Variability of target volume delineation in cervical esophageal cancer

Interstitial-guided automatic clinical tumor volume segmentation network for cervical cancer brachytherapy

Automatic clinical tumor volume (CTV) delineation is pivotal to improving outcomes for interstitial brachytherapy cervical cancer. However, the prominent differences in gray values due to the interstitial needles bring great challenges on deep learning-based segmentation model. In this study, we proposed a novel interstitial-guided segmentation network termed advance reverse guided network (ARGNet) for cervical tumor segmentation with interstitial brachytherapy. Firstly, the location information of interstitial needles was integrated into the deep learning framework via multi-task by a cross-stitch way to share encoder feature learning. Secondly, a spatial reverse attention mechanism is introduced to mitigate the distraction characteristic of needles on tumor segmentation. Furthermore, an uncertainty area module is embedded between the skip connections and the encoder of the tumor segmentation task, which is to enhance the model's capability in discerning ambiguous boundaries between the tumor and the surrounding tissue. Comprehensive experiments were conducted retrospectively on 191 CT scans under multi-course interstitial brachytherapy. The experiment results demonstrated that the characteristics of interstitial needles play a role in enhancing the segmentation, achieving the state-of-the-art performance, which is anticipated to be beneficial in radiotherapy planning.

[Usefulness of Metal Artifact-reduced Reconstruction for Image-guided Brachytherapy for Cervical Cancer]

PURPOSE

To evaluate the usefulness of single-energy metal artifact reduction (SEMAR) for target delineation in brachytherapy for cervical cancer patients with metal hip implants.

MATERIAL AND METHODS

A series of four definitive brachytherapy sessions in the same patient was analyzed. At each brachytherapy session, the identical set of computed tomography images was subjected with or without SEMAR treatment. For both SEMAR-treated and -untreated sets, five radiation oncologists delineated the high-risk clinical target volume (HR-CTV), bladder, and rectum, for which the volume, Dice coefficient, and the dose volume parameters were compared between SEMAR-treated and -untreated datasets.

RESULTS

The bladder volume was significantly greater in the SEMAR-treated datasets compared with the SEMAR-untreated datasets. Importantly, for the bladder, Dice coefficient among five radiation oncologists was significantly higher for the SEMAR-treated datasets compared with the SEMAR-untreated datasets. These effects of SEMAR treatment were not evident for HR-CTV and the rectum.

CONCLUSIONS

These data indicate that SEMAR treatment contributes to improve delineation of the bladder in brachytherapy for cervical cancer patients with metal hip implants.

Impact of Interobserver Variability in Manual Segmentation of Non-Small Cell Lung Cancer (NSCLC) Applying Low-Rank Radiomic Representation on Computed Tomography

Simple Summary

Discovery of predictive and prognostic radiomic features in cancer is currently of great interest to the radiologic and oncologic community. Tumor phenotypic and prognostic information can be obtained by extracting features on tumor segmentations, and it is typically imaging analysts, physician trainees, and attending physicians who provide these labeled datasets for analysis. The potential impact of level and type of specialty training on interobserver variability in manual segmentation of NSCLC was examined. Although there was some variability in segmentation between readers, the subsequently extracted radiomic features were overall well correlated. High fidelity radiomic feature extraction relies on accurate feature extraction from imaging that produce robust prognostic and predictive radiomic NSCLC biomarkers. This study concludes that this goal can be obtained using segmenters of different levels of training and clinical experience.

Abstract

This study tackles interobserver variability with respect to specialty training in manual segmentation of non-small cell lung cancer (NSCLC). Four readers included for segmentation are: a data scientist (BY), a medical student (LS), a radiology trainee (MH), and a specialty-trained radiologist (SK) for a total of 293 patients from two publicly available databases. Sørensen–Dice (SD) coefficients and low rank Pearson correlation coefficients (CC) of 429 radiomics were calculated to assess interobserver variability. Cox proportional hazard (CPH) models and Kaplan-Meier (KM) curves of overall survival (OS) prediction for each dataset were also generated. SD and CC for segmentations demonstrated high similarities, yielding, SD: 0.79 and CC: 0.92 (BY-SK), SD: 0.81 and CC: 0.83 (LS-SK), and SD: 0.84 and CC: 0.91 (MH-SK) in average for both databases, respectively. OS through the maximal CPH model for the two datasets yielded c-statistics of 0.7 (95% CI) and 0.69 (95% CI), while adding radiomic and clinical variables (sex, stage/morphological status, and histology) together. KM curves also showed significant discrimination between high- and low-risk patients (p-value < 0.005). This supports that readers’ level of training and clinical experience may not significantly influence the ability to extract accurate radiomic features for NSCLC on CT. This potentially allows flexibility in the training required to produce robust prognostic imaging biomarkers for potential clinical translation.

ESTRO ACROP guidelines for the delineation of lymph nodal areas in upper gastrointestinal malignancies

The European SocieTy for Radiation and Oncology -Advisory Committee on Radiation Oncology Practice (ESTRO-ACROP) endorsed a project to provide guidelines (GL) for the identification and delineation of clinically negative lymph-nodal stations (LNs) involved in upper gastrointestinal clinical scenarios. The presented GL is focused on preoperative (or definitive) setting. The project aim is to improve the consistency of clinical target volume (CTV) delineation by providing: a description of the anatomical boundaries of the LNs; a radiological computed tomography-based atlas depicting the LNs areas; a free, web-based, interactive example case for independent training of radiation oncologists on LNs delineation according to the presented GL, by both qualitative and quantitative analysis (through the FALCON EduCase platform). This project was carried out with the intention to facilitate and improve uniformity of future upper gastrointestinal guidelines on nodal CTV delineation. We report methodology and results from the collaboration of a working group panel selected by the ESTRO-ACROP.

Interobserver variability in target volume delineation in definitive radiotherapy for thoracic esophageal cancer: a multi-center study from China

Purpose

To investigate the interobserver variability (IOV) in target volume delineation of definitive radiotherapy for thoracic esophageal cancer (TEC) among cancer centers in China, and ultimately improve contouring consistency as much as possible to lay the foundation for multi-center prospective studies.

Methods

Sixteen cancer centers throughout China participated in this study. In Phase 1, three suitable cases with upper, middle, and lower TEC were chosen, and participants were asked to contour a group of gross tumor volume (GTV-T), nodal gross tumor volume (GTV-N) and clinical target volume (CTV) for each case based on their routine experience. In Phase 2, the same clinicians were instructed to follow a contouring protocol to re-contour another group of target volume. The variation of the target volume was analyzed and quantified using dice similarity coefficient (DSC).

Results

Sixteen clinicians provided routine volumes, whereas ten provided both routine and protocol volumes for each case. The IOV of routine GTV-N was the most striking in all cases, with the smallest DSC of 0.37 (95% CI 0.32–0.42), followed by CTV, whereas GTV-T showed high consistency. After following the protocol, the smallest DSC of GTV-N was improved to 0.64 (95% CI 0.45–0.83, P = 0.005) but the DSC of GTV-T and CTV remained constant in most cases.

Conclusion

Variability in target volume delineation was observed, but it could be significantly reduced and controlled using mandatory interventions.

Supplementary information

Supplementary information accompanies this paper at 10.1186/s13014-020-01691-4.

Three-dimensional (3D) magnetic resonance volume assessment and loco-regional failure in anal cancer: early evaluation case-control study

Background

The primary aim was to test the hypothesis that deriving pre-treatment 3D magnetic resonance tumour volume (mrTV) quantification improves performance characteristics for the prediction of loco-regional failure compared with standard maximal tumour diameter (1D) assessment in patients with squamous cell carcinoma of the anus undergoing chemoradiotherapy.

Methods

We performed an early evaluation case-control study at two UK centres (2007–2014) in 39 patients with loco-regional failure (cases), and 41 patients disease-free at 3 years (controls). mrTV was determined using the summation of areas method (Vol_sum). Reproducibility was assessed using intraclass concordance correlation (ICC) and Bland-Altman limits of agreements. We derived receiver operating curves using logistic regression models and expressed accuracy as area under the curve (ROC_AUC).

Results

The median time per patient for Vol_sum quantification was 7.00 (inter-quartile range, IQR: 0.57–12.48) minutes. Intra and inter-observer reproducibilities were generally good (ICCs from 0.79 to 0.89) but with wide limits of agreement (intra-observer: − 28 to 31%; inter-observer: − 28 to 46%). Median mrTVs were greater for cases (32.6 IQR: 21.5–53.1 cm³) than controls (9.9 IQR: 5.7–18.1 cm³, p < 0.0001). The ROC_AUC for mrT-size predicting loco-regional failure was 0.74 (95% CI: 0.63–0.85) improving to 0.82 (95% CI: 0.72–0.92) when replaced with mrTV (test for ROC differences, p = 0.024).

Conclusion

Preliminary results suggest that the replacement of mrTV for mrT-size improves prediction of loco-regional failure after chemoradiotherapy for squamous cell carcinoma of the anus. However, mrTV calculation is time consuming and variation in its reproducibility are drawbacks with the current technology.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-020-07613-7.

DeepTarget: Gross tumor and clinical target volume segmentation in esophageal cancer radiotherapy

Gross tumor volume (GTV) and clinical target volume (CTV) delineation are two critical steps in the cancer radiotherapy planning. GTV defines the primary treatment area of the gross tumor, while CTV outlines the sub-clinical malignant disease. Automatic GTV and CTV segmentation are both challenging for distinct reasons: GTV segmentation relies on the radiotherapy computed tomography (RTCT) image appearance, which suffers from poor contrast with the surrounding tissues, while CTV delineation relies on a mixture of predefined and judgement-based margins. High intra- and inter-user variability makes this a particularly difficult task. We develop tailored methods solving each task in the esophageal cancer radiotherapy, together leading to a comprehensive solution for the target contouring task. Specifically, we integrate the RTCT and positron emission tomography (PET) modalities together into a two-stream chained deep fusion framework taking advantage of both modalities to facilitate more accurate GTV segmentation. For CTV segmentation, since it is highly context-dependent-it must encompass the GTV and involved lymph nodes while also avoiding excessive exposure to the organs at risk-we formulate it as a deep contextual appearance-based problem using encoded spatial distances of these anatomical structures. This better emulates the margin- and appearance-based CTV delineation performed by oncologists. Adding to our contributions, for the GTV segmentation we propose a simple yet effective progressive semantically-nested network (PSNN) backbone that outperforms more complicated models. Our work is the first to provide a comprehensive solution for the esophageal GTV and CTV segmentation in radiotherapy planning. Extensive 4-fold cross-validation on 148 esophageal cancer patients, the largest analysis to date, was carried out for both tasks. The results demonstrate that our GTV and CTV segmentation approaches significantly improve the performance over previous state-of-the-art works, e.g., by 8.7% increases in Dice score (DSC) and 32.9mm reduction in Hausdorff distance (HD) for GTV segmentation, and by 3.4% increases in DSC and 29.4mm reduction in HD for CTV segmentation.

Contribution of Magnetic Resonance Imaging in Determining Lumpectomy Cavity in Breast Radiotherapy

BACKGROUND

Accurate localization of the lumpectomy cavity is important for breast cancer radiotherapy after breast-conserving surgery (BCS), but the LC localization based on CT is often difficult to delineate accurately. The study aimed to compare CT-defined LC planning to MRI-defined findings in the supine position for higher soft-tissue resolution of MRI.

METHODS

Fifty-nine breast cancer patients underwent radiotherapy CT planning in supine position followed by MR imaging on the same day. LC was contoured by the radiologist and radiation oncologist together by CT and MRI separately. T2 weighted MR images and tomography findings were combined and the LC volume, mean diameter and the longest axis length were measured after contouring. Subsequently, patients were divided into two groups according to seroma in LC and the above-mentioned parameters were compared.

RESULTS

We did not find any statistically significant difference in the LC volume, mean diameter and length at the longest axis between CT and MRI but based on the presence or absence of seroma, statistically significant differences were found in the LC volumes and the length at the longest axis of LC volumes.

CONCLUSION

We believe that the supine MRI in the same position with CT will be more effective for radiotherapy planning, particularly in patients without a seroma in the surgical cavity.

The Impact of Positron Emission Tomography/Computed Tomography Addition to Contrast-Enhanced Computed Tomography Findings during Radiation Treatment Planning of Locally Advanced Carcinoma Esophagus

Introduction:

Does metabolic imaging help in better definition of target during radiation treatment planning by bringing about changes in dimensions of the primary tumor in terms of diameter, length, and picking up new skip lesions or nodal stations which in turn prevents geographic misses by including more ¹⁸F-fluorodeoxyglucose avid regions not visible on conventional imaging?

Materials and Methods:

We compared the length and radial dimensions of the primary tumor as well as changes brought about due to addition of new nodal stations, involved structures, and skip lesions in 50 patients of carcinoma esophagus treated between 2011 and 2013, as seen on contrast-enhanced computed tomography (CT) thorax and positron emission tomography (PET)/CT and drew conclusions regarding the technical changes brought about in treatment planning by the additional input of PET/CT.

Results and Conclusions:

PET-CT tremendously changes treatment plans by expanding the gross tumor volume and including regions which might otherwise have been missed on purely CT-based plans. Of the 50 patients, it changed the contouring and treatment planning of 35 patients and did not impact the remaining 15. Whether this translates into better long-term controls requires further validation by randomized controlled trials, which was not our present objective.

Provision of Organ at Risk Contouring Guidance in UK Radiotherapy Clinical Trials

AIMS

Accurate delineation of organs at risk (OAR) is vital to the radiotherapy planning process. Inaccuracies in OAR delineation arising from imprecise anatomical definitions may affect plan optimisation and risk inappropriate dose delivery to normal tissues. The aim of this study was to review the provision of OAR contouring guidance in National Institute of Health Research Clinical Research Network (NIHR CRN) portfolio clinical trials.

MATERIALS AND METHODS

The National Radiotherapy Quality Trials Assurance (RTTQA) Group carried out a two-round Delphi assessment to determine which OAR descriptions provided optimal guidance.

RESULTS

Eighty-four clinical trials involving radiotherapy quality assurance were identified as either in recruitment or in setup within the NIHR CRN portfolio. Fifty-nine trials mandated OAR contouring. In total there were 412 OAR; 171 were uniquely named; 159 OAR had more than one name associated with a single structure, with the greatest nomenclature variation seen for the femoral head ± neck, the parotid gland, and bowel. The two-round Delphi assessment determined 42 OAR descriptions as providing optimal contouring guidance.

CONCLUSIONS

This study identified the need for OAR nomenclature and contouring guidance consistency across clinical trials. In response to this study and in conjunction with the Global Quality Assurance of Radiation Therapy Clinical Trials Harmonisation Group, the RTTQA Group is in collaboration with international partners to provide consensus recommendations for OAR delineation in clinical trials.

Reduced inter-observer and intra-observer delineation variation in esophageal cancer radiotherapy by use of fiducial markers

Objective: Delineation variation of esophageal tumors remains a large source of geometric uncertainty. In the present study, we investigated the inter- and intra-observer variation in esophageal gross tumor volume (GTV) delineation and the impact of endoscopically implanted fiducial markers on these variations. Material/Methods: Ten esophageal cancer patients with at least two markers endoscopically implanted at the cranial and caudal tumor borders and visible on the planning computed tomography (pCT) were included in this study. Five dedicated gastrointestinal radiation oncologists independently delineated GTVs on the pCT without markers and with markers. The GTV was first delineated on pCTs where markers were digitally removed and next on the original pCT with markers. Both delineation series were executed twice to determine intra-observer variation. For both the inter- and intra-observer analyses, the generalized conformity index (CI_gen), and the standard deviation (SD) of the distances between delineated surfaces (i.e., overall, longitudinal, and radial SDs) were calculated. Linear mixed-effect models were used to compare the without and with markers series (α = 0.05). Results: Both the inter- and intra-observer CI_gen were significantly larger in the series with markers than in the series without markers (p < .001). For the series without markers vs. with markers, the inter-observer overall SD, longitudinal SD, and radial SD was 0.63 cm vs. 0.22 cm, 1.44 cm vs. 0.42 cm, and 0.26 cm vs. 0.18 cm, respectively (p < .05); moreover, the intra-observer overall SD, longitudinal SD, and radial SD was 0.45 cm vs. 0.26 cm, 1.10 cm vs. 0.41 cm, and 0.22 cm vs. 0.15 cm, respectively (p < .05). Conclusion: The presence of markers at the cranial and caudal tumor borders significantly reduced both inter- and intra-observer GTV delineation variation, especially in the longitudinal direction. Our results endorse the use of markers in GTV delineation for esophageal cancer patients.

Impact of hybrid FDG-PET/CT on gross tumor volume definition of cervical esophageal cancer: reducing interobserver variation

Intensity-modulated radiation therapy is being increasingly used to treat cervical esophageal cancer (CEC); however, delineating the gross tumor volume (GTV) accurately is essential for its successful treatment. The use of computed tomography (CT) images to determine the GTV produces a large degree of interobserver variation. In this study, we evaluated whether the use of [18F]-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET)/CT fused images reduced interobserver variation, compared with CT images alone, to determine the GTV in patients with CEC. FDG-PET/CT scans were obtained for 10 patients with CEC, imaged positioned on a flat tabletop with a pillow. Five radiation oncologists independently defined the GTV for the primary tumors using routine clinical data; they contoured the GTV based on CT images (GTVCT), followed by contouring based on FDG-PET/CT fused images (GTVPET/CT). To determine the geometric observer variation, we calculated the conformality index (CI) from the ratio of the intersection of the GTVs to their union. The interobserver CI was compared using Wilcoxon's signed rank test. The mean (±SD) interobserver CIs of GTVCT and GTVPET/CT were 0.39 ± 0.15 and 0.58 ± 0.10, respectively (P = 0.005). Our results suggested that FDG-PET/CT images reduced interobserver variation when determining the GTV in patients with CEC. FDG-PET/CT may increase the consistency of the radiographically determined GTV in patients with CEC.

Gross tumour delineation on computed tomography and positron emission tomography-computed tomography in oesophageal cancer: A nationwide study

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Interobserver variability in delineation of the oesophageal GTV can be considerable.

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Delineation variation is mainly located at the cranial and caudal border.

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PET significantly influences the delineated GTV in oesophageal cancer.

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The impact of PET to CT on observer variation of the GTV is limited.

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Accurate GTV delineation is essential for results of radiation boost-strategies.

Background and purpose

Accurate delineation of the primary tumour is vital to the success of radiotherapy and even more important for successful boost strategies, aiming for improved local control in oesophageal cancer patients. Therefore, the aim was to assess delineation variability of the gross tumour volume (GTV) between CT and combined PET-CT in oesophageal cancer patients in a multi-institutional study.

Materials and methods

Twenty observers from 14 institutes delineated the primary tumour of 6 cases on CT and PET-CT fusion. The delineated volumes, generalized conformity index (CIgen) and standard deviation (SD) in position of the most cranial/caudal slice over the observers were evaluated. For the central delineated region, perpendicular distance between median surface GTV and each individual GTV was evaluated as in-slice SD.

Results

After addition of PET, mean GTVs were significantly smaller in 3 cases and larger in 1 case. No difference in CIgen was observed (average 0.67 on CT, 0.69 on PET-CT). On CT cranial-caudal delineation variation ranged between 0.2 and 1.5 cm SD versus 0.2 and 1.3 cm SD on PET-CT. After addition of PET, the cranial and caudal variation was significantly reduced in 1 and 2 cases, respectively. The in-slice SD was on average 0.16 cm in both phases.

Conclusion

In some cases considerable GTV delineation variability was observed at the cranial-caudal border. PET significantly influenced the delineated volume in four out of six cases, however its impact on observer variation was limited.

Radiotherapy volume delineation using 18F-FDG-PET/CT modifies gross node volume in patients with oesophageal cancer

PURPOSE

Evidence supporting the use of 18F-FDG-PET/CT in the segmentation process of oesophageal cancer for radiotherapy planning is limited. Our aim was to compare the volumes and tumour lengths defined by fused PET/CT vs. CT simulation.

MATERIALS AND METHODS

Twenty-nine patients were analyzed. All patients underwent a single PET/CT simulation scan. Two separate GTVs were defined: one based on CT data alone and another based on fused PET/CT data. Volume sizes for both data sets were compared and the spatial overlap was assessed by the Dice similarity coefficient (DSC).

RESULTS

The gross tumour volume (GTVtumour) and maximum tumour diameter were greater by PET/CT, and length of primary tumour was greater by CT, but differences were not statistically significant. However, the gross node volume (GTVnode) was significantly greater by PET/CT. The DSC analysis showed excellent agreement for GTVtumour, 0.72, but was very low for GTVnode, 0.25.

CONCLUSIONS

Our study shows that the volume definition by PET/CT and CT data differs. CT simulation, without taking into account PET/CT information, might leave cancer-involved nodes out of the radiotherapy-delineated volumes.

Can CT scan protocols used for radiotherapy treatment planning be adjusted to optimize image quality and patient dose? A systematic review

This article reviews publications related to the use of CT scans for radiotherapy treatment planning, specifically the impact of scan protocol changes on CT number and treatment planning dosimetry and on CT image quality. A search on PubMed and EMBASE and a subsequent review of references yielded 53 relevant articles. CT scan parameters significantly affect image quality. Some will also affect Hounsfield unit (HU) values, though this is not comprehensively reported on. Changes in tube kilovoltage and, on some scanners, field of view and reconstruction algorithms have been found to produce notable HU changes. The degree of HU change which can be tolerated without changing planning dose by >1% depends on the body region and size, planning algorithms, treatment beam energy and type of plan. A change in soft-tissue HU value has a greater impact than changes in HU for bone and air. The use of anthropomorphic phantoms is recommended when assessing HU changes. There is limited published work on CT scan protocol optimization in radiotherapy. Publications suggest that HU tolerances of ±20 HU for soft tissue and of ±50 HU for the lung and bone would restrict dose changes in the treatment plan to <1%. Literature related to the use of CT images in radiotherapy planning has been reviewed to establish the acceptable level of HU change and the impact on image quality of scan protocol adjustment. Conclusions have been presented and further work identified.

Impact of Integrated PET/CT on Variability of Target Volume Delineation in Rectal Cancer

Several studies have demonstrated substantial variability among individual radiation oncologists in defining target volumes using computed tomography (CT). The objective of this study was to determine the impact of combined positron emission tomography and computed tomography (PET/CT) on inter-observer variability of target volume delineation in rectal cancer. We also compared the relative concordance of two PET imaging tracers, 18F-fluorodeoxyglucose (FDG) and 18F-fluorodeoxythymidine (FLT), against conventional computed tomography (CT). Six consecutive patients with locally advanced rectal cancer were enrolled onto an institutional protocol involving preoperative chemoradiotherapy and correlative studies including FDG- and FLT-PET scans acquired in the treatment position. Using these image data sets, four radiation oncologists independently delineated primary and nodal gross tumor volumes (GTVp and GTVn) for a hypothetical boost treatment. Contours were first defined based on CT alone with observers blinded to the PET images, then based on combined PET/CT. An inter-observer similarity index (SI), ranging from a value of 0 for complete disagreement to 1 for complete agreement of contoured voxels, was calculated for each set of volumes. For primary gross tumor volume (GTVp), the difference in estimated SI between CT and FDG was modest (CT SI = 0.77 vs. FDG SI = 0.81), but statistically significant (p = 0.013). The SI difference between CT and FLT for GTVp was also slight (FLT SI = 0.80) and marginally non-significant (p < 0.082). For nodal gross tumor volume, (GTVn), SI was significantly lower for CT based volumes with an estimated SI of 0.22 compared to an estimated SI of 0.70 for FDG-PET/CT (p < 0.0001) and an estimated SI of 0.70 for FLT-PET/CT (p < 0.0001). Boost target volumes in rectal cancer based on combined PET/CT results in lower inter-observer variability compared with CT alone, particularly for nodal disease. The use of FDG and FLT did not appear to be different from this perspective.

Uncertainties in target volume delineation in radiotherapy - are they relevant and what can we do about them?

Background

Modern radiotherapy techniques enable delivery of high doses to the target volume without escalating dose to organs at risk, offering the possibility of better local control while preserving good quality of life. Uncertainties in target volume delineation have been demonstrated for most tumour sites, and various studies indicate that inconsistencies in target volume delineation may be larger than errors in all other steps of the treatment planning and delivery process. The aim of this paper is to summarize the degree of delineation uncertainties for different tumour sites reported in the literature and review the effect of strategies to minimize them.

Conclusions

Our review confirmed that interobserver variability in target volume contouring represents the largest uncertainty in the process for most tumour sites, potentially resulting in a systematic error in dose delivery, which could influence local control in individual patients. For most tumour sites the optimal combination of imaging modalities for target delineation still needs to be determined. Strict use of delineation guidelines and protocols is advisable both in every day clinical practice and in clinical studies to diminish interobserver variability. Continuing medical education of radiation oncologists cannot be overemphasized, intensive formal training on interpretation of sectional imaging should be included in the program for radiation oncology residents.

Precise delineation of clinical target volume for crossing-segments thoracic esophageal squamous cell carcinoma based on the pattern of lymph node metastases

BACKGROUND

This work aims to investigate lymph node metastases (LNM) pattern of crossing-segments thoracic esophageal squamous cell carcinoma (ESCC) and its significance in clinical target volume (CTV) delineation.

METHODS

From January 2000 to December 2014, 3,587 patients with thoracic ESCC underwent surgery including esophagectomy and lymphadenectomy at Shandong Cancer Hospital and Institute. Information of tumor location based on preoperative endoscopic ultrasonography (EUS) and postoperative pathological results were retrospectively collected. The extent of the irradiation field was determined based on LNM pattern.

RESULTS

Among the patients reviewed, 1,501 (41.8%) were crossing-segments thoracic ESCC patients. The rate of LNM were 12.1%, 15.2%, 8.0%, 3.0%, and 7.1% in neck, upper mediastinum, middle mediastinum, lower mediastinum, and abdominal cavity for patients with upper-middle thoracic ESCC, 10.3%, 8.2%, 11.0%, 4.8%, 8.2% for middle-upper thoracic ESCC, 4.8%, 4.8%, 24.1%, 6.3%, 22.8% for middle-lower thoracic ESCC and 3.9%, 3.1%, 22.8%, 11.9%, 25.8% for lower-middle thoracic ESCC, respectively. The top three sites of LNM were 105 (12.1%), 108 (6.1%), 101 (6.1%) for upper-middle thoracic ESCC, 108 (8.2%), 105 (7.5%), 106 (6.8%) for middle-upper thoracic ESCC, 1 (18.8%), 108 (17.9%), 107 (9.6%) for middle-lower thoracic ESCC, 1 (21.3%), 108 (16.1%), 107 (10.1%) for lower-middle thoracic ESCC.

CONCLUSIONS

Crossing-segments thoracic ESCC was remarkably common among patients. When delineating their CTV, tumor location should be taken into consideration seriously. For upper-middle and middle-upper thoracic ESCC, abdominal cavity may be free from irradiation. For middle-lower and lower-middle thoracic ESCC, besides irradiation of relative mediastinal, irradiation of abdominal cavity can't be neglected.

Variations in CT determination of target volume with active breath co-ordinate in radiotherapy for post-operative gastric cancer

OBJECTIVE

To investigate interobserver and inter-CT variations in using the active breath co-ordinate technique in the determination of clinical tumour volume (CTV) and normal organs in post-operative gastric cancer radiotherapy.

METHODS

Ten gastric cancer patients were enrolled in our study, and four radiation oncologists independently determined the CTVs and organs at risk based on the CT simulation data. To determine interobserver and inter-CT variation, we evaluated the maximum dimensions, derived volume and distance between the centres of mass (CMs) of the CTVs. We assessed the reliability in CTV determination among the observers by conformity index (CI).

RESULTS

The average volumes ± standard deviation (cm(3)) of the CTV, liver, left kidney and right kidney were 674 ± 138 (range, 332-969), 1000 ± 138 (range, 714-1320), 149 ± 13 (range, 104-183) and 141 ± 21 (range, 110-186) cm(3), respectively. The average inter-CT distances between the CMs of the CTV, liver, left kidney and right kidney were 0.40, 0.56, 0.65 and 0.6 cm, respectively; the interobserver values were 0.98, 0.53, 0.16 and 0.15 cm, respectively.

CONCLUSIONS

In the volume size of CTV for post-operative gastric cancer, there were significant variations among multiple observers, whereas there was no variation between different CTs. The slices in which variations more likely occur were the slices of the lower verge of the hilum of the spleen and porta hepatis, then the paraoesophageal lymph nodes region and abdominal aorta, and the inferior vena cava, and the variation in the craniocaudal orientation from the interobserver was more predominant than that from inter-CT.

ADVANCES IN KNOWLEDGE

First, this is the first study to evaluate the interobserver and inter-CT variations in the determination of the CTV and normal organs in gastric cancer with the use of the active breath co-ordinate technique. Second, we analysed the region where variations most likely occur. Third, we investigated the influence of interobserver variation on the dose distribution.

Development of a software for quantitative evaluation radiotherapy target and organ-at-risk segmentation comparison

Modern radiotherapy requires accurate region of interest (ROI) inputs for plan optimization and delivery. Target delineation, however, remains operator-dependent and potentially serves as a major source of treatment delivery error. In order to optimize this critical, yet observer-driven process, a flexible web-based platform for individual and cooperative target delineation analysis and instruction was developed in order to meet the following unmet needs: (1) an open-source/open-access platform for automated/semiautomated quantitative interobserver and intraobserver ROI analysis and comparison, (2) a real-time interface for radiation oncology trainee online self-education in ROI definition, and (3) a source for pilot data to develop and validate quality metrics for institutional and cooperative group quality assurance efforts. The resultant software, Target Contour Testing/Instructional Computer Software (TaCTICS), developed using Ruby on Rails, has since been implemented and proven flexible, feasible, and useful in several distinct analytical and research applications.

Assessment of volume segmentation in radiotherapy of adolescents; a treatment planning study by the Swedish Workgroup for Paediatric Radiotherapy

BACKGROUND AND PURPOSE

The variability in target delineation for similar cases between centres treating paediatric and adolescent patients, and the apparent differences in interpretation of radiotherapy guidelines in the treatment protocols encouraged us to perform a dummy-run study as a part of our quality assurance work. The aim was to identify and quantify differences in the segmentation of target volumes and organs at risk (OARs) and to analyse the treatment plans and dose distributions.

MATERIALS AND METHODS

Four patient cases were selected: Wilm's tumour, Hodgkin's disease, rhabdomyosarcoma of the prostate and chordoma of the skull base. The five participating centres received the same patient-related material. They introduced the cases in their treatment planning system, delineated target volumes and OARs and created treatment plans. Dose-volume histograms were retrieved for relevant structures and volumes and dose metrics were derived and compared, e.g. target volumes and their concordance, dose homogeneity index (HI), treated and irradiated volumes, remaining volume at risk and relevant Vx and Dx values.

RESULTS

We found significant differences in target segmentation in the majority of the cases. The planning target volumes (PTVs) varied two- to four-fold and conformity indices were in the range of 0.3-0.6. This resulted in large variations in dose distributions to OARs as well as in treated and irradiated volumes even though the treatment plans showed good conformity to the PTVs. Potential reasons for the differences in target delineation were analysed.

CONCLUSION

Considerations of the growing child and difficulties in interpretation of the radiotherapy information in the treatment protocols were identified as reasons for the variation. As a result, clarified translated detailed radiotherapy guidelines for paediatric/adolescent patients have been recognised as a way to reduce this variation.

Does quality of radiation therapy predict outcomes of multicenter cooperative group trials? A literature review

Central review of radiation therapy (RT) delivery within multicenter clinical trials was initiated in the early 1970s in the United States. Early quality assurance publications often focused on metrics related to process, logistics, and timing. Our objective was to review the available evidence supporting correlation of RT quality with clinical outcomes within cooperative group trials. A MEDLINE search was performed to identify multicenter studies that described central subjective assessment of RT protocol compliance (quality). Data abstracted included method of central review, definition of deviations, and clinical outcomes. Seventeen multicenter studies (1980-2012) were identified, plus one Patterns of Care Study. Disease sites were hematologic, head and neck, lung, breast, and pancreas. Between 0 and 97% of treatment plans received an overall grade of acceptable. In 7 trials, failure rates were significantly higher after inadequate versus adequate RT. Five of 9 and 2 of 5 trials reported significantly worse overall and progression-free survival after poor-quality RT, respectively. One reported a significant correlation, and 2 reported nonsignificant trends toward increased toxicity with noncompliant RT. Although more data are required, protocol-compliant RT may decrease failure rates and increase overall survival and likely contributes to the ability of collected data to answer the central trial question.

The value of endoscopic ultrasonography in defining longitudinal gross target volumes for esophageal squamous carcinoma

BACKGROUND AND PURPOSE

To investigate the differences between endoscopic ultrasonography (EUS)-based longitudinal gross target volumes (GTV) (GTV(EUS)) and computed tomography (CT)-based longitudinal GTV (GTV(CT)) in diagnosing esophageal squamous carcinoma.

METHODS

Thirty-six patients underwent EUS to define the superior and inferior extents of the tumor by using hemoclips. CT-planning scan was performed with the patient in the supine position during the treatment. GTV(CT) and GTV(EUS) were contoured respectively. The respective lengths (L(CT) and L(EUS)) and spatial locations of longitudinal GTV(CT) and longitudinal GTV(EUS) were compared.

RESULTS

The mean LCT was 7.8 ± 3.2 cm and the mean L(EUS) was 7.4 ± 2.7 cm. No statistical difference was found between L(CT) and L(EUS) (P > 0.05) with a correlation coefficient of 0.61 (P<0.05). The mean conformal index was 0.79 ± 0.18 with spatial variations found in 71% (24/34) of the patients.

CONCLUSIONS

EUS can provide additional information to CT in defining longitudinal GTV in thoracic esophageal squamous cell carcinoma, especially superficial and submucosal carcinomas, which may contribute to the development of better individual treatment regimens.

Automated Delineation of Lung Tumors from CT Images Using a Single Click Ensemble Segmentation Approach

A single click ensemble segmentation (SCES) approach based on an existing "Click&Grow" algorithm is presented. The SCES approach requires only one operator selected seed point as compared with multiple operator inputs, which are typically needed. This facilitates processing large numbers of cases. Evaluation on a set of 129 CT lung tumor images using a similarity index (SI) was done. The average SI is above 93% using 20 different start seeds, showing stability. The average SI for 2 different readers was 79.53%. We then compared the SCES algorithm with the two readers, the level set algorithm and the skeleton graph cut algorithm obtaining an average SI of 78.29%, 77.72%, 63.77% and 63.76% respectively. We can conclude that the newly developed automatic lung lesion segmentation algorithm is stable, accurate and automated.

Radiomics: the process and the challenges

"Radiomics" refers to the extraction and analysis of large amounts of advanced quantitative imaging features with high throughput from medical images obtained with computed tomography, positron emission tomography or magnetic resonance imaging. Importantly, these data are designed to be extracted from standard-of-care images, leading to a very large potential subject pool. Radiomics data are in a mineable form that can be used to build descriptive and predictive models relating image features to phenotypes or gene-protein signatures. The core hypothesis of radiomics is that these models, which can include biological or medical data, can provide valuable diagnostic, prognostic or predictive information. The radiomics enterprise can be divided into distinct processes, each with its own challenges that need to be overcome: (a) image acquisition and reconstruction, (b) image segmentation and rendering, (c) feature extraction and feature qualification and (d) databases and data sharing for eventual (e) ad hoc informatics analyses. Each of these individual processes poses unique challenges. For example, optimum protocols for image acquisition and reconstruction have to be identified and harmonized. Also, segmentations have to be robust and involve minimal operator input. Features have to be generated that robustly reflect the complexity of the individual volumes, but cannot be overly complex or redundant. Furthermore, informatics databases that allow incorporation of image features and image annotations, along with medical and genetic data, have to be generated. Finally, the statistical approaches to analyze these data have to be optimized, as radiomics is not a mature field of study. Each of these processes will be discussed in turn, as well as some of their unique challenges and proposed approaches to solve them. The focus of this article will be on images of non-small-cell lung cancer.

Interobserver variation in parotid gland delineation: a study of its impact on intensity-modulated radiotherapy solutions with a systematic review of the literature

OBJECTIVES

This study evaluates the interobserver variation in parotid gland delineation and its impact on intensity-modulated radiotherapy (IMRT) solutions.

METHODS

The CT volumetric data sets of 10 patients with oropharyngeal squamous cell carcinoma who had been treated with parotid-sparing IMRT were used. Four radiation oncologists and three radiologists delineated the parotid gland that had been spared using IMRT. The dose-volume histogram (DVH) for each study contour was calculated using the IMRT plan actually delivered for that patient. This was compared with the original DVH obtained when the plan was used clinically.

RESULTS

70 study contours were analysed. The mean parotid dose achieved during the actual treatment was within 10% of 24 Gy for all cases. Using the study contours, the mean parotid dose obtained was within 10% of 24 Gy for only 53% of volumes by radiation oncologists and 55% of volumes by radiologists. The parotid DVHs of 46% of the study contours were sufficiently different from those used clinically, such that a different IMRT plan would have been produced.

CONCLUSION

Interobserver variation in parotid gland delineation is significant. Further studies are required to determine ways of improving the interobserver consistency in parotid gland definition.

Interobserver variation in clinical target volume and organs at risk segmentation in post-parotidectomy radiotherapy: can segmentation protocols help?

OBJECTIVE

A study of interobserver variation in the segmentation of the post-operative clinical target volume (CTV) and organs at risk (OARs) for parotid tumours was undertaken. The segmentation exercise was performed as a baseline, and repeated after 3 months using a segmentation protocol to assess whether CTV conformity improved.

METHODS

Four head and neck oncologists independently segmented CTVs and OARs (contralateral parotid, spinal cord and brain stem) on CT data sets of five patients post parotidectomy. For each CTV or OAR delineation, total volume was calculated. The conformity level (CL) between different clinicians' outlines was measured using a validated outline analysis tool. The data for CTVs were re-analysed after using the cochlear sparing therapy and conventional radiation segmentation protocol.

RESULTS

Significant differences in CTV morphology were observed at baseline, yielding a mean CL of 30% (range 25-39%). The CL improved after using the segmentation protocol with a mean CL of 54% (range 50-65%). For OARs, the mean CL was 60% (range 53-68%) for the contralateral parotid gland, 23% (range 13-27%) for the brain stem and 25% (range 22-31%) for the spinal cord.

CONCLUSIONS

There was low conformity for CTVs and OARs between different clinicians. The CL for CTVs improved with use of a segmentation protocol, but the CLs remained lower than expected. This study supports the need for clear guidelines for segmentation of target and OARs to compare and interpret the results of head and neck cancer radiation studies.

Toward semi-automated assessment of target volume delineation in radiotherapy trials: the SCOPE 1 pretrial test case

PURPOSE

To evaluate different conformity indices (CIs) for use in the analysis of outlining consistency within the pretrial quality assurance (Radiotherapy Trials Quality Assurance [RTTQA]) program of a multicenter chemoradiation trial of esophageal cancer and to make recommendations for their use in future trials.

METHODS AND MATERIALS

The National Cancer Research Institute SCOPE 1 trial is an ongoing Cancer Research UK-funded phase II/III randomized controlled trial of chemoradiation with capecitabine and cisplatin with or without cetuximab for esophageal cancer. The pretrial RTTQA program included a detailed radiotherapy protocol, an educational package, and a single mid-esophageal tumor test case that were sent to each investigator to outline. Investigator gross tumor volumes (GTVs) were received from 50 investigators in 34 UK centers, and CERR (Computational Environment for Radiotherapy Research) was used to perform an assessment of each investigator GTV against a predefined gold-standard GTV using different CIs. A new metric, the local conformity index (l-CI), that can localize areas of maximal discordance was developed.

RESULTS

The median Jaccard conformity index (JCI) was 0.69 (interquartile range, 0.62-0.70), with 14 of 50 investigators (28%) achieving a JCI of 0.7 or greater. The median geographical miss index was 0.09 (interquartile range, 0.06-0.16), and the mean discordance index was 0.27 (95% confidence interval, 0.25-0.30). The l-CI was highest in the middle section of the volume, where the tumor was bulky and more easily definable, and identified 4 slices where fewer than 20% of investigators achieved an l-CI of 0.7 or greater.

CONCLUSIONS

The available CIs analyze different aspects of a gold standard-observer variation, with JCI being the most useful as a single metric. Additional information is provided by the l-CI and can focus the efforts of the RTTQA team in these areas, possibly leading to semi-automated outlining assessment.

Interobserver variability in target volume delineation in postoperative radiochemotherapy for gastric cancer. A pilot prospective study

INTRODUCTION

The aim of this study is to determine the interobserver variability (IV) between radiation oncologists (RO) in target volume delineation for postoperative gastric cancer (GC) radiotherapy planning.

MATERIALS AND METHODS

Four physicians were asked to delimitate clinical target volume (CTV) on the same 3D CT images in 9 postoperative radiochemotherapy GC patients. Instructions were given to include tumour bed, remaining stomach, anastomosis, duodenal loop and local lymph nodes. The principal variable was spatial volume discrepancy between the main observer (called "A") and other observers (all called "B"), which were compared using the mathematical formula A⌣B/A⌢B, applied to the 3D CT images using Boolean operators. Analysis of variance with two random effects (observers and patients) was performed.

RESULTS

Mean volumes were 1410 cm(3) for OBA, 1231 cm(3) for OB2, 734.6 cm(3) for OB3 and 1350 cm(3) for OB4. Discrepancies were 519.9±431.6 cm(3) for OB2, 652.1±294.36 cm(3) for OB3 and 225.90±237.07 cm(3) for OB4. Standard deviation ascribed to patients as random effect was 898.6 cm(3) and that ascribed to observers was 198.10 cm(3), considered as a statistically significant difference.

CONCLUSIONS

A significant IV in target delineation that can be attributed to many factors depends more on patients' characteristics than RO delineating decisions.

Human-computer interaction in radiotherapy target volume delineation: a prospective, multi-institutional comparison of user input devices

The purpose of this study was the prospective comparison of objective and subjective effects of target volume region of interest (ROI) delineation using mouse-keyboard and pen-tablet user input devices (UIDs). The study was designed as a prospective test/retest sequence, with Wilcoxon signed rank test for matched-pair comparison. Twenty-one physician-observers contoured target volume ROIs on four standardized cases (representative of brain, prostate, lung, and head and neck malignancies) twice: once using QWERTY keyboard/scroll-wheel mouse UID and once with pen-tablet UID (DTX2100, Wacom Technology Corporation, Vancouver, WA, USA). Active task time, ROI manipulation task data, and subjective survey data were collected. One hundred twenty-nine target volume ROI sets were collected, with 62 paired pen-tablet/mouse-keyboard sessions. Active contouring time was reduced using the pen-tablet UID, with mean ± SD active contouring time of 26 ± 23 min, compared with 32 ± 25 with the mouse (p ≤ 0.01). Subjective estimation of time spent was also reduced from 31 ± 26 with mouse to 27 ± 22 min with the pen (p = 0.02). Task analysis showed ROI correction task reduction (p = 0.045) and decreased panning and scrolling tasks (p < 0.01) with the pen-tablet; drawing, window/level changes, and zoom commands were unchanged (p = n.s.) Volumetric analysis demonstrated no detectable differences in ROI volume nor intra- or inter-observer volumetric coverage. Fifty-two of 62 (84%) users preferred the tablet for each contouring task; 5 of 62 (8%) denoted no preference, and 5 of 62 (8%) chose the mouse interface. The pen-tablet UID reduced active contouring time and reduced correction of ROIs, without substantially altering ROI volume/coverage.

Multidisciplinary collaborative gross tumour volume definition for lung cancer radiotherapy: a prospective study

Variability in gross tumour volume (GTV) definition is a major source of systematic error in conformal radiotherapy. This prospective study assesses the role of multidisciplinary collaboration between oncologists and radiologists in defining lung cancer volumes. Twenty patients with non-small cell lung cancer due to receive three-dimensional conformal radiotherapy formed the study population. GTVs were defined by a radiologist (GTVrad) and an oncologist (GTVonc) using available clinical information and imaging. A collaborative meeting was then held to agree on a final, common GTV (GTVfin) to be used for treatment planning, and differences analysed. The collaboration changed the GTV in 19/20 patients with a total of 50 regions being edited. Changes made were categorized as (a) differentiation of tumour from atelectasis or ground glass shadowing, (b) separation of tumour from vasculature, and (c) defining mediastinal extent of tumour. Oncologists were more confident in the GTVfin than the GTVonc. The radiologist took longer to define the GTV than the oncologist. Real-time collaborative GTV definition by a radiologist and oncologist is practical and feasible. This approach allows specific areas of uncertainty to be categorized and focussed on, reducing systematic error in GTV definition. The physician's approach to risk and decision making for each patient may also play a role.

Postoperative extended-volume external-beam radiation therapy in high-risk esophageal cancer patients: a prospective experience

Background and Purpose

Extended-volume external-beam radiation therapy (rt) following esophagectomy is controversial. The present prospective study evaluates the feasibility of extended-volume rt treatment in high-risk esophagectomy patients with a cervical anastomosis receiving postoperative combined chemoradiation therapy.

Patients and Methods

From 2001 to 2006, 15 patients with resected esophageal cancer were prospectively accrued to this pilot study to evaluate the adverse effects of extended-volume rt. Postoperative management was carried out at London Regional Cancer Program. Eligibility criteria were pathology-proven esophageal malignancy (T3–4, N0–1), disease amenable to surgical resection, and esophagectomy with or without resection margin involvement. Patients with distant metastases (M1) and patients treated with previous rt were excluded. All 15 study patients received 4 cycles of 5-fluorouracil–based chemotherapy. External-beam rt was conducted using conformal computed tomography planning, with multi-field arrangement tailored to the pathology findings, with coverage of a clinical target volume encompassing the primary tumour bed and the anastomotic site in the neck. The radiation therapy dose was 50.40 Gy at 1.8 Gy per fraction. The rt was delivered concurrently with the third cycle of chemotherapy. The study outcomes—disease-free survival (dfs) and overall survival (os)—were calculated by the Kaplan–Meier method. Treatment-related toxicities were assessed using the U.S. National Cancer Institute’s Common Toxicity Criteria.

Results

The study accrued 10 men and 5 women of median age 64 years (range: 48–80 years) and TNM stages T3N0 (n = 1), T2N1 (n = 2), T3N1 (n = 11), and T4N1 (n = 1). Histopathology included 5 adenocarcinomas and 10 squamous-cell carcinomas. Resection margins were clear in 10 patients. The median follow-up time was 19 months (range: 3.5–53.4 months). Before radiation therapy commenced, delay in chemotherapy occurred in 20% of patients, and dose reduction was required in 13.3%. During the concurrent chemoradiation therapy phase, 20% of the patients experienced chemotherapy delay, and 6.6% experienced dose reduction. No patient experienced treatment-related acute and chronic esophagitis above grade 2. Disease recurred in 40% of the patients (6/15), and median time to relapse was 24 months. No tumour recurred at the anastomotic site. The median dfs was 23 months, and the median os was 21 months.

Conclusions

Extended-volume external-beam rt encompassing the tumour bed and the anastomotic site is feasible and safe for high-risk T3–4, N0–1 esophageal cancer patients after esophagectomy.

Interobserver variability of clinical target volume delineation in supra-diaphragmatic Hodgkin's disease: a multi-institutional experience

BACKGROUND

To determine interobserver variability in clinical target volume (CTV) of supra-diaphragmatic Hodgkin's lymphoma.

MATERIALS AND METHODS

At the 2008 AIRO (Italian Society of Radiation Oncology) Meeting, the Radiation Oncology Department of Chieti proposed a multi-institutional contouring dummy-run of two cases of early stage supra-diaphragmatic Hodgkin's lymphoma after chemotherapy. Clinical history, diagnostics, and planning CT imaging were available on Chieti's radiotherapy website (www.radioterapia.unich.it). Participating centers were requested to delineate the CTV and submit it to the coordinating center. To quantify interobserver variability of CTV delineations, the total volume, craniocaudal, laterolateral, and anteroposterior diameters were calculated.

RESULTS

A total of 18 institutions for case A and 15 institutions for case B submitted the targets. Case A presented significant variability in total volume (range: 74.1-1,157.1 cc), craniocaudal (range: 6.5-22.5 cm; median: 16.25 cm), anteroposterior (range: 5.04-14.82 cm; median: 10.28 cm), and laterolateral diameters (range: 8.23-22.88 cm; median: 15.5 cm). Mean CTV was 464.8 cc (standard deviation: 280.5 cc). Case B presented significant variability in total volume (range: 341.8-1,662 cc), cranio-caudal (range: 8.0-28.5 cm; median: 23 cm), anteroposterior (range: 7.9-1.8 cm; median: 11.1 cm), and laterolateral diameters (range: 12.9-24.0 cm; median: 18.8 cm). Mean CTV was 926.0 cc (standard deviation: 445.7 cc).

CONCLUSION

This significant variability confirms the need to apply specific guidelines to improve contouring uniformity in Hodgkin's lymphoma.

A review of methods of analysis in contouring studies for radiation oncology

Inter-observer variability in anatomical contouring is the biggest contributor to uncertainty in radiation treatment planning. Contouring studies are frequently performed to investigate the differences between multiple contours on common datasets. There is, however, no widely accepted method for contour comparisons. The purpose of this study is to review the literature on contouring studies in the context of radiation oncology, with particular consideration of the contouring comparison methods they employ. A literature search, not limited by date, was conducted using Medline and Google Scholar with key words: contour, variation, delineation, inter/intra observer, uncertainty and trial dummy-run. This review includes a description of the contouring processes and contour comparison metrics used. The use of different processes and metrics according to tumour site and other factors were also investigated with limitations described. A total of 69 relevant studies were identified. The most common tumour sites were prostate (26), lung (10), head and neck cancers (8) and breast (7).The most common metric of comparison was volume used 59 times, followed by dimension and shape used 36 times, and centre of volume used 19 times. Of all 69 publications, 67 used a combination of metrics and two used only one metric for comparison. No clear relationships between tumour site or any other factors that may influence the contouring process and the metrics used to compare contours were observed from the literature. Further studies are needed to assess the advantages and disadvantages of each metric in various situations.

Quantifying interobserver variation in target definition in palliative radiotherapy

PURPOSE

To describe the degree of interobserver and intraobserver variability in target and field definition when using three-dimensional (3D) volume- vs. two-dimensional (2D) field-based planning.

METHODS AND MATERIALS

Standardized case scenario and diagnostic imaging for 9 palliative cases (3 bone metastases, 3 palliative lung cancer, and 3 abdominal pelvis soft-tissue disease) were presented to 5 study radiation oncologists. After a decision on what the intended anatomic target should be, observers created two sets of treatment fields, first using a 2D field-based and then a 3D volume-based planning approach. Percent overlap, under-coverage, and over-coverage were used to describe interobserver and intraobserver variations in target definition.

RESULTS

The degree of interobserver variation for 2D and 3D planning was similar with a degree of overlap of 76% (range, 56%-85%) and 74% (range, 55%-88%), respectively. When comparing the treatment fields defined by the same observer using the two different planning methods, the mean degree of overlap was 78%; over-coverage, 22%; and under-coverage, 41%. There was statistically significantly more under-coverage when field-based planning was used for bone metastases (33%) vs. other anatomic sites (16%) (p = 0.02). In other words, 2D planning is more likely to result in geographic misses in bone metastases compared with other areas.

CONCLUSIONS

In palliative radiotherapy clinically significant interobserver and intraobserver variation existed when using both field- and volume-based planning approaches. Strategies that would reduce this variability deserve further investigation.

Computed tomography overestimation of esophageal tumor length: Implications for radiotherapy planning

AIM: To assess the relationship between preoperative computed tomography (CT) and postoperative pathological measurements of esophageal tumor length and the prognostic significance of CT tumor length data.

METHODS: A retrospective study was carried out in 56 patients who underwent curative esophagogastrectomy. Tumor lengths were measured on the immediate preoperative CT and on the post-operative resection specimens. Inter- and intra-observer variations in CT measurements were assessed. Survival data were collected.

RESULTS: There was a weak correlation between CT and pathological tumor length (r = 0.30, P = 0.025). CT lengths were longer than pathological lengths in 68% (38/56) of patients with a mean difference of 1.67 cm (95% CI: 1.18-2.97). The mean difference in measurements by two radiologists was 0.39 cm (95% CI: -0.59-1.44). The mean difference between repeat CT measured tumor length (intra-observer variation) were 0.04 cm (95% CI: -0.59-0.66) and 0.47 cm (95% CI: -0.53-1.47). When stratified, patients not receiving neoadjuvant chemotherapy showed a strong correlation between CT and pathological tumor length (r = 0.69, P = 0.0014, n = 37) than patients that did (r = 0.13, P = 0.43, n = 19). Median survival with CT tumor length > 5.6 cm was poorer than with smaller tumors, but the difference was not statistically significant.

CONCLUSION: Esophageal tumor length assessed using CT does not reflect pathological tumor extent and should not be the only modality used for management decisions, particularly for planning radiotherapy.

Three-dimensional conformal radiation therapy for esophageal squamous cell carcinoma: is elective nodal irradiation necessary?

PURPOSE

To evaluate the local control, survival, and toxicity associated with three-dimensional conformal radiotherapy (3D-CRT) for squamous cell carcinoma (SCC) of the esophagus, to determine the appropriate target volumes, and to determine whether elective nodal irradiation is necessary in these patients.

METHODS AND MATERIALS

A prospective study of 3D-CRT was undertaken in patients with esophageal SCC without distant metastases. Patients received 68.4 Gy in 41 fractions over 44 days using late-course accelerated hyperfractionated 3D-CRT. Only the primary tumor and positive lymph nodes were irradiated. Isolated out-of-field regional nodal recurrence was defined as a recurrence in an initially uninvolved regional lymph node.

RESULTS

All 53 patients who made up the study population tolerated the irradiation well. No acute or late Grade 4 or 5 toxicity was observed. The median survival time was 30 months (95% confidence interval, 17.7-41.8). The overall survival rate at 1, 2, and 3 years was 77%, 56%, and 41%, respectively. The local control rate at 1, 2, and 3 years was 83%, 74%, and 62%, respectively. Thirty-nine of the 53 patients (74%) showed treatment failure. Seventeen of the 39 (44%) developed an in-field recurrence, 18 (46%) distant metastasis with or without regional failure, and 3 (8%) an isolated out-of-field nodal recurrence only. One patient died of disease in an unknown location.

CONCLUSIONS

In patients treated with 3D-CRT for esophageal SCC, the omission of elective nodal irradiation was not associated with a significant amount of failure in lymph node regions not included in the planning target volume. Local failure and distant metastases remained the predominant problems.

Conformal radiotherapy for lung cancer: interobservers' variability in the definition of gross tumor volume between radiologists and radiotherapists

Background

Conformal external radiotherapy aims to improve tumor control by boosting tumor dose, reducing morbidity and sparing healthy tissues. To meet this objective careful visualization of the tumor and adjacent areas is required. However, one of the major issues to be solved in this context is the volumetric definition of the targets. This study proposes to compare the gross volume of lung tumors as delineated by specialized radiologists and radiotherapists of a cancer center.

Methods

Chest CT scans of a total of 23 patients all with non-small cell lung cancer, not submitted to surgery, eligible and referred to conformal radiotherapy on the Hospital A. C. Camargo (São Paulo, Brazil), during the year 2004 were analyzed. All cases were delineated by 2 radiologists and 2 radiotherapists. Only the gross tumor volume and the enlarged lymph nodes were delineated. As such, four gross tumor volumes were achieved for each one of the 23 patients.

Results

There was a significant positive correlation between the 2 measurements (among the radiotherapists, radiologists and intra-class) and there was randomness in the distribution of data within the constructed confidence interval.

Conclusion

There were no significant differences in the definition of gross tumor volume between radiologists and radiotherapists.

The potential of proton beam radiation therapy in gastrointestinal cancer

A group of Swedish oncologists and hospital physicists have estimated the number of patients in Sweden suitable for proton beam therapy. The estimations have been based on current statistics of tumour incidence, number of patients potentially eligible for radiation treatment, scientific support from clinical trials and model dose planning studies and knowledge of the dose-response relations of different tumours and normal tissues. In gastrointestinal cancers, it is assessed that at least 345 patients, mainly non-resectable rectal cancers, oesophageal and liver cancers, are eligible. Great uncertainties do however exist both in the number of patients with gastrointestinal cancers suitable for radiation therapy, and in the proportion of those where proton beams may give sufficiently better results.

Physical considerations on discrepancies in target volume delineation

BACKGROUND AND PURPOSE

To compare the delineations and interpretations of target volumes by physicians in different radio-oncology centers.

MATERIALS AND METHODS

Eleven Swiss radio-oncology centers delineated volumes according to ICRU 50 recommendations for one prostate and one head and neck case. In order to evaluate the consistency of the volume delineations, the following parameters were determined: 1) the target volumes (GTV, CTV and manually expanded PTV) and their extensions in the three main axes and 2) the correlation of the volume delineated by each pair of centers using the ratio of the intersection to the union (called proximity index).

RESULTS

The delineated prostate volume was 105+/-55 cm(3) for the CTV and 218+/-44 cm(3) for the PTV. The delineated head and neck volume was 46+/-15 cm(3) for the GTV, 327+/-154 cm(3) for the CTV and 528+/-106 cm(3) for the PTV. The mean proximity index for the prostate case was 0.50+/-0.13 for the CTV and 0.57+/-0.11 for the PTV. The proximity index for the head and neck case was 0.45+/-0.09 for the GTV, 0.42+/-0.13 for the CTV and 0.59+/-0.06 for the PTV.

CONCLUSIONS

Large discrepancies between all the delineated target volumes were observed. There was an inverse relationship between the CTV volume and the margin between CTV and PTV, leading to less discrepancies in the PTV than is the CTV delineations. There was more spread in the sagittal and frontal planes due to CT pixel anisotropy, which suggests that radiation oncologists should delineate the target volumes not only in the transverse plane, but also in the sagittal and frontal planes to improve the delineation by allowing a consistency check.

Variability of target and normal structure delineation for breast cancer radiotherapy: an RTOG Multi-Institutional and Multiobserver Study

PURPOSE

To quantify the multi-institutional and multiobserver variability of target and organ-at-risk (OAR) delineation for breast-cancer radiotherapy (RT) and its dosimetric impact as the first step of a Radiation Therapy Oncology Group effort to establish a breast cancer atlas.

METHODS AND MATERIALS

Nine radiation oncologists specializing in breast RT from eight institutions independently delineated targets (e.g., lumpectomy cavity, boost planning target volume, breast, supraclavicular, axillary and internal mammary nodes, chest wall) and OARs (e.g., heart, lung) on the same CT images of three representative breast cancer patients. Interobserver differences in structure delineation were quantified regarding volume, distance between centers of mass, percent overlap, and average surface distance. Mean, median, and standard deviation for these quantities were calculated for all possible combinations. To assess the impact of these variations on treatment planning, representative dosimetric plans based on observer-specific contours were generated.

RESULTS

Variability in contouring the targets and OARs between the institutions and observers was substantial. Structure overlaps were as low as 10%, and volume variations had standard deviations up to 60%. The large variability was related both to differences in opinion regarding target and OAR boundaries and approach to incorporation of setup uncertainty and dosimetric limitations in target delineation. These interobserver differences result in substantial variations in dosimetric planning for breast RT.

CONCLUSIONS

Differences in target and OAR delineation for breast irradiation between institutions/observers appear to be clinically and dosimetrically significant. A systematic consensus is highly desirable, particularly in the era of intensity-modulated and image-guided RT.

Coregistered FDG PET/CT-based textural characterization of head and neck cancer for radiation treatment planning

Coregistered fluoro-deoxy-glucose (FDG) positron emission tomography/computed tomography (PET/CT) has shown potential to improve the accuracy of radiation targeting of head and neck cancer (HNC) when compared to the use of CT simulation alone. The objective of this study was to identify textural features useful in distinguishing tumor from normal tissue in head and neck via quantitative texture analysis of coregistered 18F-FDG PET and CT images. Abnormal and typical normal tissues were manually segmented from PET/CT images of 20 patients with HNC and 20 patients with lung cancer. Texture features including some derived from spatial grey-level dependence matrices (SGLDM) and neighborhood gray-tone-difference matrices (NGTDM) were selected for characterization of these segmented regions of interest (ROIs). Both K nearest neighbors (KNNs) and decision tree (DT)-based KNN classifiers were employed to discriminate images of abnormal and normal tissues. The area under the curve (AZ) of receiver operating characteristics (ROC) was used to evaluate the discrimination performance of features in comparison to an expert observer. The leave-one-out and bootstrap techniques were used to validate the results. The AZ of DT-based KNN classifier was 0.95. Sensitivity and specificity for normal and abnormal tissue classification were 89% and 99%, respectively. In summary, NGTDM features such as PET Coarseness, PET Contrast, and CT Coarseness extracted from FDG PET/CT images provided good discrimination performance. The clinical use of such features may lead to improvement in the accuracy of radiation targeting of HNC.

Dosimetric comparison of IMRT vs. 3D conformal radiotherapy in the treatment of cancer of the cervical esophagus

BACKGROUND AND PURPOSE

Radiotherapy planning for cervical esophageal cancer is challenging. We compared IMRT and 3D conformal radiotherapy (CRT) with respect to conformality of target coverage and normal tissue sparing.

MATERIALS AND METHODS

We selected five patients with cervical esophagus cancer, who represented the heterogeneity of clinical cases, treated to radical dose and planned with Pinnacle v6.2. Target doses for CRT plans were 50, 60, and 70Gy (single-phase IMRT 56, 63, and 70). We compared PTV coverage by the 95% isodose (PTV(95)), conformality ratio (CR), conformation number (CN), and maximum or mean doses (D(max), D(mean)) to normal structures.

RESULTS

Median PTV(95) for IMRT plans for PTV70, PTV63, and PTV56 were 97%, 99%, and 98% (CRT 91%, 98%, and 85%). IMRT plans demonstrated lower D(max) to the spinal cord and brainstem (42 and 36Gy) compared to CRT (46 and 39Gy). Median left parotid D(mean) was 35Gy (IMRT) vs. 53Gy (CRT). Median right parotid D(mean) was 35Gy (IMRT) vs. 36Gy (CRT). The median CR50/56Gy was 1.4 (CRT) vs. 1.2 (IMRT), CR70Gy 1.7 (CRT) vs. 1.1 (IMRT). CN50/56 and CN70 values were 0.80 and 0.85 (IMRT) vs. 0.56 and 0.5 (CRT).

CONCLUSIONS

IMRT provides superior target volume coverage and conformality, with decreased dose to normal structures.