Variation of treatment planning parameters (D90 HR-CTV, D 2cc for OAR) for cervical cancer tandem ring brachytherapy in a multicentre setting: comparison of standard planning and 3D image guided optimisation based on a joint protocol for dose-volume constraints

Applicators used for vaginal high dose rate brachytherapy: Effect of type and shape on dose distribution and toxicity, a literature review

The aim of this article is to represent a literature review on the applicators used for vaginal high dose rate brachytherapy for patients with endometrial cancer. The different types and shapes of the clinically used applicator as well as the effects of their characteristics on dose distribution, target coverage and dose received by organs at risk are discussed in detail.

[Comparison between Stump Cylinder and custom mold, effect of the shape of the applicator on the dose distribution]

PURPOSE

The purpose of this study was to compare the efficacy of two applicators used in high dose rate vaginal brachytherapy. The first is the Stump Cylinder used in the "brachycenter" department at the Middle East Institute of Health in Lebanon and the second is the custom mold used in the radiotherapy department at Tenon Hospital in France.

MATERIALS AND METHOD

A comparison of the clinical target volume and the doses received by the rectum and bladder was performed in order to determine the best method of treatment and to optimize the dose distribution. 95 patients were treated in both departments.

RESULTS

The average values of the D95% dose received by the CTV were respectively 89.43% for the Stump Cylinder and 110.16% for the custom mold. The conformity index was 0.84 for the Stump Cylinder while it was 0.97 for the custom mold, which ensures a better dose distribution. For the rectum, the maximum dose D2cc taken by volume was 71.23% for the Stump Cylinder and 79.51% for the custom mold. The bladder was better protected with Stump Cylinder with a D2cc value of 65.81% against 94.88% for the custom mold.

CONCLUSION

The underdosing obtained using the Stump Cylinder was due to the shape of upper part of the cylinder which was not conform with the shape of the vaginal vault in women. A better protection of the organs at risk was observed with the Stump Cylinder since the dose taken by the rectum and bladder using a custom mold can reach the tolerance limits.

Interfraction Dose Variations in Organs at Risk during CT-Based High-Dose-Rate Brachytherapy in Locally Advanced Carcinoma Cervix: An Early Experience of a Tertiary Care Center

Purpose:

Dose received by organs at risk (OAR) in high-dose-rate (HDR) intracavitary brachytherapy (ICBT) for locally advanced cervical cancer impacts the late toxicity profile of the treatment. In the present study, we analyzed the inter-fraction variations of the minimum dose received by the most irradiated 2cc volumes (D_2cc) of the OARs in ICBT.

Methods and Materials:

This prospective study included 40 patients with cervical cancer stage FIGO IIB-IVA treated with HDR ICBT and concomitant chemoradiotherapy with Computerized tomography (CT)- based three-dimensional planning. In addition, for 20 (of the 40) patients, the first fraction plan was superimposed on the second fraction images for studying its dosimteric impact on the OAR. The D_2cc data for the OAR was statistically analyzed for interfraction variations with Chi-square test or Fisher exact test as applicable. Paired t-test was used to compare the difference in means for the D_2cc values between the three fractions.

Results:

The interfraction variations of the D_2cc values of the OAR were statistically insignificant having P = 0.41, 0.8, and 0.20 for bladder, rectum, and sigmoid, respectively. Further, in 6 out of 20 cases, wherein first fraction plan was superimposed on second fraction images, the OAR doses exceeded the prescribed tolerance limits.

Conclusion:

We did not find variations in the OAR doses when each fraction was planned and treated individually. However, we found that if a single plan is used to treat subsequent fractions, OAR doses may exceed tolerance in about 30% of the cases. We believe that a larger sample size with improved compliance of bladder and bowel protocols would be needed to arrive at definitive conclusions.

The value of systematic contouring of the bowel for treatment plan optimization in image-guided cervical cancer high-dose-rate brachytherapy

PURPOSE

To investigate the dose-volume histogram metrics and optimization results of the contoured bowel in cervical cancer brachytherapy.

METHODS AND MATERIALS

Treatment plans of cervical cancer patients treated with image-guided high dose rate were retrospectively analyzed with institutional review board approval. In addition to the clinical target volume, rectum, bladder, and sigmoid, the bowel was contoured at the time of planning (Group 1) or at the time of this analysis (Group 2).

RESULTS

Thirty-two patients treated with 145 insertions were included. Before optimization, mean ± 1 standard deviation overall bowel minimum dose to the most irradiated 2 cm³ volume of an organ (D_2cc) was 67.8 Gy_α/β3 ± 13.7 Gy_α/β3 (Group 1: 72.6 ± 13.2 Gy_α/β3; Group 2: 57.3 ± 8.0 Gy_α/β3). Before optimization, one patient in Group 1 presented a bowel D_2cc metric exceeding 100 Gy_α/β3. After optimization, bowel D_2cc mean ± 1 standard deviation was 59.4 ± 6.7 Gy_α/β3 (Group 1: 61.4 ± 6.0 Gy_α/β3, p < 0.001; Group 2: 55.2 ± 6.5 Gy_α/β3, p = 0.026).

CONCLUSIONS

Given the potentially high doses and the benefit of optimization in reducing dose to the organs at risk, we recommend consideration of systematic contouring of the bowel when bowel is present in the pelvis.

A comprehensive evaluation of adaptive daily planning for cervical cancer HDR brachytherapy

The purpose of this study was to evaluate adaptive daily planning for cervical cancer patients who underwent high‐dose‐rate intracavitary brachytherapy (HDR‐BT) using comprehensive interfractional organ motion measurements. This study included 22 cervical cancer patients who underwent 5 fractions of HDR‐BT. Regions of interest (ROIs) including high‐risk clinical tumor volume (HR‐CTV) and organs at risk (OARs) were manually contoured on daily CT images. All patients were clinically treated with adaptive daily plans (ADP), which involved ROI delineation and dose optimization at each treatment fraction. Single treatment plans (SP) were retrospectively generated by applying the first treatment fraction's dwell times adjusted for decay and dwell positions of the applicator to subsequent treatment fractions. Various existing similarity metrics were calculated for the ROIs to quantify interfractional organ variations. A novel similarity (JRARM) score was established, which combined both volumetric overlap metrics (DSC, JSC, and RVD) and distance metrics (ASD, MSD, and RMSD). Linear regression was performed to determine a relationship between interfractional organ variations of various similarity metrics and D2cc variations from both plans. Wilcoxon signed‐rank tests were used to assess ADP and SP by comparing EQD2D2cc(α/β=3) for OARs. For interfractional organ variations, the sigmoid demonstrated the greatest variations based on the JRARM, DSC, and RMSD metrics. Comparisons between paired ROIs showed differences in metrics at each treatment fraction. RVD, MSD, and RMSD were found to be significantly correlated to D2cc variations for bladder and sigmoid. The comparison between plans found ADP provided lower EQD2 D2cc of OARs than SP. Specifically, the sigmoid demonstrated statistically significant dose variations (p=0.015). Substantial interfractional organ motion occurs during HDR‐BT based on comprehensive measurements and may significantly affect D2cc of OARs. Adaptive daily planning provides improved dose sparing for OARs compared to single planning with the extent of sparing being different among OARs.

PACS number(s): 87.55.D, 87.55.de, 87.55.kh, 87.57.nj

Vaginal dose de-escalation in image guided adaptive brachytherapy for locally advanced cervical cancer

PURPOSE

Vaginal stenosis is a major problem following radiotherapy in cervical cancer. We investigated a new dose planning strategy for vaginal dose de-escalation (VDD).

MATERIALS AND METHODS

Fifty consecutive locally advanced cervical cancer patients without lower or middle vaginal involvement at diagnosis from 3 institutions were analysed. External beam radiotherapy was combined with MRI-guided brachytherapy. VDD was obtained by decreasing dwell times in ovoid/ring and increasing dwell times in tandem/needles. The aim was to maintain the target dose (D90 of HR-CTV⩾85Gy EQD2) while reducing the dose to the surface of the vagina to <140% of the physical fractional brachytherapy dose corresponding to a total EQD2 of 85Gy.

RESULTS

The mean vaginal loading (ovoid/ring) was reduced from 51% to 33% of the total loading with VDD, which significantly reduced the dose to the vaginal dose points (p<0.001) without compromising the target dose. The dose to the ICRU recto-vaginal point was reduced by a mean of 4±4Gy EQD2 (p<0.001), while doses to bladder and rectum (D_2cm³) were reduced by 2±2Gy and 3±2Gy, respectively (p<0.001).

CONCLUSIONS

VDD significantly reduces dose to the upper vagina which is expected to result in reduction of vaginal stenosis.

Clinical outcomes in cervical cancer patients treated by FDG-PET/CT-based 3-dimensional planning for the first brachytherapy session

The aim of the study was to evaluate the treatment outcomes in cervical cancer patients treated with 18F-fluorodeoxyglucose (FDG)-positron emission tomography (PET)/computed tomography (CT)-guided 3-dimensional brachytherapy (3D-BT) planning for the first brachytherapy session.We retrospectively analyzed 87 patients with cervical cancer who received definitive radiotherapy (RT). Primary tumor size was ≤4 cm in 22 patients (25.3%), >4 cm and ≤6 cm in 45 patients (51.7%), and >6 cm in 20 patients (23.0%). The median total dose of external beam RT was 50.4 (50.4-60.4) Gy. FDG-PET/CT-guided 3D-BT with an iridium-192 source was performed. The clinical target volume (CTV) for 3D-BT included the entire cervix and the abnormal FDG-uptake with a 1-cm expansion. A planned total dose was 24 Gy at 4 Gy per insertion 3 times per week using a tandem and 2 ovoids.The mean D95 and D90 for the CTV were 73.4 (±5.9) Gy and 77.9 (±6.9) Gy, respectively (EQD2, α/β=10). The D2cc for the rectum and bladder was 374 (±97.4) cGy and 394 (±107.6) cGy per fraction, respectively. The EQD2 (α/β=3) for the D2cc was 74.5 (±12.4) Gy for the rectum and 77.3 (±14.6) Gy for the bladder. The median follow-up period was 40 (8-61) months. The 3-year overall survival (OS), progression-free survival (PFS), and local control (LC) rates were 84.7%, 72.1%, and 89.2%, respectively. The 3-year LC rate was 100% for tumors ≤ 4 cm, 91.1% for tumors > 4 cm and ≤ 6 cm, and 70.5% for tumors > 6 cm (P = 0.014). Local failure developed in 9 patients. Three patients had local failures outside of the CTV. Grade 1, 2, and 3 rectal bleeding developed in 5, 4, and 2 patients, respectively. One patient experienced rectovaginal fistula.FDG-PET/CT-guided 3D-BT planning is a feasible approach, which showed favorable clinical outcomes.

Image-Guided High-Dose Rate Brachytherapy in Cervix Carcinoma Using Balloon Catheter and Belt Immobilization System

PURPOSE

The efficacy of image-guided high-dose rate brachytherapy for cervical cancer is limited by the ineffective rectal sparing devices available commercially and the potential applicator movement. We developed a novel device using a balloon catheter and a belt immobilization system, serving for rectal dose reduction and applicator immobilization purposes, respectively.

METHODS

The balloon catheter is constructed by gluing a short inflatable tube to a long regular open-end catheter. Contrast agent (10) cm³ is injected into the inflatable end, which is affixed to the tandem and ring applicator, to displace the posterior vaginal wall. The belt immobilization system consists of a specially designed bracket that can hold and fix itself to the applicator, a diaper-like Velcro fastener package used for connecting the patient's pelvis to the bracket, and a buckle that holds the fasteners to stabilize the whole system. The treatment data for 21 patients with cervical cancer using both balloon catheter and belt immobilization system were retrospectively analyzed. Computed tomography and magnetic resonance images, acquired about 30 minutes apart, were registered to evaluate the effectiveness of the immobilization system.

RESULTS

In comparison with a virtual rectal blade, the balloon decreased the rectal point dose by 34% ± 4.2% (from 276 ± 57 to 182 ± 38 cGy), corresponding to an extra sparing distance of 7.9 ± 1.1 mm. The maximum sparing distance variation per patient is 1.4 ± 0.6 mm, indicating the high interfractional reproducibility for rectum sparing. With the immobilization system, the mean translational and rotational displacements of the applicator set are <3 mm and <1.5°, respectively, in all directions.

CONCLUSIONS

The rectal balloon provides significant dose reduction to the rectum and it may potentially minimize patient discomfort. The immobilization system permits almost no movement of the applicator during treatment. This work has the potential to be promoted as a standardized solution for high-dose rate treatment of cervical cancer.

Review of advanced catheter technologies in radiation oncology brachytherapy procedures

The development of new catheter and applicator technologies in recent years has significantly improved treatment accuracy, efficiency, and outcomes in brachytherapy. In this paper, we review these advances, focusing on the performance of catheter imaging and reconstruction techniques in brachytherapy procedures using magnetic resonance images and electromagnetic tracking. The accuracy of catheter reconstruction, imaging artifacts, and other notable properties of plastic and titanium applicators in gynecologic treatments are reviewed. The accuracy, noise performance, and limitations of electromagnetic tracking for catheter reconstruction are discussed. Several newly developed applicators for accelerated partial breast irradiation and gynecologic treatments are also reviewed. New hypofractionated high dose rate treatment schemes in prostate cancer and accelerated partial breast irradiation are presented.

Image-guided radiotherapy and -brachytherapy for cervical cancer

Conventional radiotherapy for cervical cancer relies on clinical examination, 3-dimensional conformal radiotherapy (3D-CRT), and 2-dimensional intracavitary brachytherapy. Excellent local control and survival have been obtained for small early stage cervical cancer with definitive radiotherapy. For bulky and locally advanced disease, the addition of chemotherapy has improved the prognosis but toxicity remains significant. New imaging technology such as positron-emission tomography and magnetic resonance imaging has improved tumor delineation for radiotherapy planning. Image-guided radiotherapy (IGRT) may decrease treatment toxicity of whole pelvic radiation because of its potential for bone marrow, bowel, and bladder sparring. Tumor shrinkage during whole pelvic IGRT may optimize image-guided brachytherapy (IGBT), allowing for better local control and reduced toxicity for patients with cervical cancer. IGRT and IGBT should be integrated in future prospective studies for cervical cancer.

Inter-application displacement of brachytherapy dose received by the bladder and rectum of the patients with inoperable cervical cancer

BACKGROUND

The aim of the study was to examine on the CT basis the inter-application displacement of the positions D0.1cc, D1cc and D2cc of the brachytherapy dose applied to the bladder and rectum of the patients with inoperable cervical cancer.

PATIENTS AND METHODS

This prospective study included 30 patients with cervical cancer who were treated by concomitant chemo-radiotherapy. HDR intracavitary brachytherapy was made by the applicators type Fletcher tandem and ovoids. For each brachytherapy application the position D0.1cc was determined of the bladder and rectum that receive a brachytherapty dose. Then, based on the X, Y, and Z axis displacement, inter-application mean X, Y, and Z axis displacements were calculated as well as their displacement vectors (R). It has been analyzed whether there is statistically significant difference in inter-application displacement of the position of the brachytherapy dose D0.1cc, D1cc and D2cc of the bladder and rectum. The ANOVA test and post-hoc analysis by Tukey method were used for testing statistical importance of differences among the groups analyzed. The difference among the groups analyzed was considered significant if p < 0.05.

RESULTS

There are significant inter-application displacements of the position of the brachytherapy dose D0,1cc, D1cc and D2cc of the bladder and rectum.

CONCLUSIONS

When we calculate the cumulative brachytherapy dose by summing up D0,1cc, D1cc and D2cc of the organs at risk for all the applications, we must bear in mind their inter-application displacement, and the fact that it is less likely that the worst scenario would indeed happen.

Does inadequate Point-A dose warrant treatment plan modifications in CT-image-based cervix high dose-rate brachytherapy planning? A dosimetric perspective

Background and purpose

To investigate whether inadequate dose to Point-A necessitates treatment plan changes in a time of computed tomography (CT)-image-guided brachytherapy treatment planning for cervix cancer.

Materials and methods

A total of 125 tandem and ovoid insertions from 25 cervix patients treated were reviewed. CT-image-based treatment planning was carried out for each insertion. Point-A is identified and the dose documented; however, dose optimisation in each plan was based on covering target while limiting critical organ doses (PlanTarget). No attempts were made to equate prescription and Point-A dose. For each insertion, a second hypothetical treatment plan was generated by prescribing dose to Point-A (PlanPoint-A). Plans were inter-compared using dose–volume histogram analyses.

Results

A total of 250 treatment plans were analysed. For the study population, the median cumulative dose at Point-A was 80 Gy (range 70–95) for PlanTarget compared with 84·25 Gy for PlanPoint-A. Bladder and rectal doses were higher for PlanPoint-A compared with PlanTarget (p < 0·0001). Target D90 did not correlate with Point-A dose (p = 0·60).

Conclusions

Depending on applicator geometry, tumour size and patient anatomy, Point-A dose may vary in magnitude compared with prescription dose. Treatment plan modifications purely based on inadequate Point-A dose are unnecessary, as these may result in higher organ-at-risk doses and not necessarily improve target coverage.

Equivalence of Gyn GEC-ESTRO guidelines for image guided cervical brachytherapy with EUD-based dose prescription

Background

To establish a generalized equivalent uniform dose (gEUD) -based prescription method for Image Guided Brachytherapy (IGBT) that reproduces the Gyn GEC-ESTRO WG (GGE) prescription for cervix carcinoma patients on CT images with limited soft tissue resolution.

Methods

The equivalence of two IGBT planning approaches was investigated in 20 patients who received external beam radiotherapy (EBT) and 5 concomitant high dose rate IGBT treatments. The GGE planning strategy based on dose to the most exposed 2 cm³ (D2cc) was used to derive criteria for the gEUD-based planning of the bladder and rectum. The safety of gEUD constraints in terms of GGE criteria was tested by maximizing dose to the gEUD constraints for individual fractions.

Results

The gEUD constraints of 3.55 Gy for the rectum and 5.19 Gy for the bladder were derived. Rectum and bladder gEUD-maximized plans resulted in D2cc averages very similar to the initial GGE criteria. Average D2ccs and EUDs from the full treatment course were comparable for the two techniques within both sets of normal tissue constraints. The same was found for the tumor doses.

Conclusions

The derived gEUD criteria for normal organs result in GGE-equivalent IGBT treatment plans. The gEUD-based planning considers the entire dose distribution of organs in contrast to a single dose-volume-histogram point.

Pulsed-dose-rate brachytherapy for uterine cervix carcinoma: 10 years of experience with 226 patients at a single institution

PURPOSE

To analyze the long-term results of pulsed-dose-rate (PDR) brachytherapy (BT) in cervical carcinoma patients treated at a single institution.

METHODS AND MATERIALS

All patients with histopathologically proven Stages IB-IVA cervical carcinoma, treated at our institution with PDR intracavitary BT between April 1996 and November 2007, were included in this retrospective analysis. All patients underwent primary pelvic radiotherapy (45 Gy) with concomitant chemotherapy from 1999 and PDR intracavitary BT (16 Gy to the clinical target volume), followed by hysterectomy in 124 patients.

RESULTS

Two hundred twenty-six patients received radiochemotherapy and BT. With a median followup of 81.7 months, the 5-year overall survival, disease-free survival, and local control (LC) were 67%, 65%, and 80%, respectively; seventy-seven relapses were observed including 38 local recurrences. Multivariate analysis showed earlier FIGO (International Federation of Gynecology and Obstetrics) stage and absence of nodal involvement to be associated with better overall and disease-free survivals. Use of three-dimensional image-guided BT planning and absence of nodal involvement were associated with better LC in the multivariate analysis. Late Grade ≥3 toxicity was experienced by 22 patients (9.7%), consisting of gastrointestinal toxicity for 6 patients, urinary tract for 10 patients, lymphatics for 3 patients, and vaginal toxicity for 3 patients.

CONCLUSIONS

This study demonstrates excellent LC rates with few late side effects with PDR BT for cervix carcinoma, similar to those reported in the literature with historical standard low-dose-rate BT.

Evaluation of microscopic tumor extension in early-stage cervical cancer: quantifying subclinical uncertainties by pathological and magnetic resonance imaging findings

We performed a detailed analysis of hysterectomy specimens of uterine cervical cancer to determine the appropriate length of uterine body to include within the clinical target volume. Between 2008 and 2011, 54 patients with uterine cervical carcinoma underwent hysterectomy. Those with quality pre-operative magnetic resonance imaging (MRI) data were included for analysis. Tumor sizes measured by MRI and microscopy were compared with regard to brachytherapy-oriented parameters. Detailed descriptive analysis focusing on the extent of tumor involvement was also performed. A total of 31 specimens were analyzed. The median maximal tumor length measured by MRI was slightly shorter than microscopic length (19 vs. 24 mm, respectively), while the maximal radius was almost identical. No tumors with a maximal size <2 cm by MRI (n = 6) extended to the uterine body ≥ 1/3. The majority of maximal tumor length underestimation on MRI was within 1 cm. Precise tumor delineation can be made by MRI. For patients with tumors <2 cm on MRI, treating the entire uterine body length may not be necessary. A 1-cm margin around an MRI-based gross tumor seems to be adequate to cover the actual tumor involvement.

A review of recent developments in image-guided radiation therapy in cervix cancer

Brachytherapy is an essential part of radiotherapy treatment for cervical cancer. Over the decades, it has evolved from manual loading of radium and caesium to remote after-loaders and from low-dose and medium-dose rates to high-dose rates. Over the past 10 years, 3D image-based Brachytherapy has evolved and established itself as the gold standard, improving local control and overall survival, and significantly reducing toxicity. In this article, we review some of the available literature on gynaecologic brachytherapy, more specifically on topics such as dose rates, high-dose-rate/pulsed-dose-rate (HDR/PDR) brachytherapy and image-based brachytherapy (IBBT), and present some of the evidence that establishes IBBT.

Single line source with and without vaginal loading and the impact on target coverage and organ at risk doses for cervix cancer Stages IB, II, and IIIB: treatment planning simulation in patients treated with MRI-guided adaptive brachytherapy in a multicentre study (EMBRACE)

PURPOSE

Three-dimensional evaluation and comparison of target and organs at risk (OARs) doses from two traditional standard source loading patterns in the frame of MRI-guided cervical cancer brachytherapy for various clinical scenarios based on patient data collected in a multicenter trial setting.

METHODS AND MATERIALS

Two nonoptimized three-dimensional MRI-based treatment plans, Plan 1 (tandem and vaginal loading) and Plan 2 (tandem loading only), were generated for 134 patients from seven centers participating in the EMBRACE study. Both plans were normalized to point A (Pt. A). Target and OAR doses were evaluated in terms of minimum dose to 90% of the high-risk clinical target volume (HRCTV D90) grouped by tumor stage and minimum dose to the most exposed 2cm³ of the OARs volume.

RESULTS

An HRCTV D90 ≥ Pt. A was achieved in 82% and 44% of the patients with Plans 1 and 2, respectively. Median HRCTV D90 with Plans 1 and 2 was 120% and 90% of Pt. A dose, respectively. Both plans had optimal dose coverage in 88% of Stage IB tumors; however, the tandem-only plan resulted in about 50% of dose reduction to the vagina and rectum. For Stages IIB and IIIB, Plan 1 had on average 35% better target coverage but with significant doses to OARs.

CONCLUSIONS

Standard tandem loading alone results in good target coverage in most Stage IB tumors without violating OAR dose constraints. For Stage IIB tumors, standard vaginal loading improves the therapeutic window, however needs optimization to fulfill the dose prescription for target and OAR. In Stage IIIB, even optimized vaginal loading often does not fulfill the needs for dose prescription. The significant dose variation across various clinical scenarios for both target and OARs indicates the need for image-guided brachytherapy for optimal dose adaptation both for limited and advanced diseases.

Adaptive image guided brachytherapy for cervical cancer: a combined MRI-/CT-planning technique with MRI only at first fraction

PURPOSE

To investigate and test the feasibility of adaptive 3D image based BT planning for cervix cancer patients in settings with limited access to MRI, using a combination of MRI for the first BT fraction and planning of subsequent fractions on CT.

MATERIAL AND METHODS

For 20 patients treated with EBRT and HDR BT with tandem/ring applicators two sets of treatment plans were compared. Scenario one is based on the "gold standard" with individual MRI-based treatment plans (applicator reconstruction, target contouring and dose optimization) for two BT applications with two fractions each. Scenario two is based on one initial MRI acquisition with an applicator in place for the planning of the two fractions of the first BT application and reuse of the target contour delineated on MRI for subsequent planning of the second application on CT. Transfer of the target from MRI of the first application to the CT of the second one was accomplished by use of an automatic applicator-based image registration procedure. Individual dose optimization of the second BT application was based on the transferred MRI target volume and OAR structures delineated on CT. DVH parameters were calculated for transferred target structures (virtual dose from MRI/CT plan) and CT-based OAR. The quality of the MRI/CT combination method was investigated by evaluating the CT-based dose distributions on MRI-based target and OAR contours of the same application (real dose from MRI/CT plan).

RESULTS

The mean difference between the MRI based target volumes (HR CTVMRI2) and the structures transferred from MRI to CT (HR CTVCT2) was -1.7±6.6 cm(3) (-2.9±20.4%) with a median of -0.7 cm(3). The mean difference between the virtual and the real total D90, based on the MRI/CT combination technique was -1.5±4.3 Gy EQD2. This indicates a small systematic underestimation of the real D90.

CONCLUSIONS

A combination of MRI for first fraction and subsequent CT based planning is feasible and easy when automatic applicator-based image registration and target transfer are technically available. The results show striking similarity to fully MRI-based planning in cases of small tumours and intracavitary applications, both in terms of HR CTV coverage and respecting of OAR dose limits. For larger tumours and complex applications, as well as situations with unfavourable OAR topography, especially for the sigmoid, MRI based adaptive BT planning remains the superior method.

Residual rotational set-up errors after daily cone-beam CT image guided radiotherapy of locally advanced cervical cancer

PURPOSE

Due to the often quite extended treatment fields in cervical cancer radiotherapy, uncorrected rotational set-up errors result in a potential risk of target miss. This study reports on the residual rotational set-up error after using daily cone beam computed tomography (CBCT) to position cervical cancer patients for radiotherapy treatment.

METHODS AND MATERIALS

Twenty-five patients with locally advanced cervical cancer had daily CBCT scans (650 CBCTs in total) prior to treatment delivery. We retrospectively analyzed the translational shifts made in the clinic prior to each treatment fraction as well as the residual rotational errors remaining after translational correction.

RESULTS

The CBCT-guided couch movement resulted in a mean translational 3D vector correction of 7.4 mm. Residual rotational error resulted in a target shift exceeding 5 mm in 57 of the 650 treatment fractions. Three patients alone accounted for 30 of these fractions. Nine patients had no shifts exceeding 5 mm and 13 patients had 5 or less treatment fractions with such shifts.

CONCLUSION

Twenty-two of the 25 patients have none or few treatment fractions with target shifts larger than 5mm due to residual rotational error. However, three patients display a significant number of shifts suggesting a more systematic set-up error.

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.

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.

Image guided, adaptive, accelerated, high dose brachytherapy as model for advanced small volume radiotherapy

Brachytherapy has consistently provided a very conformal radiation therapy modality. Over the last two decades this has been associated with significant improvements in imaging for brachytherapy applications (prostate, gynecology), resulting in many positive advances in treatment planning, application techniques and clinical outcome. This is emphasized by the increased use of brachytherapy in Europe with gynecology as continuous basis and prostate and breast as more recently growing fields. Image guidance enables exact knowledge of the applicator together with improved visualization of tumor and target volumes as well as of organs at risk providing the basis for very individualized 3D and 4D treatment planning. In this commentary the most important recent developments in prostate, gynecological and breast brachytherapy are reviewed, with a focus on European recent and current research aiming at the definition of areas for important future research. Moreover the positive impact of GEC-ESTRO recommendations and the highlights of brachytherapy physics are discussed what altogether presents a full overview of modern image guided brachytherapy. An overview is finally provided on past and current international brachytherapy publications focusing on "Radiotherapy and Oncology". These data show tremendous increase in almost all research areas over the last three decades strongly influenced recently by translational research in regard to imaging and technology. In order to provide high level clinical evidence for future brachytherapy practice the strong need for comprehensive prospective clinical research addressing brachytherapy issues is high-lighted.

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.

Local recurrences in cervical cancer patients in the setting of image-guided brachytherapy: a comparison of spatial dose distribution within a matched-pair analysis

Purpose

It has been shown that a cumulative dose of ⩾87 Gy (EQD2) of external beam radiotherapy (EBRT) and image guided adaptive brachytherapy (IGABT) to the high risk clinical target volume (HR CTV) confer a local control rate >95% in locally advanced cervical cancer. This study examines the dose distribution within the HR CTV and intermediate (IR) CTV in patients with cervical cancer treated with definitive EBRT +/− concomitant chemotherapy and MRI-based IGABT between patients with local recurrence (LR) and patients in continuous complete local remission (CCLR).

Material and methods

From 1998 to 2010, 265 patients were treated with definitive EBRT +/− concomitant chemotherapy and IGABT. Twenty-four LRs were documented. For the statistical analysis all patients with LR were matched to patients in CCLR from our database according to the following criteria: FIGO stage, histology, lymph node status, tumour size and chemotherapy.

DVH parameters (D50, D90, D98, D100) were reported for HR CTV and IR CTV. In order to report the minimum dose in the region where the recurrence occurred, the HR CTV/IR CTV were divided into four quadrants on transversal planes. The minimum dose at the HR CTV/IR CTV contour was measured (within the corresponding quadrant closest to the LR) in the treatment planning system. A mean minimum point dose (MPD) was calculated by averaging these measurements on four consecutive slices at the level of the recurrence for each of the 4 brachytherapy fractions. EQD2 doses were calculated by summation of all BT and external beam therapy fractions.

For each matched patient in the control group the measurements were performed on the same quadrant and at the same level.

Results

Sufficient image data were available for 21 LRs. Eight central failures and 13 non-central failures were observed. The mean D90 and D100 for HR CTV were 77 Gy and 61 Gy for patients with LR and 95 Gy and 71 Gy for patients in CCLR, respectively (p < 0.01). The MPD for HR CTV was 72 Gy for patients in the LR arm and 99 Gy for patients in the CCLR arm (p < 0.01). In the LR arm seven patients had a D90 for HR CTV ⩾87 Gy, however, in only three patients the MPD was ⩾87 Gy.

Conclusion

This study demonstrated significant differences in local outcome according to the delivered dose. In 85% of the LRs systematic low dose regions with less than 87 Gy were found at HR CTV contour. Systematic low dose regions leading to local recurrence could be detected even if a D90 HR CTV ⩾87 Gy was applied. In addition to DVH parameters, inspection of the spatial dose distribution remains a key point in dose prescription.

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.

Patterns of care study for brachytherapy: results of the questionnaire for the years 2002 and 2007 in The Netherlands

Purpose

The goal of the ESTRO Patterns of Care study for Brachytherapy in Europe (PCBE) 2002 was to develop an aid to analyse brachytherapy practices. A 2^nd version of the PCB questionnaire was created for 2007. Data over 2007 were collected at the radiotherapy institutions in The Netherlands and compared with those from 2002. The aim of this study is to describe national brachytherapy practices, to demonstrate trends, and to provide data for rational health care planning.

Material and methods

Data were collected using a web-based questionnaire. For each centre, a local coordinator, responsible for coordinating the questionnaires and support of the further analysis was assigned. Data from the national cancer incidence registry was used for comparison with the data from the 21 Dutch departments.

Results

There was a decrease in low-dose rate equipment in parallel to an increase in both pulsed-dose rate and high-dose rate equipment. The use of 3D CT and MR based imaging techniques showed a slow rise. The most common clinical procedures were for prostate, gynaecological, and oesophageal tumours. A large increase (146%) in permanent implant prostate applications using 125I seeds was observed. The numbers of oesophageal and gynaecological treatments remained stable. There is concern on the low numbers of cases treated in some institutions for a few complex treatment sites. For head and neck, anal canal, paediatrics, bladder and eye interventions it ranged from 3-20 patients per year per institution.

Conclusions

The increase in number of patient treated with brachytherapy is in accordance with the increases in cancer incidence. The percentage of all radiotherapy patients treated with brachytherapy (approximately 5%) remained stable. The survey identified certain trends in resources and techniques, as well as areas of expected improvement and possible gain in clinical outcome. Data reported from this survey can be used for further planning of resources, facilities and concentration of a low-volume specialised and complex treatments.

From point A to the sculpted pear: MR image guidance significantly improves tumour dose and sparing of organs at risk in brachytherapy of cervical cancer

BACKGROUND AND PURPOSE

Brachytherapy in locally advanced cervical cancer is still widely based on 2D standard dose planning, although 3D image guidance is available. The purpose of this study was to compare point doses to 3D dose volume parameters for tumour and organs at risk (OARs), and to evaluate the improvement of dose parameters with MR image guided adaptive brachytherapy (IGABT).

MATERIAL AND METHODS

MRI-based IGABT was performed in 72 consecutive patients. HR-CTV, IR-CTV, bladder, rectum and sigmoid were contoured according to GEC-ESTRO recommendations. BT standard dose planning was compared to MRI-based dose optimisation.

RESULTS

HR-CTV dose (D90) was highly variable in standard plans with point A dose prescription. In small tumours (<31 cc) HR-CTV was well covered by standard plans in 94% of patients, while OAR constraints were exceeded in 72% of patients. Optimisation decreased violation of OAR constraints to only 6% of patients while maintaining excellent target coverage. In large tumours (>31 cc) the dose optimisation improved the HR-CTV D90 by a mean of 7 Gy resulting in full coverage in 72% of patients as compared to 25% for standard plans, even while reducing violation of OAR constraints.

CONCLUSION

Point A dose is a poor surrogate of HR-CTV dose, and the use of 3D image-based dose planning is encouraged. MRI-based IGABT significantly improves target coverage and OAR dose.