitial needles. Dose volume constraints (D_2cc) were 70–75 Gy for rectum and sigmoid and 90 Gy for bladder.

Late morbidity was prospectively scored, using LENT/SOMA Score. Disease outcome and treatment related late morbidity were evaluated and compared using actuarial analysis.

Findings

One hundred and fifty-six consecutive patients (median age 58 years) with cervix cancer FIGO stages IB–IVA were treated with definitive radiotherapy in curative intent. Histology was squamous cell cancer in 134 patients (86%), tumour size was >5 cm in 103 patients (66%), lymph node involvement in 75 patients (48%). Median follow-up was 42 months for all patients.

Interstitial techniques were used in addition to intracavitary brachytherapy in 69/156 (44%) patients. Total prescribed mean dose (D90) was 93 ± 13 Gy, D_2cc 86 ± 17 Gy for bladder, 65 ± 9 Gy for rectum and 64 ± 9 Gy for sigmoid.

Complete remission was achieved in 151/156 patients (97%). Overall local control at 3 years was 95%; 98% for tumours 2–5 cm, and 92% for tumours >5 cm (p = 0.04), 100% for IB, 96% for IIB, 86% for IIIB. Cancer specific survival at 3 years was overall 74%, 83% for tumours 2–5 cm, 70% for tumours >5 cm, 83% for IB, 84% for IIB, 52% for IIIB. Overall survival at 3 years was in total 68%, 72% for tumours 2–5 cm, 65% for tumours >5 cm, 74% for IB, 78% for IIB, 45% for IIIB.

In regard to late morbidity in total 188 grade 1 + 2 and 11 grade 3 + 4 late events were observed in 143 patients. G1 + 2/G3 + 4 events for bladder were n = 32/3, for rectum n = 14/5, for bowel (including sigmoid) n = 3/0, for vagina n = 128/2, respectively.

Interpretation

3D conformal radiotherapy ± chemotherapy plus image (MRI) guided adaptive intracavitary brachytherapy including needle insertion in advanced disease results in local control rates of 95–100% at 3 years in limited/favourable (IB/IIB) and 85–90% in large/poor response (IIB/III/IV) cervix cancer patients associated with a moderate rate of treatment related morbidity. Compared to the historical Vienna series there is relative reduction in pelvic recurrence by 65–70% and reduction in major morbidity. The local control improvement seems to have impact on CSS and OS. Prospective clinical multi-centre studies are mandatory to evaluate these challenging mono-institutional findings.

Imaging technologies for high dose rate brachytherapy for cervical cancer: a systematic review

The aim of this overview was to assess the utility of various imaging technologies (fluoroscopy, ultrasound, computed tomography, magnetic resonance imaging and positron emission tomography) for the treatment planning of high dose rate brachytherapy for cervical cancer. Reviews and primary studies comparing different imaging technologies used during high dose rate brachytherapy for cervical cancer and published from 1988 to 2008 were sought by searching MEDLINE and EMBASE databases, the Cochrane Library, personal files and reference lists of identified studies, and by contacting experts. Study selection, study quality assessment and data extraction were carried out in duplicate. Twelve studies met the inclusion criteria. No systematic reviews or randomised controlled studies (RCTs) were located. The validity assessment revealed that the quality of the existing studies is very variable. This is the first systematic review in the area of imaging technologies for cervix brachytherapy. No RCTs have been located and it is possible that an RCT is not the optimal methodology to assess imaging technologies. However, in this area there is a need for more prospective studies and for studies that consider the expertise of the operators in their design. The studies found supported the use of three-dimensional imaging as opposed to the traditional two-dimensional imaging. However, apart from the effectiveness of visualising tumours and surrounding tissues, the utility of imaging technologies in clinical practice is determined by other contextual factors, such as their availability, accessibility and ease of use.