Four-dimensional measurement of the displacement of internal fiducial markers during 320-multislice computed tomography scanning of thoracic esophageal cancer

van Lier A, Mook S, Meijer GJ. Intrafraction motion analysis in online adaptive radiotherapy for esophageal cancer

Intrafraction motion during magnetic resonance (MR)-guided dose delivery of esophageal cancer tumors was retrospectively analyzed. Deformable image registration of cine-MR series resulted in gross tumor volume motion profiles in all directions, which were subsequently filtered to isolate respiratory and drift motion. A large variability in intrafraction motion patterns was observed between patients. Median 95% peak-to-peak motion was 7.7 (3.7 - 18.3) mm, 2.1 (0.7 - 5.7) mm and 2.4 (0.5 - 5.6) mm in cranio-caudal, left-right and anterior-posterior directions, relatively. Furthermore, intrafraction drift was generally modest (<5mm). A patient specific approach could lead to very small margins (<3mm) for most patients.

A comprehensive motion analysis - consequences for high precision image-guided radiotherapy of esophageal cancer patients

BACKGROUND AND PURPOSE

When treating patients for esophageal cancer (EC) with photon or proton radiotherapy (RT), breathing motion of the target and neighboring organs may result in deviations from the planned dose distribution. The aim of this study was to evaluate the magnitude and dosimetric impact of breathing motion. Results were based on comparing weekly 4D computed tomography (4D CT) scans with the planning CT, using the diaphragm as an anatomical landmark for EC.

MATERIAL AND METHODS

A total of 20 EC patients were included in this study. Diaphragm breathing amplitudes and off-sets (changes in position with respect to the planning CT) were determined from delineated left diaphragm structures in weekly 4D CT-scans. The potential dosimetric impact of respiratory motion was shown in several example patients for photon and proton radiotherapy.

RESULTS

Variation in diaphragm amplitudes were relatively small and ranged from 0 to 0.8 cm. However, the measured off-sets were larger, ranging from -2.1 to 1.9 cm. Of the 70 repeat CT-scans, the off-set exceeded the ITV-PTV margin of 0.8 cm during expiration in 4 CT-scans (5.7%) and during inspiration in 13 CT-scans (18.6%). The dosimetric validation revealed under- and overdosages in the VMAT and IMPT plans.

CONCLUSIONS

Despite relatively constant breathing amplitudes, the variation in the diaphragm position (off-set), and consequently tumor position, was clinically relevant. These motion effects may result in either treatments that miss the target volume, or dose deviations in the form of highly localized over- or underdosed regions.

The use of tumour markers in oesophageal cancer to quantify setup errors and baseline shifts during treatment

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Implantation of solid gold markers safe.

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Inter-fractional motion for markers in distal oesophagus largest cranio-caudally.

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Reduced radiotherapy treatment margins with soft-tissue vs. bony-anatomy matching.

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Impact of intra-fractional baseline shifts on margin calculation rather small.

Purpose

To prospectively evaluate the feasibility of solid gold marker placement in oesophageal cancer patients and to quantify inter-fractional and intra-fractional (baseline shift) marker motion during radiation treatment. Radiotherapy target margins and matching strategies were investigated.

Materials/methods

Thirty-four markers were implanted by echo-endoscopy in 10 patients. Patients received a planning 4D CT, daily pre-treatment cone-beam CT (CBCT) and a post-treatment CBCT for at least five fractions. For fractions with both pre- and post-treatment CBCT, marker displacement between planning CT and pre-treatment CBCT (inter-fractional) and between pre-treatment and post-treatment CBCT (intra-fractional; only for fractions without rotational treatment couch correction) were calculated in left–right (LR), cranio-caudal (CC) and anterior-posterior (AP) direction after bony-anatomy and soft-tissue matching. Systematic/random setup errors were estimated; treatment margins were calculated.

Results

No serious adverse events occurred. Twenty-three (67.6%) markers were visible during radiotherapy (n = 3 middle oesophagus, n = 16 distal oesophagus, n = 4 proximal stomach). Margins for inter-fractional displacement after bony-anatomy match depended on the localisation of the primary tumour and were 11.2 mm (LR), 16.4 mm (CC) and 8.2 mm (AP) for distal markers. Soft-tissue matching reduced the CC margin for these markers (16.4 mm to 10.5 mm). The mean intra-fractional shift of 12 distal markers was 0.4 mm (LR), 2.3 mm (CC) and 0.7 mm (AP). Inclusion of this shift resulted in treatment margins for distal markers of 12.8 mm (LR), 17.3 mm (CC) and 10.4 mm (AP) after bony-anatomy matching and 12.4 mm (LR), 11.4 mm (CC) and 9.7 mm (AP) after soft-tissue matching.

Conclusion

This study demonstrated that the implantation of gold markers was safe, albeit less stable compared to other marker types. Inter-fractional motion was largest cranio-caudally for markers in the distal oesophagus, which was reduced after soft-tissue compared to bony-anatomy matching. The impact of intra-fractional baseline shifts on margin calculation was rather small.

Comparative Dosimetric Analysis and Normal Tissue Complication Probability Modelling of Four-Dimensional Computed Tomography Planning Scans Within the UK NeoSCOPE Trial

AIMS

NeoSCOPE is a trial of two different neoadjuvant chemoradiotherapy regimens for resectable oesophageal cancer and was the first multicentre trial in the UK to incorporate four-dimensional computed tomography (4D-CT) into radiotherapy planning. Despite 4D-CT being increasingly accepted as a standard of care for lower third and junctional oesophageal tumours, there is limited evidence of its benefit over standard three-dimensional computed tomography (3D-CT).

MATERIALS

Using NeoSCOPE 4D-CT cases, we undertook a dosimetric comparison study of 3D-CT versus 4D-CT plans comparing target volume coverage and dose to organs at risk. We used established normal tissue complication probability models to evaluate the potential toxicity reduction of using 4D-CT plans in oesophageal cancer.

RESULTS

4D-CT resulted in a smaller median absolute PTV volume and lower dose levels for all reported constraints with comparable target volume coverage. NTCP modelling suggests a significant relative risk reduction of cardiac and pulmonary toxicity endpoints with 4D-CT.

CONCLUSION

Our work shows that incorporating 4D-CT into treatment planning may significantly reduce the toxicity burden from this treatment.

Impact of Esophageal Motion on Dosimetry and Toxicity With Thoracic Radiation Therapy

Purpose:

To investigate the impact of intra- and inter-fractional esophageal motion on dosimetry and observed toxicity in a phase I dose escalation study of accelerated radiotherapy with concurrent chemotherapy for locally advanced lung cancer.

Methods and Materials:

Patients underwent computed tomography imaging for radiotherapy treatment planning (CT1 and 4DCT1) and at 2 weeks (CT2 and 4DCT2) and 5 weeks (CT3 and 4DCT3) after initiating treatment. Each computed tomography scan consisted of 10-phase 4DCTs in addition to a static free-breathing or breath-hold computed tomography. The esophagus was independently contoured on all computed tomographies and 4DCTs. Both CT2 and CT3 were rigidly registered with CT1 and doses were recalculated using the original intensity-modulated radiation therapy plan based on CT1 to assess the impact of interfractional motion on esophageal dosimetry. Similarly, 4DCT1 data sets were rigidly registered with CT1 to assess the impact of intrafractional motion. The motion was characterized based on the statistical analysis of slice-by-slice center shifts (after registration) for the upper, middle, and lower esophageal regions, respectively. For the dosimetric analysis, the following quantities were calculated and assessed for correlation with toxicity grade: the percent volumes of esophagus that received at least 20 Gy (V20) and 60 Gy (V60), maximum esophageal dose, equivalent uniform dose, and normal tissue complication probability.

Results:

The interfractional center shifts were 4.4 ± 1.7 mm, 5.5 ± 2.0 mm and 4.9 ± 2.1 mm for the upper, middle, and lower esophageal regions, respectively, while the intrafractional center shifts were 0.6 ± 0.4 mm, 0.7 ± 0.7 mm, and 0.9 ± 0.7 mm, respectively. The mean V60 (and corresponding normal tissue complication probability) values estimated from the interfractional motion analysis were 7.8% (10%), 4.6% (7.5%), 7.5% (8.6%), and 31% (26%) for grade 0, grade 1, grade 2, and grade 3 toxicities, respectively.

Conclusions:

Interfractional esophageal motion is significantly larger than intrafractional motion. The mean values of V60 and corresponding normal tissue complication probability, incorporating interfractional esophageal motion, correlated positively with esophageal toxicity grade.

Tumour volume comparison between 16-row multi-detector computed tomography and 320-row area-detector computed tomography in patients with small lung tumours treated with stereotactic body radiotherapy: Effect of respiratory motion

PURPOSE

We compared image quality and volume of a moving simulated tumour and of lung tumours in patients who were treated with stereotactic body radiotherapy (SBRT) in a 16-row multi-detector CT (MDCT) versus a 320-row area-detector CT (ADCT). Tumour volumes in each respiratory phase were also evaluated.

MATERIALS AND METHODS

We acquired static and four-dimensional CT (4DCT) images of a moving phantom with 10- and 30-mm amplitudes with three periods of patterns (2, 4, and 6 s). Breath-hold and 4DCT images were acquired for 12 lung tumour patients who underwent SBRT. Image data were acquired via MDCT and ADCT. The tumours were delineated in each respiratory phase and their volumes in end-expiratory/end-inspiratory phase and mid-respiratory phase were compared.

RESULTS

In the phantom study, tumour volumes were smaller and closer to the static image when evaluated by ADCT than by MDCT. In the clinical study, average tumour volumes ± standard deviations were 9.58 ± 1.07 cm³ with MDCT (2.5-mm slice), and 7.12 ± 0.23 cm³ with ADCT (p < 0.01). Tumour volumes were closer to that of the breath hold CT in all patients evaluated by ADCT than by MDCT. Unlike MDCT, tumour volumes acquired by ADCT were smaller in end-expiratory or end-inspiratory phase than in the mid-respiratory phase.

CONCLUSIONS

Tumour volumes in each of the respiratory phases in ADCT were significantly smaller and closer to the static image than the corresponding volumes in MDCT. This suggests that treated volume can be reduced if ADCT is used in treatment planning.

Dosimetric Benefits of Midposition Compared With Internal Target Volume Strategy for Esophageal Cancer Radiation Therapy

PURPOSE

Both midposition (MidP) and internal target volume (ITV) strategies can take the respiration-induced target motion into account. This study aimed to compare these 2 strategies in terms of clinical target volume (CTV) coverage and dose to organs at risk (OARs) for esophageal cancer radiation therapy (RT).

METHODS AND MATERIALS

Fifteen patients with esophageal cancer were included retrospectively for neoadjuvant RT planning. Per patient, a 10-phase, 4-dimensional (4D) computed tomography (CT) scan (4D-CT) was acquired with CTV and OARs delineated on the 20% phase. The MidP-CT scan was reconstructed based on deformable image registration between the 20% phase and the other 9 phases; thereby, the CTV and OARs delineations were propagated and an ITV was constructed. Both MidP and ITV strategies were used for treatment planning, yielding the planned dose. Next, these plans were applied to the 10-phase 4D-CT to calculate the dose distribution for each phase of the 4D-CT. On the basis of the deformable image registration, these calculated dose distributions were warped and averaged to yield the accumulated 4D dose. Subsequently, we compared, in terms of CTV coverage and dose to OARs, the planned dose with the accumulated 4D dose and the MidP strategy with the ITV strategy.

RESULTS

The differences between the planned dose and the accumulated 4D dose were limited and clinically irrelevant. In 14 patients, both MidP and ITV strategies showed V_95% > 98% for the CTV. Compared with the ITV strategy, the MidP strategy showed a significant reduction of approximately 10% in the dose-volume histogram parameters for the lungs, heart, and liver (P < .001, Wilcoxon signed-rank test).

CONCLUSIONS

Compared with the ITV strategy, the MidP strategy in treatment planning can lead to a reduction of approximately 10% in the dose to OARs, with an adequate CTV coverage for esophageal cancer RT.

Intrafraction esophageal motion in patients with clinical T1N0 esophageal cancer

Aim

To investigate the intrafraction movement of the esophagus using fiducial markers.

Background

Studies on intrafraction esophageal motion using the fiducial markers are scarce.

Materials and methods

We retrospectively analyzed patients with clinical T1N0 esophageal cancer who had received fiducial markers at our hospital between July 2007 and December 2013. Real-Time Position Management System to track the patient's respiration was used, and each patient underwent three-dimensional computed tomography of the resting expiratory and inspiratory level. We used the center of the marker to calculate the distance between the expiratory and inspiratory breath-holds, which were measured with the radiotherapy treatment planning system in three directions: left-right (LR), superior-inferior (SI), and anterior-posterior (AP). The movements at each site were compared with the Kruskal-Wallis analysis and Wilcoxon rank sum test with a Bonferroni correction.

Results

A total of 101 patients with 201 fiducial markers were included. The upper, middle and lower thoracic positions had 40, 77, and 84 markers, respectively. The mean absolute magnitudes of the shifts (standard deviation) were 0.18 (0.19) cm, 0.68 (0.46) cm, and 0.24 (0.24) cm in the LR, SI, and AP directions, respectively. From the cumulative frequency distribution, we assumed that 0.35 cm LR, 0.8 cm SI, and 0.3 cm AP in the upper; 0.5 cm LR, 1.55 cm SI, and 0.55 cm AP in the middle; and 0.75 cm LR, 1.9 cm SI, and 0.95 cm AP in the lower thoracic esophagus covered 95% of the cases.

Conclusions

The internal margin based on the site of esophagus was estimated.

Quantifying esophageal motion during free-breathing and breath-hold using fiducial markers in patients with early-stage esophageal cancer

Introduction

Cardiac toxicity after definitive chemoradiotherapy for esophageal cancer is a critical issue. To reduce irradiation doses to organs at risk, individual internal margins need to be identified and minimized. The purpose of this study was to quantify esophageal motion using fiducial makers based on four-dimensional computed tomography, and to evaluate the inter-CBCT session marker displacement using breath-hold.

Materials and methods

Sixteen patients with early stage esophageal cancer, who received endoscopy-guided metallic marker placement for treatment planning, were included; there were 35 markers in total, with 9, 15, and 11 markers in the upper thoracic, middle thoracic, and lower thoracic/esophagogastric junction regions, respectively. We defined fiducial marker motion as motion of the centroidal point of the markers. Respiratory esophageal motion during free-breathing was defined as the amplitude of individual marker motion between the consecutive breathing and end-expiration phases, derived from four-dimensional computed tomography. The inter-CBCT session marker displacement using breath-hold was defined as the amplitudes of marker motion between the first and each cone beam computed tomography image. Marker motion was analyzed in the three regions (upper thoracic, middle thoracic, and lower thoracic/esophagogastric junction) and in three orthogonal directions (right-left; anterior-posterior; and superior-inferior).

Results

Respiratory esophageal motion during free-breathing resulted in median absolute maximum amplitudes (interquartile range), in right-left, anterior-posterior, and superior-inferior directions, of 1.7 (1.4) mm, 2.0 (1.5) mm, and 3.6 (4.1) mm, respectively, in the upper thoracic region, 0.8 (1.1) mm, 1.4 (1.2) mm, and 4.8 (3.6) mm, respectively, in the middle thoracic region, and 1.8 (0.8) mm, 1.9 (2.0) mm, and 8.0 (4.5) mm, respectively, in the lower thoracic/esophagogastric region. The inter-CBCT session marker displacement using breath-hold resulted in median absolute maximum amplitudes (interquartile range), in right-left, anterior–posterior, and superior-inferior directions, of 1.3 (1.0) mm, 1.1 (0.7) mm, and 3.3 (1.8) mm, respectively, in the upper thoracic region, 0.7 (0.7) mm, 1.1 (0.4) mm, and 3.4 (1.4) mm, respectively, in the middle thoracic region, and 2.0 (0.8) mm, 2.6 (2.2) mm, and 3.5 (1.8) mm, respectively, in the lower thoracic/esophagogastric region.

Conclusions

During free-breathing, esophageal motion in the superior-inferior direction in all sites was large, compared to the other directions, and amplitudes showed substantial inter-individual variability. The breath-hold technique is feasible for minimizing esophageal displacement during radiotherapy in patients with esophageal cancer.

Tumour motion of oesophageal squamous cell carcinoma evaluated by cine MRI: associated with tumour location

AIM

To evaluate the association between oesophageal tumour motion and tumour location using cine magnetic resonance imaging (MRI).

MATERIALS AND METHODS

Thirty-three consecutive patients with oesophageal squamous cell carcinoma were enrolled, and underwent cine MRI of oesophageal tumours. The maximum displacements in the anterior-posterior (A-P), superior-inferior (S-I), and left-right (L-R) directions of the tumours were assessed statistically to show their associations with tumour location.

RESULTS

Tumour motion in A-P and S-I directions increased from upper to lower oesophagus (r=0.505, p=0.003; and r=0.600, p<0.001, respectively). In A-P and S-I directions, tumours showed larger motion in the lower oesophagus than in the upper or middle oesophagus (all p<0.05). Motion of middle and lower oesophageal tumours in the S-I direction was larger than in L-R or A-P direction (all p<0.05). To provide 95% geometric coverage for the motion of upper oesophageal tumours, statistical analysis showed margins of 3.75 mm in L-R direction, 3.72 mm in A-P direction, and 5.38 mm in S-I direction. For the motion of tumours of the middle oesophagus, 95% coverage required margins of 8.50, 6.62, and 11.96 mm in L-R, A-P, and S-I directions, respectively, and for lower oesophageal tumours, 95% coverage required margins of 9.17, 9.68, and 12.98 mm in L-R, A-P, and S-I direction, respectively.

CONCLUSION

Oesophageal tumour motion in different directions can be associated with tumour location as shown on cine MRI, suggesting that the present findings could be helpful for better understanding oesophageal tumour motion and gating individualised radiation delivery strategies.

Fiducial markers coupled with 3D PET/CT offer more accurate radiation treatment delivery for locally advanced esophageal cancer

BACKGROUND AND AIMS

 The role of three-dimensional positron emission tomography/computed tomography (3 D PET/CT) in esophageal tumors that move with respiration and have potential for significant mucosal inflammation is unclear. The aim of this study was to determine the correlation between gross tumor volumes derived from 3 D PET/CT and endoscopically placed fiducial markers.

METHODS

 This was a retrospective, IRB approved analysis of 40 patients with esophageal cancer with fiducials implanted and PET/CT. The centroid of each fiducial was identified on PET/CT images. Distance between tumor volume and fiducials was measured using axial slices. Image features were extracted and tested for pathologic response predictability.

RESULTS

 The median adaptively calculated threshold value of the standardized uptake value (SUV) to define the metabolic tumor volume (MTV) border was 2.50, which corresponded to a median 23 % of the maximum SUV. The median distance between the inferior fiducial centroid and MTV was - 0.60 cm (- 3.9 to 2.7 cm). The median distance between the superior fiducial centroid and MTV was 1.25 cm (- 4.2 to 6.9 cm). There was no correlation between MTV-to-fiducial distances greater than 2 cm and the gastroenterologist who performed the fiducial implantation. Eccentricity demonstrated statistically significant correlations with pathologic response.

CONCLUSIONS

 There was a stronger correlation between inferior fiducial location and MTV border compared to the superior extent. The etiology of the discordance superiorly is unclear, potentially representing benign secondary esophagitis, presence of malignant nodes, inflammation caused by technical aspects of the fiducial placement itself, or potential submucosal disease. Given the concordance inferiorly and the ability to more precisely set up the patient with daily image guidance matching to fiducials, it may be possible to minimize the planning tumor volume (PTV) margin in select patients, thereby, limiting dose to normal structures.

Recent advances in intensity modulated radiotherapy and proton therapy for esophageal cancer

INTRODUCTION

Radiotherapy is an important component of the standard of care for esophageal cancer. In the past decades, significant improvements in the planning and delivery of radiation techniques have led to better dose conformity to the target volume and improved normal tissue sparing. Areas covered: This review focuses on the advances in radiotherapy techniques and summarizes the availably dosimetric and clinical outcomes of intensity-modulated radiation therapy (IMRT), volumetric modulated arc therapy, proton therapy, and four-dimensional radiotherapy for esophageal cancer, and discusses the challenges and future development of proton therapy. Expert commentary: Although three-dimensional conformal radiotherapy is the standard radiotherapy technique in esophageal cancer, the retrospectively comparative studies strongly suggest that the dosimetric advantage of IMRT over three-dimensional conformal radiotherapy can translate into improved clinical outcomes, despite the lack of prospective randomized evidence. As a novel form of conventional IMRT technique, volumetric modulated arc therapy can produce equivalent or superior dosimetric quality with significantly higher treatment efficiency in esophageal cancer. Compared with photon therapy, proton therapy has the potential to achieve further clinical improvement due to their physical properties; however, prospective clinical data, long-term results, and cost-effectiveness are needed.

Parietal pleural invasion/adhesion of subpleural lung cancer: Quantitative 4-dimensional CT analysis using dynamic-ventilatory scanning

PURPOSE

Using 4-dimensional dynamic-ventilatory scanning by a 320-row computed tomography (CT) scanner, we performed a quantitative assessment of parietal pleural invasion and adhesion by peripheral (subpleural) lung cancers.

METHODS

Sixteen patients with subpleural lung cancer underwent dynamic-ventilation CT during free breathing. Neither parietal pleural invasion nor adhesion was subsequently confirmed by surgery in 10 patients, whereas the other 6 patients were judged to have parietal pleural invasion or adhesion. Using research software, we tracked the movements of the cancer and of an adjacent structure such as the rib or aorta, and converted the data to 3-dimensional loci. The following quantitative indices were compared by the Mann-Whitney test: cross-correlation coefficient between time curves for the distances moved from the inspiratory frame by the cancer and the adjacent structure, the ratio of the total movement distances (cancer/adjacent structure), and the cosine similarities between the inspiratory and expiratory vectors (from the cancer to the adjacent structure) and between vectors of the cancer and of the adjacent structure (from inspiratory to expiratory frames).

RESULTS

Generally, the movements of the loci of the lung cancer and the adjacent structure were similar in patients with parietal pleural invasion/adhesion, while they were independent in patients without. There were significant differences in all the parameters between the two patient groups (cross-correlation coefficient and the movement distance ratio, P<0.01; cosine similarities, P<0.05).

CONCLUSION

These observations suggest that quantitative indices by dynamic-ventilation CT can be utilized as a novel imaging approach for the preoperative assessment of parietal pleural invasion/adhesion.

Intrafractional dose variation and beam configuration in carbon ion radiotherapy for esophageal cancer

Background

In carbon ion radiotherapy (CIR) for esophageal cancer, organ and target motion is a major challenge for treatment planning due to potential range deviations. This study intends to analyze the impact of intrafractional variations on dosimetric parameters and to identify favourable settings for robust treatment plans.

Methods

We contoured esophageal boost volumes in different organ localizations for four patients and calculated CIR-plans with 13 different beam geometries on a free-breathing CT. Forward calculation of these plans was performed on 4D-CT datasets representing seven different phases of the breathing cycle. Plan quality was assessed for each patient and beam configuration.

Results

Target volume coverage was adequate for all settings in the baseline CIR-plans (V₉₅ > 98% for two-beam geometries, > 94% for one-beam geometries), but reduced on 4D-CT plans (V₉₅ range 50–95%). Sparing of the organs at risk (OAR) was adequate, but range deviations during the breathing cycle partly caused critical, maximum doses to spinal cord up to 3.5x higher than expected. There was at least one beam configuration for each patient with appropriate plan quality.

Conclusions

Despite intrafractional motion, CIR for esophageal cancer is possible with robust treatment plans when an individually optimized beam setup is selected depending on tumor size and localization.

Esophageal motion characteristics in thoracic esophageal cancer: Impact of clinical stage T4 versus stages T1-T3

PURPOSE

The main purpose was to investigate the differences of the esophageal motion (EM) and the internal target volume (ITV) margins for the esophagus between clinical T1-T3 (cT1-T3) and cT4 cases, using 4-dimensional computed tomography. A secondary purpose was to assess the metastatic lymph nodal motion (NM) and the ITV margins for lymph nodes (LNs) using the datasets of patients with nodal involvement pathologically defined.

METHODS AND MATERIALS

We analyzed patients with thoracic esophageal cancer consecutively treated with definitive chemoradiation, measuring the EM and the ITV margins in the left-right, anteroposterior, and superoinferior directions. All esophageal contours were divided at the carina. The EM and NM were measured from the displacement of the centroid point between 0% images (at the end of inhalation) and 50% images (at the end of exhalation). The ITV margins were defined as the maximum distance in each direction from the clinical target volume at the 4-dimensional computed tomography average images to the intersection of the clinical target volume at the 0% and 50% images of complete coverage in each patient.

RESULTS

The EM below the carina in cT4 was significantly smaller than that in cT1-T2 in all directions (P < .01) and than that in cT3 in all directions (left-right: P = .03, anteroposterior and superoinferior: P < .01). The EM in the case of a cT4 tumor located below the carina was smaller than that in the case of cT4 tumor located above the carina. The NM of abdominal-LNs was much larger than that of cervicothoracic-LNs and the EM below the carina. These tendencies were similar in the ITV measurements.

CONCLUSIONS

The EM and the ITV margins in cT4 were significantly smaller than those in cT1-T3. The NM and the ITV margins of abdominal LNs were much larger than those of cervicothoracic LNs and the esophagus. In clinical radiation therapy planning for esophageal cancer, we should take cT stage into consideration.

Comparison of planning target volumes based on three-dimensional and four-dimensional CT imaging of thoracic esophageal cancer

Background and purpose

To investigate the definition of planning target volumes (PTVs) based on four-dimensional computed tomography (4DCT) compared with conventional PTV definition and PTV definition using asymmetrical margins for thoracic primary esophageal cancer.

Materials and methods

Forty-three patients with esophageal cancer underwent 3DCT and 4DCT simulation scans during free breathing. The motions of primary tumors located in the proximal (group A), middle (group B), and distal (group C) thoracic esophagus were obtained from the 4DCT scans. PTV_3D was defined on 3DCT using the tumor motion measured based on 4DCT, PTV conventional (PTV_conv) was defined on 3DCT by adding a 1.0 cm margin to the clinical target volume, and PTV_4D was defined as the union of the target volumes contoured on the ten phases of the 4DCT images. The centroid positions, volumetric differences, and dice similarity coefficients were evaluated for all PTVs.

Results

The median centroid shifts between PTV_3D and PTV_4D and between PTV_conv and PTV_4D in all three dimensions were <0.3 cm for the three groups. The median size ratios of PTV_4D to PTV_3D were 0.80, 0.88, and 0.71, and PTV_4D to PTV_conv were 0.67, 0.73, and 0.76 (χ²=−3.18, −2.98, and −3.06; P=0.001, 0.003, and 0.002) for groups A, B, and C, respectively. The dice similarity coefficients were 0.87, 0.90, and 0.81 between PTV_4D and PTV_3D and 0.80, 0.84, and 0.83 between PTV_4D and PTV_conv (χ² =−3.18, −2.98, and −3.06; P=0.001, 0.003, and 0.002) for groups A, B, and C, respectively. The difference between the degree of inclusion of PTV_4D in PTV_3D and that of PTV_4D in PTV_conv was <2% for all groups. Compared with PTV_conv, the amount of irradiated normal tissue for PTV_3D was decreased by 11.81% and 11.86% in groups A and B, respectively, but was increased by 2.93% in group C.

Conclusion

For proximal and middle esophageal cancer, 3DCT-based PTV using asymmetrical margins provides good coverage of PTV_4D; however, for distal esophageal cancer, 3DCT-based PTV using conventional margins provides ideal conformity with PTV_4D.

Correlation of primary middle and distal esophageal cancers motion with surrounding tissues using four-dimensional computed tomography

Purpose

To investigate the correlation of gross tumor volume (GTV) motion with the structure of interest (SOI) motion and volume variation for middle and distal esophageal cancers using four-dimensional computed tomography (4DCT).

Patients and methods

Thirty-three patients with middle or distal esophageal carcinoma underwent 4DCT simulation scan during free breathing. All image sets were registered with 0% phase, and the GTV, apex of diaphragm, lung, and heart were delineated on each phase of the 4DCT data. The position of GTV and SOI was identified in all 4DCT phases, and the volume of lung and heart was also achieved. The phase relationship between the GTV and SOI was estimated through Pearson’s correlation test.

Results

The mean peak-to-peak displacement of all primary tumors in the lateral (LR), anteroposterior (AP), and superoinferior (SI) directions was 0.13 cm, 0.20 cm, and 0.30 cm, respectively. The SI peak-to-peak motion of the GTV was defined as the greatest magnitude of motion. The displacement of GTV correlated well with heart in three dimensions and significantly associated with bilateral lung in LR and SI directions. A significant correlation was found between the GTV and apex of the diaphragm in SI direction (r_left=0.918 and r_right=0.928). A significant inverse correlation was found between GTV motion and varying lung volume, but the correlation was not significant with heart (r_LR=−0.530, r_AP=−0.531, and r_SI=−0.588) during respiratory cycle.

Conclusion

For middle and distal esophageal cancers, GTV should expand asymmetric internal margins. The primary tumor motion has quite good correlation with diaphragm, heart, and lung.

Differences in displacement of the proximal and distal ends of mid-upper thoracic esophageal squamous cell carcinoma

In the present study, clips were used as markers to evaluate displacement differences between proximal and distal ends of esophageal tumors and to test whether their internal target volume (ITV) margins should be determined separately. A total of 23 patients with mid-upper thoracic esophageal squamous-cell carcinoma, a tumor length of ≤8 cm and an esophageal lumen suitable for endoscopic ultrasonography were recruited for the present study. Clips were implanted endoscopically at the proximal and distal ends of the esophageal tumor (upper and lower clips). In a further exploratory study on 16 of the patients, a third clip was placed at the distal esophagus 2 cm above the gastro-esophageal junction (GEJ) (cardiac clip). The clips were contoured for all 10 phases of the four-dimensional computed tomography and the maximum displacements of the clip centroids among different breathing phases in left-right (LR), superior-inferior (SI) and anterior-posterior (AP) directions were marked as x, y and z, respectively. The ITV margins that covered 95% of the LR, SI and AP motion were 2.89, 5.00 and 2.36 mm, respectively. Axial displacement (y) was greater than radial displacement (x, z; P<0.05). It was also revealed that LR(x), SI(y) and AP(z) displacement of cardiac clips was greater than that of upper or lower clips (P<0.05). Differences in the axial and radial displacement of the upper and lower clips indicated that axial and radial ITV margins should be determined separately. However, further study is required on patients in whom the distal tumor end is located in proximity to the GEJ.

Effect of contrast enhancement in delineating GTV and constructing IGTV of thoracic oesophageal cancer based on 4D-CT scans

OBJECTIVE

To investigate the effect of contrast enhancement on delineating the gross tumour volumes (GTVs) of different respiratory phases and constructing the corresponding internal GTVs (IGTVs) of primary thoracic oesophageal cancer based on four-dimensional computed tomography (4D-CT) scans.

METHODS

Forty-five patients with upper (14 cases), middle (16 cases), or lower (15 cases) thoracic oesophageal cancer sequentially underwent conventional plain and contrast-enhanced 4D-CT scans during free breathing. First, the GTVs were delineated on plain 4D-CT, and the corresponding IGTVs were constructed by a physician. Then the GTVs were delineated on contrast-enhanced 4D-CT images, and the corresponding IGTVs were constructed by the same physician using the same standards.

RESULTS

The coefficient of variation for the target volume delineated on contrast-enhanced 4D-CT images was constantly smaller than that for plain 4D-CT images. The length of the GTVs along the z axis, as well as the volumes of the GTVs that were delineated and the IGTVs that were constructed, did not change between contrast-enhanced and plain 4D-CT images in patients with upper or lower thoracic oesophageal cancer (P>0.05), but showed significant differences in patients with middle thoracic oesophageal cancer (P<0.05).

CONCLUSIONS

Contrast-enhanced 4D-CT scans can reduce the error of target volume delineation and be used to construct a more accurate internal target volume in patients with middle thoracic oesophageal cancer, however, whether GTV delineation or IGTV construction for patients with upper or lower thoracic oesophageal cancer, no significant benefit was found from contrast-enhanced 4D-CT scan.

Efficacy and feasibility of ambulatory treatment-based monthly nedaplatin plus S-1 in definitive or salvage concurrent chemoradiotherapy for early, advanced, and relapsed esophageal cancer

BACKGROUND

Standard chemoradiotherapy (CRT) using cisplatin (CDDP) and 5-fluorouracil (5-FU) is an optional treatment for patients with stage II-III esophageal cancer. However, there are some demerits in this regimen because CDDP administration requires a large transfusion volume and 5-FU must be continuously infused over 24 h. Therefore, hospitalization is unavoidable. We collected retrospectively the data of definitive CRT with nedaplatin and S-1 as carried out in our institution.

METHODS

Patients with early and advanced esophageal cancer and relapsed esophageal cancer after radical surgery were included. Nedaplatin 80 mg/m(2) was given on days 1 and 29, and S-1 80 mg/m(2) on days 1-14 and 29-42. No prophylactic treatment with granulocyte colony stimulating factor was administered. Patients received two courses of concurrent radiotherapy of more than 50 Gy with or without two additional courses as adjuvant therapy every 4 weeks.

RESULTS

Between August 2011 and June 2015, 89 patients (age range, 44-86 years; K-PS 90-100, 81 %; squamous cell carcinoma histology, 97 %; definitive/salvage CRT, 75/25 %) were collected. Twenty-one (24 %) patients completed four cycles, and 94 % received two or more cycles. Grade 4 leukopenia, thrombocytopenia, and anemia occurred in 12, 7, and 10 % of the patients, respectively. Five patients developed febrile neutropenia. Grade 3 non-hematological toxicity included infection in 12 %, mucositis/esophagitis in 3 %, kidney in 3 %, and fatigue in 3 %. Sixty-four patients (72 %) received the prescribed full dose and full cycles of chemotherapy. A complete response was achieved in 76 patients (85 %). The 3-year overall survival rate was 54.4 % in definitive CRT and 39.8 % in salvage CRT, respectively. Sixty-two subjects (70 %) received treatment as outpatients.

CONCLUSIONS

Nedaplatin and S-1 in combination with radiotherapy is feasible, and toxicity is tolerable. This treatment method has the potential to shorten hospitalization without impairing the efficacy of CRT.

Marker-based quantification of interfractional tumor position variation and the use of markers for setup verification in radiation therapy for esophageal cancer

PURPOSE

The aim of this study was to quantify interfractional esophageal tumor position variation using markers and investigate the use of markers for setup verification.

MATERIALS AND METHODS

Sixty-five markers placed in the tumor volumes of 24 esophageal cancer patients were identified in computed tomography (CT) and follow-up cone-beam CT. For each patient we calculated pairwise distances between markers over time to evaluate geometric tumor volume variation. We then quantified marker displacements relative to bony anatomy and estimated the variation of systematic (Σ) and random errors (σ). During bony anatomy-based setup verification, we visually inspected whether the markers were inside the planning target volume (PTV) and attempted marker-based registration.

RESULTS

Minor time trends with substantial fluctuations in pairwise distances implied tissue deformation. Overall, Σ(σ) in the left-right/cranial-caudal/anterior-posterior direction was 2.9(2.4)/4.1(2.4)/2.2(1.8) mm; for the proximal stomach, it was 5.4(4.3)/4.9(3.2)/1.9(2.4) mm. After bony anatomy-based setup correction, all markers were inside the PTV. However, due to large tissue deformation, marker-based registration was not feasible.

CONCLUSIONS

Generally, the interfractional position variation of esophageal tumors is more pronounced in the cranial-caudal direction and in the proximal stomach. Currently, marker-based setup verification is not feasible for clinical routine use, but markers can facilitate the setup verification by inspecting whether the PTV covers the tumor volume adequately.

Implications of free breathing motion assessed by 4D-computed tomography on the delivered dose in radiotherapy for esophageal cancer

The aim of this study was to assess the effect of breathing motion on the delivered dose in esophageal cancer 3-dimensional (3D)-conformal radiotherapy (3D-CRT), intensity-modulated radiotherapy (IMRT), and volumetric modulated arc therapy (VMAT). We assessed 16 patients with esophageal cancer. All patients underwent 4D-computed tomography (4D-CT) for treatment planning. For each of the analyzed patients, 1 3D-CRT, 1 IMRT, and 1 VMAT (RapidArc-RA) plan were calculated. Each of the 3 initial plans was recalculated on the 4D-CT (for the maximum free inspiration and maximum free expiration) to assess the effect of breathing motion. We assessed the minimum dose (Dmin) and mean dose (Dmean) to the esophagus within the planning target volume, the volume changes of the lungs, the Dmean and the total lung volume receiving at least 40Gy (V40), and the V30, V20, V10, and V5. For the heart we assessed the Dmean and the V25. Over all techniques and all patients the change in Dmean as compared with the planned Dmean (planning CT [PCT]) to the esophagus was 0.48% in maximum free inspiration (CT_insp) and 0.55% in maximum free expiration (CT_exp). The Dmin CT_insp change was 0.86% and CT_exp change was 0.89%. The Dmean change of the lungs (heart) was in CT_insp 1.95% (2.89%) and 3.88% (2.38%) in CT_exp. In all, 4 patients had a clinically relevant change of the dose (≥ 5% Dmean to the heart and the lungs) between inspiration and expiration. These patients had a very cranially or caudally situated tumor. There are no relevant differences in the delivered dose to the regions of interest among the 3 techniques. Breathing motion management could be considered to achieve a better sparing of the lungs or heart in patients with cranially or caudally situated tumors.

Tumour delineation in oesophageal cancer - A prospective study of delineation in PET and CT with and without endoscopically placed clip markers

PURPOSE

The objective was to analyse the value of F-18-fluorodesoxyglucose (FDG)-positron emission tomography/computed tomography (PET/CT) for delineation of the Gross Tumour Volumes (GTVs) in primary radiotherapy of oesophageal cancer.

METHOD

20 consecutive and prospective patients (13 men, 7 women) underwent FDG-PET/CT for initial staging and radiation treatment planning. After endoscopy-guided clipping of the tumour another CT study was acquired. The CT and the FDG-PET/CT were registered with a rigid and a non-rigid registration algorithm to compare the overlap between GTV contours defined with the following methods: manual GTV definition in (1) the CT image of the FDG-PET/CT, (2) the PET image of the FDG-PET/CT, (3) the CT study based on endoscopic clips (CT clip), and (4) in the PET-data using different semi-automatic PET segmentation algorithms including a gradient-based algorithm. The absolute tumour volumes, tumour length in cranio-caudal direction, as well as the overlap with the reference volume (CT-clip) were compared for all lesions and separately for proximal/distal tumours.

RESULTS

In 6 of the patients, FDG-PET/CT discovered previously unknown tumour locations, which resulted in either altered target volumes (n=3) or altered intent of treatment from curative to palliative (n=3) by upstaging to stage IV. For tumour segmentation a large variability between all algorithms was found. For the absolute tumour volumes with CT-clip as reference, no single PET-based segmentation algorithm performed better compared to using the manual CT delineation alone. The best correlation was found between the CT-clip and the gradient based segmentation algorithm (PET-edge, R(2)=0.84) as well as the manual CT-delineation (CT-manual R(2)=0.89). Non-rigid registration between CT and image FDG-PET/CT did not decrease variability between segmentation methods compared to rigid registration statistically significant. For the analysis of tumour length no homogeneous correlation was found.

CONCLUSION

Whereas FDG-PET was highly relevant for staging purposes, CT imaging with clipping of the tumour extension remains the gold standard for GTV delineation.

Dynamic tumor-tracking radiotherapy with real-time monitoring for liver tumors using a gimbal mounted linac

PURPOSE

Dynamic tumor-tracking stereotactic body radiotherapy (DTT-SBRT) for liver tumors with real-time monitoring was carried out using a gimbal-mounted linear accelerator and the efficacy of the system was determined. In addition, four-dimensional (4D) dose distribution, tumor-tracking accuracy, and tumor-marker positional variations were evaluated.

MATERIALS AND METHODS

A fiducial marker was implanted near the tumor prior to treatment planning. The prescription dose at the isocenter was 48-60 Gy, delivered in four or eight fractions. The 4D dose distributions were calculated with a Monte Carlo method and compared to the static SBRT plan. The intrafractional errors between the predicted target positions and the actual target positions were calculated.

RESULTS

Eleven lesions from ten patients were treated successfully. DTT-SBRT allowed an average 16% reduction in the mean liver dose compared to static SBRT, without altering the target dose. The average 95th percentiles of the intrafractional prediction errors were 1.1, 2.3, and 1.7 mm in the left-right, cranio-caudal, and anterior-posterior directions, respectively. After a median follow-up of 11 months, the local control rate was 90%.

CONCLUSIONS

Our early experience demonstrated the dose reductions in normal tissues and high accuracy in tumor tracking, with good local control using DTT-SBRT with real-time monitoring in the treatment of liver tumors.

Dosimetric evaluation of anatomical changes during treatment to identify criteria for adaptive radiotherapy in oesophageal cancer patients

BACKGROUND

Some oesophageal cancer patients undergoing chemotherapy and concomitant radiotherapy (chemoRT) show large interfractional anatomical changes during treatment. These changes may modify the dose delivered to the target and organs at risk (OARs). The aim of the presenwt study was to investigate the dosimetric consequences of anatomical changes during treatment to obtain criteria for an adaptive RT decision support system.

MATERIAL AND METHODS

Twenty-nine patients were treated with chemoRT for oesophageal and gastro-oesophageal junction cancer and set up according to daily cone beam computed tomography (CBCTs) scans. All patients had an additional replanning CT scan at median fraction number 10 (9-14), which was deformably registered to the original planning CT. Gross tumour volumes (GTVs), clinical target volumes (CTVs) and OARs were transferred to the additional CT and corrected by an exwperienced physician. Treatment plans were recalculated and dose to targets and OARs was evaluated. Treatment was adapted if the volume receiving 95% of the prescribed dose (V95%) coverage of CTV decreased > 1% or planning target volume (PTV) decreased by > 3%.

RESULTS

In total, nine adaptive events were observed: All nine were triggered by PTV V95% decrease > 3% [median 11% (5-41%)] and six of these were additionally triggered by CTV V95% decrease > 1% [median 5% (2-35%)]. The largest discrepancies were caused by interfractional baseline or amplitude shifts in diaphragm position (n = 5). Mediastinal (n = 6), oesophageal (n = 6) and bowel filling changes (n = 2) caused the remainder of the changes. For patients with dosimetric changes exceeding the adaptation limits, the discrepancies were confirmed by inspecting the daily CBCTs. In 31% of all patients, heart V30Gy increased more than 2% (maximum 5%). Only minor changes in lung dose or liver dose were seen.

CONCLUSION

Target coverage throughout the course of chemoRT treatment is compromised in some patients due to interfractional anatomical changes. Dose to the heart may increase as well.

The application of functional imaging techniques to personalise chemoradiotherapy in upper gastrointestinal malignancies

Functional imaging gives information about physiological heterogeneity in tumours. The utility of functional imaging tests in providing predictive and prognostic information after chemoradiotherapy for both oesophageal cancer and pancreatic cancer will be reviewed. The benefit of incorporating functional imaging into radiotherapy planning is also evaluated. In cancers of the upper gastrointestinal tract, the vast majority of functional imaging studies have used (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET). Few studies in locally advanced pancreatic cancer have investigated the utility of functional imaging in risk-stratifying patients or aiding target volume definition. Certain themes from the oesophageal data emerge, including the need for a multiparametric assessment of functional images and the added value of response assessment rather than relying on single time point measures. The sensitivity and specificity of FDG-PET to predict treatment response and survival are not currently high enough to inform treatment decisions. This suggests that a multimodal, multiparametric approach may be required. FDG-PET improves target volume definition in oesophageal cancer by improving the accuracy of tumour length definition and by improving the nodal staging of patients. The ideal functional imaging test would accurately identify patients who are unlikely to achieve a pathological complete response after chemoradiotherapy and would aid the delineation of a biological target volume that could be used for treatment intensification. The current limitations of published studies prevent integrating imaging-derived parameters into decision making on an individual patient basis. These limitations should inform future trial design in oesophageal and pancreatic cancers.

Reduced lung dose during radiotherapy for thoracic esophageal carcinoma: VMAT combined with active breathing control for moderate DIBH

Background

Lung radiation injury is a critical complication of radiotherapy (RT) for thoracic esophageal carcinoma (EC). Therefore, the goal of this study was to investigate the feasibility and dosimetric effects of reducing the lung tissue irradiation dose during RT for thoracic EC by applying volumetric modulated arc radiotherapy (VMAT) combined with active breathing control (ABC) for moderate deep inspiration breath-hold (mDIBH).

Methods

Fifteen patients with thoracic EC were randomly selected to undergo two series of computed tomography (CT) simulation scans with ABC used to achieve mDIBH (representing 80% of peak DIBH value) versus free breathing (FB). Gross tumor volumes were contoured on different CT images, and planning target volumes (PTVs) were obtained using different margins. For PTV_-FB, intensity-modulated radiotherapy (IMRT) was designed with seven fields, and VMAT included two whole arcs. For PTV_-DIBH, VMAT with three 135° arcs was applied, and the corresponding plans were named: IMRT_-FB, VMAT_-FB, and VMAT_-DIBH, respectively. Dosimetric differences between the different plans were compared.

Results

The heart volumes decreased by 19.85%, while total lung volume increased by 52.54% in mDIBH, compared to FB (p < 0.05). The mean conformality index values and homogeneity index values for VMAT_-DIBH (0.86, 1.07) were slightly worse than those for IMRT_-FB (0.90, 1.05) and VMAT_-FB (0.90, 1.06) (p > 0.05). Furthermore, compared to IMRT_-FB and VMAT_-FB, VMAT_-DIBH reduced the mean total lung dose by 18.64% and 17.84%, respectively (p < 0.05); moreover, the V₅, V₁₀, V₂₀, and V₃₀ values for IMRT_-FB and VMAT_-FB were reduced by 10.84% and 10.65% (p > 0.05), 12.5% and 20% (p < 0.05), 30.77% and 33.33% (p < 0.05), and 50.33% and 49.15% (p < 0.05), respectively. However, the heart dose-volume indices were similar between VMAT_-DIBH and VMAT_-FB which were lower than IMRT_-FB without being statistically significant (p > 0.05). The monitor units and treatment time of VMAT_-DIBH were also the lowest (p < 0.05).

Conclusions

VMAT combined with ABC to achieve mDIBH is a feasible approach for RT of thoracic EC. Furthermore, this method has the potential to effectively reduce lung dose in a shorter treatment time and with better targeting accuracy.

Quantification of esophageal tumor motion on cine-magnetic resonance imaging

PURPOSE

To quantify the movement of esophageal tumors noninvasively on cine-magnetic resonance imaging (MRI) by use of a semiautomatic method to visualize tumor movement directly throughout multiple breathing cycles.

METHODS AND MATERIALS

Thirty-six patients with esophageal tumors underwent MRI. Tumors were located in the upper (8), middle (7), and lower (21) esophagus. Cine-MR images were collected in the coronal and sagittal plane during 60 seconds at a rate of 2 Hz. An adaptive correlation filter was used to automatically track a previously marked reference point. Tumor movement was measured in the craniocaudal (CC), left-right (LR), and anteroposterior (AP) directions and its relationship along the longitudinal axis of the esophagus was investigated.

RESULTS

Tumor registration within the individual images was typically done at a millisecond time scale. The mean (SD) peak-to-peak displacements in the CC, AP, and LR directions were 13.3 (5.2) mm, 4.9 (2.5) mm, and 2.7 (1.2) mm, respectively. The bandwidth to cover 95% of excursions from the mean position (c95) was also calculated to exclude outliers caused by sporadic movements. The mean (SD) c95 values were 10.1 (3.8) mm, 3.7 (1.9) mm, and 2.0 (0.9) mm in the CC, AP, and LR dimensions. The end-exhale phase provided a stable position in the respiratory cycle, compared with more variety in the end-inhale phase. Furthermore, lower tumors showed more movement than did higher tumors in the CC and AP directions.

CONCLUSIONS

Intrafraction tumor movement was highly variable between patients. Tumor position proved the most stable during the respiratory cycle in the end-exhale phase. A better understanding of tumor motion makes it possible to individualize radiation delivery strategies accordingly. Cine-MRI is a successful noninvasive modality to analyze motion for this purpose in the future.

Detection of interfraction displacement and volume variance during radiotherapy of primary thoracic esophageal cancer based on repeated four-dimensional CT scans

Background

To investigate the interfraction displacement and volume variation of primary thoracic esophagus carcinoma with enhanced four-dimensional computed tomography (4DCT) scanning during fractionated radiotherapy.

Methods

4DCT data sets were acquired at the time of treatment simulation and every ten fraction for each of 32 patients throughout treatment. Scans were registered to baseline (simulation) 4DCT scans by using bony landmarks. The gross tumor volumes (GTVs) were delineated on each data set. Coordinates of the GTV centroids were acquired on each respiration phase. Distance between center of the GTV contour on the simulation scan and the centers on subsequent scans were used to assess interfraction displacement between fractions. Volumes were constructed using three approaches: The GTV delineated from the maximum intensity projection (MIP) was defined IGTV_MIP, all 10 GTVs were combined to form IGTV₁₀, GTV_mean was the average of all 10 phases of each GTV.

Results

Interfraction displacement in left-right (LR), anterior-posterior (AP), superior-inferior (SI) directions and 3D vector were 0.13 ± 0.09 cm, 0.16 ± 0.12 cm, 0.34 ± 0.26 cm and 0.43 ± 0.24 cm, respectively between the tenth fraction and simulation 4DCT scan. 0.14 ± 0.09 cm, 0.19 ± 0.16 cm, 0.45 ± 0.43 cm and 0.56 ± 0.40 cm in LR, AP, SI and 3D vector respectively between the twentieth fraction and simulation 4DCT scan. Displacement in SI direction was larger than LR and AP directions during treatment. For distal esophageal cancer, increased interfraction displacements were observed in SI direction and 3D vector (P = 0.002 and P = 0.001, respectively) during radiotherapy. The volume of GTV_mean, IGTV_MIP, and IGTV₁₀ decreased significantly at the twentieth fraction for middle (median: 34.01%, 33.09% and 28.71%, respectively) and distal (median: 22.76%, 25.27% and 23.96%, respectively) esophageal cancer, but for the upper third, no significant variation were observed during radiotherapy.

Conclusions

Interfractional displacements in SI direction were larger than LR and AP directions. For distal location, significant changes were observed in SI direction and 3D vector during radiotherapy. For middle and distal locations, the best time to reset position should be selected at the twentieth fraction when the primary tumor target volume changed significantly, and it was preferable to guide target correction and planning modification.

Comparison of patient-specific internal gross tumor volume for radiation treatment of primary esophageal cancer based separately on three-dimensional and four-dimensional computed tomography images

To compare the target volume, position and matching index of the patient-specific internal gross tumor volume (IGTV) based on three-dimensional (3D) and four-dimensional (4D) computed tomography (CT) images for primary esophageal cancer. Twenty-nine patients with primary thoracic esophageal cancer underwent 3DCT and 4DCT scans during free breathing. IGTVs were constructed using three approaches: combining the gross target volumes from the 10 respiratory phases of the 4DCT dataset to produce IGTV10 ; IGTV2 was acquired by combining the two extreme phases; and IGTV3D was created from the 3DCT-based gross target volume by enlarging the 95th percentile of motion in each direction measured by the 4DCT. 0.16 cm lateral (LR), 0.14 cm anteroposterior (AP) and 0.29 cm superoinferior (SI) in the upper; 0.18 cm LR, 0.10 cm AP and 0.63 cm SI in the middle; and 0.40 cm LR, 0.58 cm AP and 0.82 cm in the lower thoracic esophagus could account for 95% of respiratory-induced tumor motion. The centroid position shift between IGTV10 and IGTV2 was all below 0.10 cm, and less than 0.20 cm between IGTV10 and IGTV3D . IGTV10 was bigger than IGTV2 ; the mean value of matching index for IGTV2 to IGTV10 was 0.87 ± 0.05, 0.85 ± 0.06 and 0.83 ± 0.05 for upper, middle and distal thoracic esophageal tumors, respectively, and just 0.57 ± 0.11, 0.56 ± 0.13 and 0.40 ± 0.03 between IGTV3D and IGTV10 . 4DCT-based IGTV10 is a reasonable patient-specific IGTV for primary thoracic esophageal cancer, and IGTV2 is considered as an acceptable alternative to IGTV10 . However, it seems unreasonable to use IGTV3D substitute IGTV10 .

Technical considerations in radiation therapy for gastroesophageal junction cancer

Contemporary randomized trials have demonstrated that radiation therapy combined with chemotherapy and surgery improves survival in both the neoadjuvant and adjuvant treatment of gastroesophageal cancers. Consequently, radiation treatment planning and administration have taken on an added importance to ensure optimal outcomes as well as minimize treatment-related morbidity. This article highlights recent technical advances and considerations for radiation therapy planning for gastroesophageal junction tumors.

Oesophageal Chemoradiotherapy in the UK--current practice and future directions

The SCOPE 1 trial closed to recruitment in early 2012 and has demonstrably improved the quality of UK radiotherapy. It has also shown that there is an enthusiastic upper gastrointestinal clinical oncology community that can successfully complete trials and deliver high-quality radiotherapy. Following on from SCOPE 1, this paper, authored by a consensus of leading UK upper gastrointestinal radiotherapy specialists, attempts to define current best practice and the questions to be answered by future clinical studies. The two main roles for chemoradiotherapy (CRT) in the management of potentially curable oesophageal cancer are definitive (dCRT) and neoadjuvant (naCRT). The rates of local failure after dCRT are consistently high, showing the need to evaluate more effective treatments, both in terms of optimal local and systemic therapeutic components. This will be the primary objective of the next planned UK dCRT trial and here we discuss the role of dose escalation and systemic therapeutic options that will form the basis of that trial. The publication of the Dutch 'CROSS' trial of naCRT has shown that this pre-operative approach can both be given safely and offer a significant survival benefit over surgery alone. This has led to the development of the UK NeoSCOPE trial, due to open in 2013. There will be a translational substudy to this trial and currently available data on the role of biomarkers in predicting response to therapy are discussed. Postoperative reporting of the pathology specimen is discussed, with recommendations for the NeoSCOPE trial. Both of these CRT approaches may benefit from recent developments, such as positron emission tomography/computed tomography and four-dimensional computed tomography for target volume delineation, planning techniques such as intensity-modulated radiotherapy and 'type b' algorithms and new treatment verification methods, such as cone-beam computed tomography. These are discussed here and recommendations made for their use.

Detection of esophageal fiducial marker displacement during radiation therapy with a 2-dimensional on-board imager: analysis of internal margin for esophageal cancer

PURPOSE

To quantify the interfraction displacement of esophageal fiducial markers for primary esophageal cancer radiation therapy.

METHODS AND MATERIALS

Orthogonal 2-dimensional (2D) matching records fused to vertebrae were analyzed in clinically staged T1/2N0 esophageal cancer patients undergoing endoscopic clipping as fiducial metal markers. Displacement of the markers between the digitally reconstructed radiographs and on-board kilovoltage images during radiation therapy was analyzed according to direction and esophageal site.

RESULTS

Forty-four patients, with 81 markers (10 proximal, 42 middle, and 29 distal), underwent 367 2D matching sessions during radiation therapy. The mean (SD) absolute marker displacement was 0.26 (0.30) cm in the right-left (RL), 0.50 (0.39) cm in the superior-inferior (SI), and 0.24 (0.21) cm in the anterior-posterior (AP) direction. Displacement was significantly larger in the SI than in the RL and AP directions (P<.0001). In the SI direction, mean absolute displacements of the distal, middle, and proximal esophagus were 0.67 (0.45) cm, 0.42 (0.32) cm, and 0.36 (0.30) cm, respectively. Distal esophagus displacement was significantly larger than those of the middle and proximal esophagus (P<.0001). The estimated internal margin to cover 95% of the cases was 0.75 cm in the RL and AP directions. In the SI direction, the margin was 1.25 cm for the proximal and middle esophagus and 1.75 cm for the distal esophagus.

CONCLUSIONS

The magnitude of interfraction displacement of esophageal clips was larger in the SI direction, particularly in the distal esophagus, but substantial displacement was observed in other directions and at other esophageal sites. It is practical to take estimated movements into account with internal margins, even if vertebrae-based 2D matching is performed.

Four-dimensional measurement of the displacement of metal clips or postoperative surgical staples during 320-multislice computed tomography scanning of gastric cancer

Purpose

To investigate the respiratory motion of metal clips or surgical staples placed in the gastric wall for planning of radiation therapy in gastric cancer patients.

Methods

This study examined 15 metal markers in the gastric walls of 12 patients with gastric cancer treated with external-beam photon RT. Motion assessment was analyzed in 41 respiratory phases covering 20 s acquired with computed tomography (CT) in the RT position using 320-multislice CT. The intra-fraction displacement was assessed in the cranio-caudal (CC), antero-posterior (AP), and right-left (RL) directions.

Results

Motion in the CC direction showed a very strong correlation (R² > 0.7) with the respiratory curve in all 15 markers. The mean (+/− SD) intra-fractional gastric motion (maximum range of displacement) was 12.5 (+/− 3.4) mm in the CC, 8.3 (+/− 2.2) mm in the AP, and 5.5 (+/− 3.0) mm in the RL direction. No significant differences in magnitude of motion were detected in the following: a) among the upper (n = 6), middle (n = 4), and lower (n = 5) stomach regions; b) between metal clips (n = 5) and surgical staples (n = 10); and c) between full (n = 9) and empty (n = 6) stomachs.

Conclusions

Motion in primary gastric tumor was evaluated with 320-multislice CT. According to this study, the 95th percentile values from the cumulative distributions of the RL, AP, and CC direction were 6.3 mm, 9.0 mm, and 13.6 mm, respectively.

The clinical application of 4D 18F-FDG PET/CT on gross tumor volume delineation for radiotherapy planning in esophageal squamous cell cancer

A combination of four-dimensional computed tomography with (18)F-fluorodeoxyglucose positron emission tomography (4D CT-FDG PET) was used to delineate gross tumor volume (GTV) in esophageal cancer (EC). Eighteen patients with EC were prospectively enrolled. Using 4D images taken during the respiratory cycle, the average CT image phase was fused with the average FDG PET phase in order to analyze the optimal standardized uptake values (SUV) or threshold. PET-based GTV (GTV(PET)) was determined with eight different threshold methods using the auto-contouring function on the PET workstation. The difference in volume ratio (VR) and conformality index (CI) between GTV(PET) and CT-based GTV (GTV(CT)) was investigated. The image sets via automatic co-registrations of 4D CT-FDG PET were available for 12 patients with 13 GTV(CT) values. The decision coefficient (R(2)) of tumor length difference at the threshold levels of SUV 2.5, SUV 20% and SUV 25% were 0.79, 0.65 and 0.54, respectively. The mean volume of GTV(CT) was 29.41 ± 19.14 ml. The mean VR ranged from 0.30 to 1.48. The optimal VR of 0.98, close to 1, was at SUV 20% or SUV 2.5. The mean CI ranged from 0.28 to 0.58. The best CI was at SUV 20% (0.58) or SUV 2.5 (0.57). The auto-contouring function of the SUV threshold has the potential to assist in contouring the GTV. The SUV threshold setting of SUV 20% or SUV 2.5 achieves the optimal correlation of tumor length, VR, and CI using 4D-PET/CT images.