A systematic review on the role of FDG-PET/CT in tumour delineation and radiotherapy planning in patients with esophageal cancer

Esophageal Radiography Interpretation: a Primer for the Gastroenterologist

PURPOSE OF REVIEW

Radiological studies can be helpful when evaluating patients with suspect esophageal disorders. From benign strictures to malignancy and motility disorders such as achalasia, imaging modalities play a significant role in diagnosis. This review explores the role of different imaging modalities in the most frequently encountered esophageal pathologies.

RECENT FINDINGS

Conventional barium esophagram has long been considered the primary imaging modality of the esophagus. In the same fashion, a timed barium esophagram is a valuable tool in the evaluation of achalasia and esophagogastric junction outlet obstruction. Over the last few decades there has been an increase in CT and MRI studies, which also play a role in the evaluation of esophageal pathologies. However, not infrequently, these newer imaging techniques can result in incidental esophageal findings. It is important that gastroenterologists appreciate the value of different modalities and recognize key imaging features. The diagnosis and management of esophageal disorders is evolving. A basic understanding of esophageal radiology is essential to any gastroenterologist caring for patients with esophageal complaints.

Esophageal cancer - the utility of PET/CT in staging prior to chemoradiation

Background

Thorough staging plays a significant role in determining therapy modality in esophageal cancer patients. The aim of this study was to assess whether positron emission tomography/computed tomography (PET/CT) may be safely omitted in selected groups of patients.

Materials and methods

This retrospective analysis included 37 esophageal cancer patients recruited to chemoradiation by the Multidisciplinary Tumor Board (MTB) at the Greater Poland Cancer Center in 2021. Prior to radiotherapy planning every patient was referred to PET/CT to have the extent of their disease assessed.

Results

Among 37 patients PET/CT changed the staging status to metastatic (M1) in six cases (3 planoepithelial and 3 adenocarcinomas). In all those cases but one (1 patient with supraclavicular node metastasis finally received chemoradiation) confirmation of distant metastases excluded patients from radical treatment. Interestingly, in the PET/CT distant positive group 3 patients were initially staged as locally advanced (without nodal involvement). The other 3 were initially identified as at least N2 in tomography.

Conclusion

Results of this report allowed the conclusion that PET/CT plays a key role in esophageal cancer patients considered for radical chemoradiation; therefore, it remains a necessary tool to exclude metastatic disease in both main pathology types. Since the delayed time for PET/CT scan in esophageal cancer patients planned to chemoradiation may negatively influence treatment results, the data should be alarming for national health provider.

The Prognostic Value of Sequential 18 F-FDG PET/CT Metabolic Parameters in Outcomes of Upper-Third Esophageal Squamous Cell Carcinoma Patients Treated with Definitive Chemoradiotherapy

Objective  The aim of this study is to determine prognostic values of sequential 18 F-FDG PET/CT metabolic parameters in locally advanced esophageal squamous cell carcinoma (ESCC) patients treated with definitive chemoradiotherapy. Materials and Methods  Forty locally advanced ESCC patients treated with definitive chemoradiotherapy (dCRT) who received pre-treatment 18 F-FDG PET/CT (PET1) and 3-months post-treatment 18 F-FDG PET/CT (PET2) were enrolled in the prospective study. 18 F-FDG PET parameters of the primary tumor including maximum and mean standardized uptake values (SUVmax, SUVmean), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) were calculated on PET delineated primary tumor. Using Kaplan-Meier curves to estimated overall survival (OS), progression-free survival (PFS), and local-regional control (LRC). Cox regression analysis was performed to find significant prognostic factors for survival. Results  With a median follow-up of 13.5 months, the 4-year OS, PFS, and LRC rates were 67.3%, 52.6%, and 53.4% respectively. Patients with MTV 2 > 5.7 had lower OS, PFS, and LRC rates than the lower MTV 2 group (p < 0.05). Univariate Cox regression analysis showed that MTV2 was a significant prognostic factor for OS, PFS, and LRC (p < 0.05). Conclusion  MTV parameter of sequential 18 F-FDG PET/CT could be used as a prognostic factor for OS, PFS, and LRC in locally advanced ESCC patients treated with dCRT.

Inter-Observer and Intra-Observer Variability in Gross Tumor Volume Delineation of Primary Esophageal Carcinomas Based on Different Combinations of Diagnostic Multimodal Images

Background and Purpose

This study aimed to investigate inter-/intra-observer delineation variability in GTVs of primary esophageal carcinomas (ECs) based on planning CT with reference to different combinations of diagnostic multimodal images from endoscopy/EUS, esophagography and FDG-PET/CT.

Materials and Methods

Fifty patients with pathologically proven thoracic EC who underwent diagnostic multimodal images before concurrent chemoradiotherapy were enrolled. Five radiation oncologist independently delineated the GTVs based on planning CT only (GTV_C), CT combined with endoscopy/EUS (GTV_CE), CT combined with endoscopy/EUS and esophagography (X-ray) (GTV_CEX), and CT combined with endoscopy/EUS, esophagography, and FDG-PET/CT (GTV_CEXP). The intra-/inter-observer variability in the volume, longitudinal length, generalized CI (CI_gen), and position of the GTVs were assessed.

Results

The intra-/inter-observer variability in the volume and longitudinal length of the GTVs showed no significant differences (p>0.05). The mean intra-observer CI_gen values for all observers was 0.73 ± 0.15. The mean inter-observer CI_gen values for the four multimodal image combinations was 0.67 ± 0.11. The inter-observer CI_gen for the four combined images was the largest, showing significant differences with those for the other three combinations. The intra-observer CI_gen among different observers and inter-observer CI_gen among different combinations of multimodal images showed significant differences (p<0.001). The intra-observer CI_gen for the senior radiotherapists was larger than that for the junior radiotherapists (p<0.001).

Conclusion

For radiation oncologists with advanced medical imaging training and clinical experience, using diagnostic multimodal images from endoscopy/EUS, esophagography, and FDG-PET/CT could reduce the intra-/inter-observer variability and increase the accuracy of target delineation in primary esophageal carcinomas.

Motion-compensated FDG PET/CT for oesophageal cancer

PURPOSE

Respiratory-induced motion of oesophageal tumours and lymph nodes can influence positron-emission tomography/computed tomography (PET/CT). The aim was to compare standard three-dimensional (3D) and motion-compensated PET/CT regarding standardized uptake value (SUV), metabolic tumour volume (MTV) and detection of lymph node metastases.

METHODS

This prospective observational study (NCT02424864) included 37 newly diagnosed oesophageal cancer patients. Diagnostic PET/CT was reconstructed in 3D and motion-compensated PET/CT. MTVs of the primary tumour were calculated using an automated region-growing algorithm with SUV thresholds of 2.5 (MTV2.5) and ≥ 50% of SUVmax (MTV50%). Blinded for reconstruction method, a nuclear medicine physician assessed all lymph nodes showing ¹⁸F‑fluorodeoxyglucose uptake for their degree of suspicion.

RESULTS

The mean (95% CI) SUVmax of the primary tumour was 13.1 (10.6-15.5) versus 13.0 (10.4-15.6) for 3D and motion-compensated PET/CT, respectively. MTVs were also similar between the two techniques. Bland-Altman analysis showed mean differences between both measurements (95% limits of agreement) of 0.08 (-3.60-3.75), -0.26 (-2.34-1.82), 4.66 (-29.61-38.92) cm³ and -0.95 (-19.9-18.0) cm³ for tumour SUVmax, lymph node SUVmax, MTV2.5 and MTV50%, respectively. Lymph nodes were classified as highly suspicious (30/34 nodes), suspicious (20/22) and dubious (66/59) for metastases on 3D/motion-compensated PET/CT. No additional lymph node metastases were found on motion-compensated PET/CT. SUVmax of the most intense lymph nodes was similar for both scans: mean (95% CI) 6.6 (4.3-8.8) and 6.8 (4.5-9.1) for 3D and motion-compensated, respectively.

CONCLUSION

SUVmax of the primary oesophageal tumour and lymph nodes was comparable on 3D and motion-compensated PET/CT. The use of motion-compensated PET/CT did not improve lymph node detection.

Dose-escalated radiotherapy with PET/CT based treatment planning in combination with induction and concurrent chemotherapy in locally advanced (uT3/T4) squamous cell cancer of the esophagus: mature results of a phase I/II trial

BACKGROUND

This prospective phase I/II trial assessed feasibility and efficacy of dose-escalated definitive chemoradiation after induction chemotherapy in locally advanced esophageal cancer. Primary study endpoint was loco-regional progression-free survival at 1 year.

METHODS

Eligible patients received 2 cycles of induction chemotherapy with irinotecan, folinic acid and 5-fluorouracil weekly and cisplatin every 2 weeks (weeks 1-6, 8-13) followed by concurrent chemoradiation with cisplatin and irinotecan (weeks 14, 15, 17, 18, 20). Radiotherapy dose escalation was performed in three steps (60 Gy, 66 Gy, 72 Gy) using conventional fractionation, planning target volumes were delineated with the aid of 18F-FDG-PET/CT scans. During follow-up, endoscopic examinations were performed at regular intervals.

RESULTS

Between 09/2006 and 02/2010, 17 patients were enrolled (male/female:13/4, median age: 59 [range 48-66] years, stage uT3N0/T3N1/T4N1: 4/12/1). One patient progressed during induction chemotherapy and underwent surgery. Of 16 patients treated with definitive chemoradiotherapy, 9 (56%) achieved complete response after completion of chemoradiation. One-, 2-, 3- and 5-year overall survival rates (OS) were 77% [95%CI: 59-100], 53% [34-83], 41% [23-73], and 29% [14-61], respectively. Loco-regional progression-free survival at 1, 3, and 5 years was 59% [40-88], 35% [19-67], and 29% [14-61], corresponding cumulative incidences of loco-regional progressions were 18% [4-39%], 35% [14-58%], and 41% [17-64%]. No treatment related deaths occurred. Grade 3 toxicities during induction therapy were: neutropenia (41%), diarrhoea (41%), during combined treatment: neutropenia (62%) and thrombocytopenia (25%).

CONCLUSIONS

Dose-escalated radiotherapy and concurrent cisplatin/irinotecan after cisplatin/irinotecan/5FU induction chemotherapy was tolerable. The hypothesized phase II one-year loco-regional progression free survival rate of 74% was not achieved. Long-term survival compares well with other studies on definitive radiotherapy using irinotecan and cisplatin but is not better than recent trials using conventionally fractionated radiotherapy ad 50 Gy with concurrent paclitaxel or 5FU and platinum compound. Trial registration The present trial was registered as a phase I/II trial at the EudraCT database: Nr. 2005-006097-10 ( https://www.clinicaltrialsregister.eu/ctr-search/trial/2005-006097-10/DE ) and authorized to proceed on 2006-09-25.

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.

[F18] FDG-PET/CT for manual or semiautomated GTV delineation of the primary tumor for radiation therapy planning in patients with esophageal cancer: is it useful?

Background

Target volume definition of the primary tumor in esophageal cancer is usually based on computed tomography (CT) supported by endoscopy and/or endoscopic ultrasound and can be difficult given the low soft-tissue contrast of CT resulting in large interobserver variability. We evaluated the value of a dedicated planning [F18] FDG-Positron emission tomography/computer tomography (PET/CT) for harmonization of gross tumor volume (GTV) delineation and the feasibility of semiautomated structures for planning purposes in a large cohort.

Methods

Patients receiving a dedicated planning [F18] FDG-PET/CT (06/2011–03/2016) were included. GTV was delineated on CT and on PET/CT (GTV_CT and GTV_PET/CT, respectively) by three independent radiation oncologists. Interobserver variability was evaluated by comparison of mean GTV and mean tumor lengths, and via Sørensen–Dice coefficients (DSC) for spatial overlap. Semiautomated volumes were constructed based on PET/CT using fixed standardized uptake values (SUV) thresholds (SUV30, 35, and 40) or background- and metabolically corrected PERCIST-TLG and Schaefer algorithms, and compared to manually delineated volumes.

Results

45 cases were evaluated. Mean GTV_CT and GTV_PET/CT were 59.2/58.0 ml, 65.4/64.1 ml, and 60.4/59.2 ml for observers A–C. No significant difference between CT- and PET/CT-based delineation was found comparing the mean volumes or lengths. Mean Dice coefficients on CT and PET/CT were 0.79/0.77, 0.81/0.78, and 0.8/0.78 for observer pairs AB, AC, and BC, respectively, with no significant differences. Mean GTV volumes delineated semiautomatically with SUV30/SUV35/SUV40/Schaefer’s and PERCIST-TLG threshold were 69.1/23.9/18.8/18.6 and 70.9 ml. The best concordance of a semiautomatically delineated structure with the manually delineated GTV_CT/GTV_PET/CT was observed for PERCIST-TLG.

Conclusion

We were not able to show that the integration of PET/CT for GTV delineation of the primary tumor resulted in reduced interobserver variability. The PERCIST-TLG algorithm seemed most promising compared to other thresholds for further evaluation of semiautomated delineation of esophageal cancer.

Impact of 18F-FDG-PET/CT on the identification of regional lymph node metastases and delineation of the primary tumor in esophageal squamous cell carcinoma patients

Purpose

In patients undergoing chemoradiation for esophageal squamous cell carcinoma (ESCC), the extent of elective nodal irradiation (ENI) is still discussed controversially. This study aimed to analyze patterns of lymph node metastases and their correlation with the primary tumor using ¹⁸F‑fludeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) scans.

Methods

102 ESCC patients with pre-treatment FDG-PET/CT scans were evaluated retrospectively. After exclusion of patients with low FDG uptake and patients without FDG-PET-positive lymph node metastases (LNM), 76 patients were included in the final analysis. All LNM were assigned to 16 pre-defined anatomical regions and classified according to their position relative to the primary tumor (above, at the same height, or below the primary tumor). In addition, the longitudinal distance to the primary tumor was measured for all LNM above or below the primary tumor. The craniocaudal extent (i.e., length) of the primary tumor was measured using FDG-PET imaging (L_PET) and also based on all other available clinical and imaging data (endoscopy, computed tomography, biopsy results) except FDG-PET (L_CT/EUS).

Results

Significantly more LNM were identified with ¹⁸F‑FDG-PET/CT (177 LNM) compared to CT alone (131 LNM, p < 0.001). The most common sites of LNM were paraesophageal (63% of patients, 37% of LNM) and paratracheal (33% of patients, 20% of LNM), while less than 5% of patients had supraclavicular, subaortic, diaphragmatic, or hilar LNM. With regard to the primary tumor, 51% of LNM were at the same height, while 25% and 24% of lymph node metastases were above and below the primary tumor, respectively. For thirty-three LNM (19%), the distance to the primary tumor was larger than 4 cm. No significant difference was seen between L_CT/EUS (median 6 cm) and L_PET (median 6 cm, p = 0.846)

Conclusion

¹⁸F‑FDG-PET can help to identify subclinical lymph node metastases which are located outside of recommended radiation fields. PET-based involved-field irradiation might be the ideal compromise between small treatment volumes and decreasing the risk of undertreatment of subclinical metastatic lymph nodes and should be further evaluated.

Molecular Imaging in Photon Radiotherapy

Nowadays, more than ever before, the treatment of cancer patients requires an interdisciplinary approach more than ever. Radiation therapy (RT) has become an indispensable pillar of cancer treatment early on, offering a local, curative treatment option and symptom control in palliative cases.

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.

Prediction of response after chemoradiation for esophageal cancer using a combination of dosimetry and CT radiomics

PURPOSE

To investigate the treatment response prediction feasibility and accuracy of an integrated model combining computed tomography (CT) radiomic features and dosimetric parameters for patients with esophageal cancer (EC) who underwent concurrent chemoradiation (CRT) using machine learning.

METHODS

The radiomic features and dosimetric parameters of 94 EC patients were extracted and modeled using Support Vector Classification (SVM) and Extreme Gradient Boosting algorithm (XGBoost). The 94-sample dataset was randomly divided into a 70-sample training subset and a 24-sample independent test set while keeping the class proportions intact via stratification. A receiver operating characteristic (ROC) curve was used to assess the performance of models using radiomic features alone and using combined radiomic features and dosimetric parameters.

RESULTS

A total of 42 radiomic features and 18 dosimetric parameters plus the patients' characteristic parameters were extracted for these 94 cases (58 responders and 36 non-responders). XGBoost plus principal component analysis (PCA) achieved an accuracy and area under the curve of 0.708 and 0.541, respectively, for models with radiomic features combined with dosimetric parameters, and 0.689 and 0.479, respectively, for radiomic features alone. Image features of GlobalMean X.333.1, Coarseness, Skewness, and GlobalStd contributed most to the model. The dosimetric parameters of gross tumor volume (GTV) homogeneity index (HI), Cord Dmax, Prescription dose, Heart-Dmean, and Heart-V50 also had a strong contribution to the model.

CONCLUSIONS

The model with radiomic features combined with dosimetric parameters is promising and outperforms that with radiomic features alone in predicting the treatment response of patients with EC who underwent CRT.

KEY POINTS

• The model with radiomic features combined with dosimetric parameters is promising in predicting the treatment response of patients with EC who underwent CRT. • The model with radiomic features combined with dosimetric parameters (prediction accuracy of 0.708 and AUC of 0.689) outperforms that with radiomic features alone (best prediction accuracy of 0.625 and AUC of 0.412). • The image features of GlobalMean X.333.1, Coarseness, Skewness, and GlobalStd contributed most to the treatment response prediction model. The dosimetric parameters of GTV HI, Cord Dmax, Prescription dose, Heart-Dmean, and Heart-V50 also had a strong contribution to the model.

Texture analysis of computed tomography data using morphologic and metabolic delineation of esophageal cancer-relation to tumor type and neoadjuvant therapy response

The prognostic values of image-based tumor texture analysis based on computed tomography (CT) and of limiting the segmented tumor volume to metabolically active regions using fludeoxyglucose-positron emission tomography (FDG-PET) were studied in 25 patients with esophageal adenocarcinoma and 11 patients with squamous cell carcinoma. The aims of this study are to describe their CT-image-based texture characteristics before and after neoadjuvant therapy and to evaluate whether limiting the examined tumor volume to metabolically active regions detected with FDG-PET image data would further improve their value. Textural parameters (homogeneity, energy, entropy, contrast, and correlation) based on gray-level co-occurrence matrices (GLCM) were calculated for 3D volumes of segmented esophageal tumors before and after neoadjuvant chemotherapy or radiochemotherapy. Histopathological data after surgical resection and textural parameters before and after neoadjuvant treatment were compared using the Mann-Whitney U test. Significant differences in the textural parameters were observed between adenocarcinoma and squamous cell carcinoma for homogeneity, energy, inertia, and correlation. The use of contrast media during scanning resulted in significant differences in homogeneity, energy, entropy, and inertia for adenocarcinoma but not squamous cell carcinoma. There was also a significant difference in all textural parameters between pathological T status for ypT0-ypT2 and ypT3-ypT4 adenocarcinomas, but not in squamous cell carcinoma patients. No additional value was found from using PET image data to aid segmentation of CT images.

Present and future roles of FDG-PET/CT imaging in the management of gastrointestinal cancer: an update

Positron emission tomography/computed tomography (PET/CT) integrated with 2-[¹⁸F]fluoro-2-deoxy-D-glucose (FDG) is a useful tool for acquisition of both glucose metabolism and anatomic imaging data, as only a single device and one diagnostic session is required, thus opening a new field in clinical oncologic imaging. FDG-PET/CT has been successfully used for initial staging, restaging, assessment of early treatment response, evaluation of metastatic disease response, and prognostication of intestinal cancer as well as various malignant tumors. We reviewed the current status and role of FDG-PET/CT for management of patients with esophageal cancer, gastric cancer, and colorectal cancer, with focus on both its usefulness and limitations.

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.

A comparative study of quantitative assessment with fluorine-18-fluorodeoxyglucose positron-emission tomography and endoscopic ultrasound in oesophageal cancer

OBJECTIVES

This study aims to assess the correlation between PET/CT and endoscopic ultrasound (EUS) parameters in patients with oesophageal cancer.

PATIENTS AND METHODS

All patients who had complete PET/CT and EUS staging performed for oesophageal cancer at our centre between 2010 and 2016 were included. Images were retrieved and analysed for a range of parameters including tumour length, volume and position relative to the aortic arch.

RESULTS

Seventy patients were included in the main analysis. A strong correlation was found between EUS and PET/CT in the tumour length, the volume and the position of the tumour relative to the aortic arch. Regression modelling showed a reasonable predictive value for PET/CT in calculating EUS parameters, with r higher than 0.585 in some cases.

CONCLUSION

Given the strong correlation between EUS and PET parameters, fluorine-18 fluorodeoxyglucose (F-FDG) PET can provide accurate information on the length and the volume of tumour in patients who either cannot tolerate EUS or have impassable strictures.

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.

Biological imaging for individualized therapy in radiation oncology: part II medical and clinical aspects

Positron emission tomography and multiparametric MRI provide crucial information concerning tumor extent and normal tissue anatomy. Moreover, they are able to visualize biological characteristics of the tumor, which can be considered in the radiation treatment planning and monitoring. In this review we discuss the impact of biological imaging positron emission tomography and multiparametric MRI for radiation oncology, based on the data of the literature and on the experience of our own institution in this field.

18F-deoxyglucose positron emission tomography/computed tomography to predict local failure in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) patients are at risk for local failure (LF) following treatment. Predicting tumor regions at high risk for local failure before radiotherapy may increase treatment efficacy by permitting an escalated radiation dose specifically to those regions critical for tumor control. Forty-one patients with non-resectable locally advanced ESCC underwent ¹⁸F-deoxyglucose positron emission tomography/computed tomography (FDG PET/CT) imaging before concurrent chemoradiotherapy (CCRT). After CCRT, a second (failure) FDG PET/CT was performed in cases of relapse. Failure FDG PET/CT scans were fused to pre-treatment scans to identify tumor regions at high risk for LF. Within a median follow-up time of 26 months, 20 patients (48.8%) had LF. In 19 patients, the failure occurred within a pre-treatment high FDG uptake region; the failure occurred outside these regions in only one patient. Pre-treatment metabolic tumor volume (MTV) was independently associated with LF (P<0.001, HR 1.128, 95% CI: 1.061–1.198). LF was more likely in patients with MTVs ≥27 cm³. In initial PET/CT images, when 50% maximum standardized uptake value (SUV_max) was used as the threshold, delineated subvolumes overlapped LF regions. These results confirm that LF occurs most commonly within pre-treatment high FDG uptake regions.

Radiotherapy for esophageal carcinoma: dose, response and survival

Esophageal cancer (EC) is an extremely aggressive, lethal malignancy that is increasing in incidence worldwide. At present, definitive chemoradiotherapy is accepted as the standard treatment for locally advanced EC. The EC guidelines recommend a radiation dose of 50.4 Gy for definitive treatment, yet the outcomes for patients who have received standard-dose radiotherapy remain unsatisfactory. However, some studies indicate that a higher radiation dose could improve local tumor control, and may also confer survival benefits. Some studies, however, suggest that high-dose radiotherapy does not bring survival benefit. The available data show that most failures occurred in the gross target volume (especially in the primary tumor) after definitive chemoradiation. Based on those studies, we hypothesize that at least for some patients, more intense local therapy may lead to better local control and survival. The aim of this review is to evaluate the radiation dose, fractionation strategies, and predictive factors of response to therapy in functional imaging for definitive chemoradiotherapy in esophageal carcinoma, with an emphasis on seeking the predictive model of response to CRT and trying to individualize the radiation dose for EC patients.

Respiratory-gated (4D) contrast-enhanced FDG PET-CT for radiotherapy planning of lower oesophageal carcinoma: feasibility and impact on planning target volume

BACKGROUND

To assess the feasibility and potential impact on target delineation of respiratory-gated (4D) contrast-enhanced ¹⁸Fluorine fluorodeoxyglucose (FDG) positron emission tomography - computed tomography (PET-CT), in the treatment planning position, for a prospective cohort of patients with lower third oesophageal cancer.

METHODS

Fifteen patients were recruited into the study. Imaging included 4D PET-CT, 3D PET-CT, endoscopic ultrasound and planning 4D CT. Target volume delineation was performed on 4D CT, 4D CT with co-registered 3D PET and 4D PET-CT. Planning target volumes (PTV) generated with 4D CT (PTV_4DCT), 4D CT co-registered with 3D PET-CT (PTV_3DPET4DCT) and 4D PET-CT (PTV_4DPETCT) were compared with multiple positional metrics.

RESULTS

Mean PTV_4DCT, PTV_3DPET4DCT and PTV_4DPETCT were 582.4 ± 275.1 cm³, 472.5 ± 193.1 cm³ and 480.6 ± 236.9 cm³ respectively (no significant difference). Median DICE similarity coefficients comparing PTV_4DCT with PTV_3DPET4DCT, PTV_4DCT with PTV_4DPETCT and PTV_3DPET4DCT with PTV_4DPETCT were 0.85 (range 0.65-0.9), 0.85 (range 0.69-0.9) and 0.88 (range 0.79-0.9) respectively. The median sensitivity index for overlap comparing PTV_4DCT with PTV_3DPET4DCT, PTV_4DCT with PTV_4DPETCT and PTV_3DPET4DCT with PTV_4DPETCT were 0.78 (range 0.65-0.9), 0.79 (range 0.65-0.9) and 0.89 (range 0.68-0.94) respectively.

CONCLUSIONS

Planning 4D PET-CT is feasible with careful patient selection. PTV generated using 4D CT, 3D PET-CT and 4D PET-CT were of similar volume, however, overlap analysis demonstrated that approximately 20% of PTV_3DPETCT and PTV_4DPETCT are not included in PTV_4DCT, leading to under-coverage of target volume and a potential geometric miss. Additionally, differences between PTV_3DPET4DCT and PTV_4DPETCT suggest a potential benefit for 4D PET-CT.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier - NCT02285660 (Registered 21/10/2014).

PET/Computed Tomography Scanning and Precision Medicine: Esophageal Cancer

Esophageal cancer commonly has a poor prognosis, which requires an accurate diagnosis and early treatment to improve outcome. Other modalities for staging, such as endoscopic ultrasound imaging and computed tomography (CT) scans, have a role in diagnosis and staging. However, PET with fluorine-18 fluoro-2-deoxy-d-glucose/CT (FDG PET/CT) scanning allows for improved detection of distant metastatic disease and can help to prevent unnecessary interventions that would increase morbidity. FDG PET/CT scanning is valuable in the neoadjuvant chemotherapy assessment and predicting survival outcomes subsequent to surgery. FDG PET/CT scanning detects recurrent disease and metastases in follow-up.

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.

Application of PET/CT in gastrointestinal cancers

Fluorine-18 fluoro-2-deoxy-D-glucose positron emission tomography (¹⁸F-FDG PET) is an imaging tool which reflects tumor metabolism. The integration of PET with computed tomography (CT) can provide precise anatomical information along with metabolic data. Here, we review the application and potential role of ¹⁸F-FDG PET/CT imaging in staging, evaluation of chemoradiation therapy, and detection of recurrence in gastrointestinal cancers.

Radiation field size and dose determine oncologic outcome in esophageal cancer

Background

Locoregional recurrence is a major problem in esophageal cancer patients treated with definitive concomitant chemoradiotherapy. Approximately half of the patients fail locoregionally. We analyzed the impact of enlarged radiation field size and higher radiation dose incorporated to chemoradiotherapy on oncologic outcome.

Methods

Seventy-four consecutive patients with histologically proven nonmetastatic squamous or adenocarcinoma of the esophagus were included in this retrospective analysis. All patients were locally advanced cT3–T4 and/or cN0-1. Treatment consisted of either definitive concomitant chemoradiotherapy (Def-CRT) (n = 49, 66 %) or preoperative concomitant chemoradiotherapy (Pre-CRT) followed by surgical resection (n = 25, 34 %). Patients were treated with longer radiation fields. Clinical target volume (CTV) was obtained by giving 8–10 cm margins to the craniocaudal borders of gross tumor volume (GTV) instead of 4–5 cm globally accepted margins, and some patients in Def-CRT group received radiation doses higher than 50 Gy.

Results

Isolated locoregional recurrences were observed in 9 out of 49 patients (18 %) in the Def-CRT group and in 1 out of 25 patients (3.8 %) in the Pre-CRT group (p = 0.15). The 5-year survival rate was 59 % in the Def-CRT group and 50 % in the Pre-CRT group (p = 0.72). Radiation dose was important in the Def-CRT group. Patients treated with >50 Gy (11 out of 49 patients) had better survival with respect to patients treated with 50 Gy (38 out of 49 patients). Five-year survivals were 91 and 50 %, respectively (p = 0.013).

Conclusions

Radiation treatment planning by enlarged radiation fields in esophageal cancer decreases locoregional recurrences considerably with respect to the results reported in the literature by standard radiation fields (18 vs >50 %). Radiation dose is as important as radiation field size; patients in the Def-CRT group treated with ≥50 Gy had better survival in comparison to patients treated with 50 Gy.

Impact of PET/CT on radiation treatment in patients with esophageal cancer: A systematic review

PURPOSE

With the advances in radiotracers, positron emission tomography/computed tomography (PET/CT) is recognized as a useful adjunct to anatomic imaging with CT, MRI and endoscopic ultrasonography (EUS). The objective of this review was to comprehensively analyze the roles of PET/CT for the radiotherapy of esophageal cancer.

METHODS

In this review, we focused on issues concerning the application of PET/CT in TNM staging, target volume delineation and response to therapy, both for the primary tumor and regional lymph nodes. Furthermore, the following questions were addressed: how does PET/CT guide appropriate treatment protocols, how does it allow accurate tumor delineation and how does it guide prognosis and future treatment decisions.

RESULTS AND CONCLUSION

For the staging of esophageal cancer, PET/CT played a crucial role in exploring distant malignant lymph nodes and metastasis with high sensitivity, specificity and accuracy. PET/CT using different radiotracer provided a serial of thresholding methods based on standardized uptake value (SUV) to assist in auto-contouring the gross tumor volume (GTV). The change in SUV may offer a potential paradigm of personalized treatment to definitive chemoradiotherapy (CRT). In total, PET/CT has sought to further optimize radiotherapy treatment planning for patients with esophageal cancer.

Superiority of Deformable Image Co-registration in the Integration of Diagnostic Positron Emission Tomography-Computed Tomography to the Radiotherapy Treatment Planning Pathway for Oesophageal Carcinoma

AIMS

To investigate the use of image co-registration in incorporating diagnostic positron emission tomography-computed tomography (PET-CT) directly into the radiotherapy treatment planning pathway, and to describe the pattern of local recurrence relative to the PET-avid volume.

MATERIALS AND METHODS

Fourteen patients were retrospectively identified, six of whom had local recurrence. The accuracy of deformable image registration (DIR) and rigid registration of the diagnostic PET-CT and recurrence CT, to the planning CT, were quantitatively assessed by comparing co-registration of oesophagus, trachea and aorta contours. DIR was used to examine the correlation between PET-avid volumes, dosimetry and site of recurrence.

RESULTS

Positional metrics including the dice similarity coefficient (DSC) and conformity index (CI), showed DIR to be superior to rigid registration in the co-registration of diagnostic and recurrence imaging to the planning CT. For diagnostic PET-CT, DIR was superior to rigid registration in the transfer of oesophagus (DSC=0.75 versus 0.65, P<0.009 and CI=0.59 versus 0.48, P<0.003), trachea (DSC=0.88 versus 0.65, P<0.004 and CI=0.78 versus 0.51, P<0.0001) and aorta structures (DSC=0.93 versus 0.86, P<0.006 and CI=0.86 versus 0.76, P<0.006). For recurrence imaging, DIR was superior to rigid registration in the transfer of trachea (DSC=0.91 versus 0.66, P<0.03 and CI=0.83 versus 0.51, P<0.02) and oesophagus structures (DSC=0.74 versus 0.51, P<0.004 and CI=0.61 versus 0.37, P<0.006) with a non-significant trend for the aorta (DSC=0.91 versus 0.75, P<0.08 and CI=0.83 versus 0.63, P<0.06) structure. A mean inclusivity index of 0.93 (range 0.79-1) showed that the relapse volume was within the planning target volume (PTVPET-CT); all relapses occurred within the high dose region.

CONCLUSION

DIR is superior to rigid registration in the co-registration of PET-CT and recurrence CT to the planning CT, and can be considered in the direct integration of PET-CT to the treatment planning process. Local recurrences occur within the PTVPET-CT, suggesting that this is a suitable target for dose-escalation strategies.

Distribution of lymph node metastases on FDG-PET/CT in inoperable or unresectable oesophageal cancer patients and the impact on target volume definition in radiation therapy

INTRODUCTION

Definitive chemoradiotherapy (dCRT) is standard care for localised inoperable/unresectable oesophageal tumours. Many surgical series have reported on distribution of lymph node metastases (LNM) in resected patients. However, no data is available on the distribution of at-risk LN regions in this more unfavourable patient group. This study aimed to determine the spread of LNM using FDG-PET/CT, to compare it with the distribution in surgical series and to define its impact on the definition of elective LN irradiation (ENI).

METHODS

FDG-PET/CT images of patients with oesophageal cancer treated with dCRT (from 2003 to 2013) were reviewed to identify the anatomic distribution of FDG-avid LNs. Tumours were divided according to proximal, mid-thoracic or distal localisation.

RESULTS

About 105 consecutive patients entered analysis. The highest numbers of FDG-avid LNs in proximal tumours were at LN station 101R (45%) and 106recL (35%). For mid-thoracic tumours at 104R (30%) and 105 (30%). For tumours located in the distal oesophagus, the most common sites were along the lesser curvature of the stomach (21%) and the left gastric artery (21%). Except for the supraclavicular and pretracheal nodes, there were no positive locoregional LNM found outside the standard surgical resection area.

CONCLUSION

Our results show a good correlation between the distribution of nodal volumes at risk in surgical series and on FDG-PET/CT. The results can be used to determine target definition in dCRT for oesophageal cancer. For mid-thoracic tumours, the current target delineation guidelines may be extended based on the risk of node involvement, but more clinical studies are needed to determine if the potential harm of expanding the CTV outweighs the potential benefit.

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.

Melanin nanoparticles derived from a homology of medicine and food for sentinel lymph node mapping and photothermal in vivo cancer therapy

The use of non-toxic or low toxicity materials exhibiting dual functionality for use in sentinel lymph node (SLN) mapping and cancer therapy has attracted considerable attention during the past two decades. Herein, we report that the natural black sesame melanin (BSM) extracted from black sesame seeds (Sesamum indicum L.) shows exciting potential for SLN mapping and cancer photothermal therapy. Aqueous solutions of BSM under neutral and alkaline conditions can assemble into sheet-like nanoparticles ranging from 20 to 200 nm in size. The BSM nanoparticles were encapsulated by liposomes to improve their water solubility and the encapsulated and bare BSM nanoparticles were both non-toxic to cells. Furthermore, the liposome-encapsulated BSM nanoparticles (liposome-BSM) did not exhibit any long-term toxicity in mice. The liposome-BSM nanoparticles were subsequently used to passively target healthy and tumor-bearing mice SLNs, which were identified by the black color of the nanoparticles. BSM also strongly absorbed light in the near-infrared (NIR) range, which was rapidly converted to heat energy. Human esophagus carcinoma cells (Eca-109) were killed efficiently by liposome-BSM nanocomposites upon NIR laser irradiation. Furthermore, mouse tumor tissues grown from Eca-109 cells were seriously damaged by the photothermal effects of the liposome-BSM nanocomposites, with significant tumor growth suppression compared with controls. Given that BSM is a safe and nutritious biomaterial that can be easily obtained from black sesame seed, the results presented herein represent an important development in the use of natural biomaterials for clinical SLN mapping and cancer therapy.

A Multimodal System with Synergistic Effects of Magneto-Mechanical, Photothermal, Photodynamic and Chemo Therapies of Cancer in Graphene-Quantum Dot-Coated Hollow Magnetic Nanospheres

In this study, a multimodal therapeutic system was shown to be much more lethal in cancer cell killing compared to a single means of nano therapy, be it photothermal or photodynamic. Hollow magnetic nanospheres (HMNSs) were designed and synthesized for the synergistic effects of both magneto-mechanical and photothermal cancer therapy. By these combined stimuli, the cancer cells were structurally and physically destroyed with the morphological characteristics distinctively different from those by other therapeutics. HMNSs were also coated with the silica shells and conjugated with carboxylated graphene quantum dots (GQDs) as a core-shell composite: HMNS/SiO2/GQDs. The composite was further loaded with an anticancer drug doxorubicin (DOX) and stabilized with liposomes. The multimodal system was able to kill cancer cells with four different therapeutic mechanisms in a synergetic and multilateral fashion, namely, the magnetic field-mediated mechanical stimulation, photothermal damage, photodynamic toxicity, and chemotherapy. The unique nanocomposites with combined mechanical, chemo, and physical effects will provide an alternative strategy for highly improved cancer therapy efficiency.

Patterns of nodal metastases on 18F-FDG PET/CT in patients with esophageal squamous cell carcinoma are useful to guide treatment planning of radiotherapy

BACKGROUND AND PURPOSES

The aim of the study was to examine the patterns of lymph node metastases from esophageal squamous cell carcinoma (ESCC) and compare the laterality of lymphatic metastasis in cervical, supraclavicular, and paratracheal areas using F-FDG PET/CT.

PATIENTS AND METHODS

The data of 75 patients who underwent F-FDG PET/CT for staging of ESCC between January 2011 and March 2012 were reviewed. Fourteen groups of lymph nodes from the neck to abdomen were defined. Lateralization of the upper thoracic lymph nodes was defined in reference to the midline of the trachea. Frequencies of positive lymph nodes were used to determine the pattern of lymphatic spread and compare the lateralization of metastases in the cervical and upper thoracic regions.

RESULTS

The right paratracheal region was the most frequent site of metastasis among all patients. Left paratracheal and paragastric nodes were more frequent in upper and lower third ESCC, respectively. Upward and downward lymphatic spread was equal in mid third ESCC. In all patients, there was a trend toward more frequent lymph node metastasis on the right side than the left side for the supraclavicular and paratracheal regions. Further stratified analysis with tumor location found that right paratracheal node metastasis was significantly associated with mid third ESCC (P = 0.03). Remote nodal metastasis was found in 10.5% of patients with upper third ESCC and 13% of patients with lower third ESCC, respectively. Remote nodal metastasis was associated with higher SUV of the primary tumor (P = 0.02) and worse survival (P = 0.03). Receiver operating characteristic analysis showed a cutoff SUV of 14.8 for predicting remote lymph node metastases.

CONCLUSIONS

PET/CT provides important information before radiotherapy planning. Mid and lower third ESCC tends to metastasize to the right paratracheal/supraclavicular lymph nodes. Remote nodal metastases on PET/CT correlated with higher primary tumor SUV and worse survival.

FDG-PET/CT during concomitant chemo radiotherapy for esophageal cancer: Reducing target volumes to deliver higher radiotherapy doses

BACKGROUND

A planning study investigated whether reduced target volumes defined on FDG-PET/CT during radiotherapy allow total dose escalation without compromising normal tissue tolerance in patients with esophageal cancer.

MATERIAL AND METHODS

Ten patients with esophageal squamous cell carcinoma (SCC), candidate to curative-intent concomitant chemo-radiotherapy (CRT), had FDG-PET/CT performed in treatment position, before and during (Day 21) radiotherapy (RT). Four planning scenarios were investigated: 1) 50 Gy total dose with target volumes defined on pre-RT FDG-PET/CT; 2) 50 Gy with boost target volume defined on FDG-PET/CT during RT; 3) 66 Gy with target volumes from pre-RT FDG-PET/CT; and 4) 66 Gy with boost target volume from during-RT FDG-PET/CT.

RESULTS

The median metabolic target volume decreased from 12.9 cm3 (minimum 3.7-maximum 44.8) to 5.0 cm3 (1.7-13.5) (p=0.01) between pre- and during-RCT FDG-PET/CT. The median PTV66 was smaller on during-RT than on baseline FDG-PET/CT [108 cm3 (62.5-194) vs. 156 cm3 (68.8-251), p=0.02]. When total dose was set to 50 Gy, planning on during-RT FDG-PET/CT was associated with a marginal reduction in normal tissues irradiation. When total dose was increased to 66 Gy, planning on during-RT PET yielded significantly lower doses to the spinal cord [Dmax=44.1Gy (40.8-44.9) vs. 44.7Gy (41.5-45.0), p=0.007] and reduced lung exposure [V20Gy=23.2% (17.3-27) vs. 26.8% (19.7-30.2), p=0.006].

CONCLUSION

This planning study suggests that adaptive RT based on target volume reduction assessed on FDG-PET/CT during treatment could facilitate dose escalation up to 66 Gy in patients with esophageal SCC.

The role of PET-CT in radiotherapy planning of solid tumours

Background

PET-CT is becoming more and more important in various aspects of oncology. Until recently it was used mainly as part of diagnostic procedures and for evaluation of treatment results. With development of personalized radiotherapy, volumetric and radiobiological characteristics of individual tumour have become integrated in the multistep radiotherapy (RT) planning process. Standard anatomical imaging used to select and delineate RT target volumes can be enriched by the information on tumour biology gained by PET-CT. In this review we explore the current and possible future role of PET-CT in radiotherapy treatment planning. After general explanation, we assess its role in radiotherapy of those solid tumours for which PET-CT is being used most.

Conclusions

In the nearby future PET-CT will be an integral part of the most radiotherapy treatment planning procedures in an every-day clinical practice. Apart from a clear role in radiation planning of lung cancer, with forthcoming clinical trials, we will get more evidence of the optimal use of PET-CT in radiotherapy planning of other solid tumours.

Safety of dose escalation by simultaneous integrated boosting radiation dose within the primary tumor guided by (18)FDG-PET/CT for esophageal cancer

PURPOSE

To observe the safety of selective dose boost to the pre-treatment high (18)F-deoxyglucose (FDG) uptake areas of the esophageal GTV.

METHODS

Patients with esophageal squamous cell carcinoma were treated with escalating radiation dose of 4 levels, with a simultaneous integrated boost (SIB) to the pre-treatment 50% SUVmax area of the primary tumor. Patients received 4 monthly cycles of cisplatin and fluorouracil. Dose-limiting toxicity (DLT) was defined as any Grade 3 or higher acute toxicities causing continuous interruption of radiation for over 1 week.

RESULTS

From April 2012 to February 2014, dose has been escalated up to LEVEL 4 (70Gy). All of the 25 patients finished the prescribed dose without DLT, and 10 of them developed Grade 3 acute esophagitis. One patient of LEVEL 2 died of esophageal hemorrhage within 1 month after completion of radiotherapy, which was not definitely correlated with treatment yet. Late toxicities remained under observation. With median follow up of 8.9months, one-year overall survival and local control was 69.2% and 77.4%, respectively.

CONCLUSIONS

Dose escalation in esophageal cancer based on (18)FDG-PET/CT has been safely achieved up to 70Gy using the SIB technique. Acute toxicities were well tolerated, whereas late toxicities and long-term outcomes deserved further observation.

Defining the target in cancer of the oesophagus: direct radiotherapy planning with fluorodeoxyglucose positron emission tomography-computed tomography

AIMS

Target definition in radiotherapy treatment planning (RTP) of oesophageal cancer is challenging and guided by a combination of diagnostic modalities. This planning study aimed to evaluate the contribution of single positron emission tomography-computed tomography (PET-CT) in the treatment position to RTP.

MATERIALS AND METHODS

Nineteen patients referred for radiotherapy from April to December 2008 were retrospectively identified. Two sets of target volumes were delineated using the planning CT and the (18)F-fluoro-deoxy-D-glucose ((18)F-FDG) PET-CT data sets, respectively. Target volumes were compared in length, volume and geographic conformality. Radiotherapy plans were generated and compared for both data sets.

RESULTS

PET-CT planning target volume (PET-CT(PTV)) was larger than the CT target (CT(PTV)) in 12 cases and smaller in seven. The median PTV conformality index was 0.82 (range 0.44-0.98). Radiotherapy plans conforming to normal tissue dose constraints were achieved for both sets of PTV in 16 patients (three patients could not be treated to the prescription dose with either technique due to very large target volumes and significant risk of normal tissue toxicity). Previously undetected locoregional nodal involvement seen on PET-CT in three cases was localised and included in the PTV. In nine cases, the CTPTV plan delivered less than 95% dose to 95% of the PET-CT(PTV), raising concern about potential for geographical miss.

CONCLUSION

A single scan with diagnostic PET-CT in the treatment position for RTP allows greater confidence in anatomical localisation and interpretation of biological information. The use of PET-CT may result in larger PTV volumes in selected cases, but did not exclude patients from radical treatment within accepted normal tissue tolerance.

Clinical validation of FDG-PET/CT in the radiation treatment planning for patients with oesophageal cancer

BACKGROUND

The aim of this prospective study was to determine the proportion of locoregional recurrences (LRRs) that could have been prevented if radiotherapy treatment planning for oesophageal cancer was based on PET/CT instead of CT.

MATERIALS AND METHODS

Ninety oesophageal cancer patients, eligible for high dose (neo-adjuvant) (chemo)radiotherapy, were included. All patients underwent a planning FDG-PET/CT-scan. Radiotherapy target volumes (TVs) were delineated on CT and patients were treated according to the CT-based treatment plans. The PET images remained blinded. After treatment, TVs were adjusted based on PET/CT, when appropriate. Follow up included CT-thorax/abdomen every 6months. If LRR was suspected, a PET/CT was conducted and the site of recurrence was compared to the original TVs. If the LRR was located outside the CT-based clinical TV (CTV) and inside the PET/CT-based CTV, we considered this LRR possibly preventable.

RESULTS

Based on PET/CT, the gross tumour volume (GTV) was larger in 23% and smaller in 27% of the cases. In 32 patients (36%), >5% of the PET/CT-based GTV would be missed if the treatment planning was based on CT. The median follow up was 29months. LRRs were seen in 10 patients (11%). There were 3 in-field recurrences, 4 regional recurrences outside both CT-based and PET/CT-based CTV and 3 recurrences at the anastomosis without changes in TV by PET/CT; none of these recurrences were considered preventable by PET/CT.

CONCLUSION

No LRR was found after CT-based radiotherapy that could have been prevented by PET/CT. The value of PET/CT for radiotherapy seems limited.

Radiographic and endosonographic staging in esophageal cancer

Radiographic imaging using computed tomographic (CT) scan and positron emission tomography/CT are primarily helpful in identifying distant metastases. In general, if patients have evidence of lymph node involvement that is proved pathologically by endoscopic ultrasound/fine needle aspiration, this information is considered definitive, and the patient can be referred for the appropriate stage-specific therapy. Laparoscopy combined with laparoscopic ultrasound and peritoneal lavage has been shown to have sensitivity of 67% and specificity of 92% for lymph node disease. Thoracoscopy may help identify involved lymph node in the mediastinum before resection and help determine the field of radiation.

Esophagectomy for failed endoscopic therapy in patients with high-grade dysplasia or intramucosal carcinoma

Endoscopic therapy (ablation +/- endoscopic resection) for high-grade dysplasia and/or intramucosal carcinoma (IMC) of the esophagus has demonstrated promising results. However, there is a concern that a curable, local disease may progress to systemic disease with repeated endotherapy. We performed a retrospective review of patients who underwent esophagectomy after endotherapy at three tertiary care esophageal centers from 2006 to 2012. Our objective was to document the clinical and pathologic outcomes of patients who undergo esophagectomy after failed endotherapy. Fifteen patients underwent esophagectomy after a mean of 13 months and 4.1 sessions of endotherapy for progression of disease (53%), failure to clear disease (33%), or recurrence (13%). Initially, all had Barrett's, 73% had ≥3-cm segments, 93% had a nodule or ulcer, and 91% had multifocal disease upon presentation. High-grade dysplasia was present at index endoscopy in 80% and IMC in 33%, and some patients had both. Final pathology at esophagectomy was T0 (13%), T1a (60%), T1b (20%), and T2 (7%). Positive lymph nodes were found in 20%: one patient was T2N1 and two were T1bN1. Patients with T1b, T2, or N1 disease had more IMC on index endoscopy (75% vs. 18%) and more endotherapy sessions (median 6.5 vs. 3). There have been no recurrences a mean of 20 months after esophagectomy. Clinical outcomes were comparable to other series, but submucosal invasion (27%) and node-positive disease (20%) were encountered in some patients who initially presented with a locally curable disease and eventually required esophagectomy after failed endotherapy. An initial pathology of IMC or failure to clear disease after three treatments should raise concern for loco-regional progression and prompt earlier consideration of esophagectomy.