Using 18F-fluorodeoxyglucose positron emission tomography to estimate the length of gross tumor in patients with squamous cell carcinoma of the esophagus

PET/CT and MR Improve Interobserver Agreement in Primary Tumor Determination for Radiotherapy in Esophageal Squamous Cell Cancer

Background/Objectives: The aim of the study was to evaluate interobserver variability in the determination of the primary tumor for radiotherapy treatment planning in esophageal squamous cell carcinoma (ESCC). Methods: Sixteen patients with locally advanced ESCC were included in the analysis. In all patients positron emission tomography with computed tomography (PETC/CT) and magnetic resonance (MR) scans for radiotherapy planning were performed. Five experienced radiation oncologists delineated the primary tumor based on CT alone, MR alone, PET/CT, CT with fused MR and PET/CT with fused MR. Mean tumor volumes were calculated for each patient and imaging modality. The generalized conformity index (CIgen) was calculated to assess agreement in tumor determination. Results: The mean tumor volumes and CIgen for CT alone, MR alone, PET/CT, CT with fused MR and PET/CT with fused MR were 33.1 cm3, 30.2 cm3, 38.1 cm3, 31.9 cm3, 36.2 cm3 and 0.59, 0.64, 0.66, 0.63, 0.71, respectively. CIgen was significantly higher using PET/CT with fused MR compared to CT (p < 0.001) and PET/CT (p = 0.002) and using PET/CT compared to CT (alone) (p = 0.003). Conclusions: Our study showed higher agreement in primary tumor determination in ESCC using PET/CT compared to CT alone. Higher agreement was also found using PET/CT with fused MR compared to CT alone and PET/CT.

Inter-observer variation in gross tumour volume delineation of oesophageal cancer on MR, CT and PET/CT

BACKGROUND

The aim of our study was to assess the inter-observer variability in delineation of the gross tumour volume (GTV) of oesophageal cancer on magnetic resonance (MR) in comparison to computed tomography (CT) and positron emission tomography and CT (PET/CT).

PATIENTS AND METHODS

Twenty-three consecutive patients with oesophageal cancer treated with chemo-radiotherapy were enrolled. All patients had PET/CT and MR imaging in treatment position. Five observers independently delineated the GTV on CT alone, MR alone, CT with co-registered MR, PET/CT alone and MR with co-registered PET/CT. Volumes of GTV were measured per patient and imaging modality. Inter-observer agreement, expressed in generalized conformity index (CIgen), volumetric conformity index (VCI), planar conformity index (PCI) and inter-delineation distance (IDD) were calculated per patient and imaging modality. Linear mixed models were used for statistical analysis.

RESULTS

GTV volume was significantly lower on MR (33.03 cm3) compared to CT (37.1 cm3; p = 0.002) and on PET/CT MR (35.2 cm3; p = 0.018) compared to PET/CT (39.1 cm3). The CIgen was lowest on CT (0.56) and highest on PET/CT MR (0.67). The difference in CIgen between MR (0.61) and CT was borderline significant (p = 0.048). The VCI was significantly higher on MR (0.71; p = 0.007) and on CT MR (0.71; p = 0.004) compared to CT (0.67). The PCI was significantly higher on CT MR (0.67; p = 0.031) compared to CT (0.64). The largest differences were observed in the cranio-caudal direction.

CONCLUSIONS

The highest inter-observer agreement was found for PET/CT MR and the lowest for CT. MR could reduce the difference in delineation between observers and provide additional information about the local extent of the tumour.

Enhancing Prediction for Tumor Pathologic Response to Neoadjuvant Immunochemotherapy in Locally Advanced Esophageal Cancer by Dynamic Parameters from Clinical Assessments

To develop accurate and accessible prediction methods for assessing pathologic response following NICT prior to surgery, we conducted a retrospective study including 137 patients with esophageal squamous cell carcinoma (ESCC) who underwent surgery after two cycles of NICT between January 2019 and March 2022 at our center. We collected clinical parameters to evaluate the dynamic changes in the primary tumor. Univariate and multivariate analyses were performed to determine the correlations between these parameters and the pathologic response of the primary tumor. Subsequently, we constructed prediction models for pCR and MPR using multivariate logistic regression. The MPR prediction Model 2 was internally validated using bootstrapping and externally validated using an independent cohort from our center. The univariate logistic analysis revealed significant differences in clinical parameters reflecting tumor regression among patients with varying pathologic responses. The clinical models based on these assessments demonstrated excellent predictive performance, with the training cohort achieving a C-index of 0.879 for pCR and 0.912 for MPR, while the testing cohort also achieved a C-index of 0.912 for MPR. Notably, the MPR prediction Model 2, with a threshold cut-off of 0.74, exhibited 92.7% specificity and greater than 70% sensitivity, indicating a low rate of underestimating residual tumors. In conclusion, our study demonstrated the high accuracy of clinical assessment-based models in pathologic response prediction, aiding in decision-making regarding organ preservation and radiotherapy adjustments after induction immunochemotherapy.

The Role of MRI and PET/CT in Radiotherapy Target Volume Determination in Gastrointestinal Cancers-Review of the Literature

Positron emission tomography with computed tomography (PET/CT) and magnetic resonance imaging (MRI) could improve accuracy in target volume determination for gastrointestinal cancers. A systematic search of the PubMed database was performed, focusing on studies published within the last 20 years. Articles were considered eligible for the review if they included patients with anal canal, esophageal, rectal or pancreatic cancer, as well as PET/CT or MRI for radiotherapy treatment planning, and if they reported interobserver variability or changes in treatment planning volume due to different imaging modalities or correlation between the imaging modality and histopathologic specimen. The search of the literature retrieved 1396 articles. We retrieved six articles from an additional search of the reference lists of related articles. Forty-one studies were included in the final review. PET/CT seems indispensable for target volume determination of pathological lymph nodes in esophageal and anal canal cancer. MRI seems appropriate for the delineation of primary tumors in the pelvis as rectal and anal canal cancer. Delineation of the target volumes for radiotherapy of pancreatic cancer remains challenging, and additional studies are needed.

Imaging Recommendations for Diagnosis, Staging, and Management of Esophageal Cancer

Early staging and treatment initiation affect prognosis of patients with esophageal and esophagogastric junction cancer; hence, it is imperative to have knowledge of proper choice of imaging modality for staging of these patients, to effectively convey relevant imaging findings to the treating physician/surgeon. It is also essential to be aware of pertinent imaging findings that need to be conveyed to the treating physician/surgeon at staging, and after treatment, including post-therapy complications (if any), so as to provide timely management to such patients. In this article, we have provided imaging guidelines for diagnosis, staging, post-therapy response evaluation, follow-up, and assessment of post-therapy complications of esophageal and esophagogastric junction cancer in a systematic manner. Besides, risk factors and clinical workup have also been elucidated. We have also attached comprehensive staging and post-therapy contrast-enhanced computed tomography and fluorodeoxyglucose-positron emission tomography/computed tomography-based synoptic reporting formats “ECI-RADS” and “pECI-RADS,” respectively, for esophageal and esophagogastric junction cancer in the supplement, for effective communication of imaging findings between a radiologist and the treating physician/surgeon.

Prognostic Value of [18F]-FDG PET/CT Radiomics Combined with Sarcopenia Status among Patients with Advanced Gastroesophageal Cancer

We investigated, whether 18[18F]-FDG PET/CT-derived radiomics combined with sarcopenia measurements improves survival prognostication among patients with advanced, metastatic gastroesophageal cancer. In our study, 128 consecutive patients with advanced, metastatic esophageal and gastroesophageal cancer (n = 128; 26 females; 102 males; mean age 63.5 ± 11.7 years; age range: 29−91 years) undergoing 18[18F]-FDG PET/CT for staging between November 2008 and December 2019 were included. Segmentation of the primary tumor and radiomics analysis derived from PET and CT images was performed semi-automatically with a commonly used open-source software platform (LIFEX, Version 6.30, lifexsoft.org). Patients’ nutritional status was determined by measuring the skeletal muscle index (SMI) at the level of L3 on the CT component. Univariable and multivariable analyses were performed to establish a survival prediction model including radiomics, clinical data, and SMI score. Univariable Cox proportional hazards model revealed ECOG (<0.001) and bone metastasis (p = 0.028) to be significant clinical parameters for overall survival (OS) and progression free survival (PFS). Age (p = 0.017) was an additional prognostic factor for OS. Multivariable analysis showed improved prognostication for overall and progression free survival when adding sarcopenic status, PET and CT radiomics to the model with clinical parameters only. PET and CT radiomics derived from hybrid 18[18F]-FDG PET/CT combined with sarcopenia measurements and clinical parameters may improve survival prediction among patients with advanced, metastatic gastroesophageal cancer.

Measuring distance from the incisors to the esophageal cancer by FDG PET/CT: endoscopy as the reference

BACKGROUND

Using endoscopy as the reference, this study evaluated the accuracy of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) in measuring distance from the incisors to the PET detectable esophageal cancer. If there is high concordance between endoscopic and PET measurements, our results may provide a basis to use FDG PET/CT in cooperation with endoscopic measurement to localize those PET/CT and CT undetectable esophageal tumors for radiotherapy planning.

MATERIALS

Esophageal cancer patients with pretreatment endoscopy and FDG PET/CT detectable esophageal tumors were recruited retrospectively. The distances from the incisors to the proximal esophageal tumor margins were determined by endoscopy and by the sagittal images of FDG PET/CT. The endoscopic measurement was used as the comparative reference. A nuclear medicine doctor and a radiation oncologist each performed the FDG PET/CT measurement twice for every patient. We analyzed the differences in these measurements, and assessed agreement and reproducibility of the results by the intraclass correlation coefficient (ICC).

RESULTS

Thirty-four patients, with 35 esophageal tumors, were included. By endoscopy and FDG PET/CT, the mean distances from the incisors to the proximal esophageal tumor margin were 27.3 ± 6.4 cm (range 17.1-40.0 cm) and 26.8 ± 6.3 cm (range 15.7-41.3 cm), respectively. The mean absolute differences between the endoscopic and four FDG PET/CT measurements ranged from 1.129 to 1.289 cm (SD: 0.98-1.19). The measurement agreement between FDG PET/CT and endoscopy by ICC was between 0.962 and 0.971. The intra- and interobserver reproducibilities of the two readers were excellent (intraobserver ICC: 0.985, 0.996; interobserver ICC: 0.976-0.984).

CONCLUSIONS

FDG PET/CT was in high agreement with endoscopy in measuring the distance from the incisors to the proximal esophageal tumor margin. For FDG PET/CT and CT undetectable esophageal cancer, incorporation of the endoscopic measurement with PET/CT might be a way for making radiotherapy plan.

Dosimetric impact of positron emission tomography-based gross tumour volume (GTV) delineation over conventional CT-based GTV delineation for carcinoma oesophagus

Aim:

The aim of the study was to find the dosimetric impact of positron emission tomography (PET)-based gross tumour volume (GTV) delineation over computed tomography (CT)-based GTV delineation for carcinoma oesophagus.

Methods:

Fifteen patients with carcinoma oesophagus were retrospectively selected. Two sets of GTVs in CT plain images were generated, one with the help of intravenous and oral contrast (GTV CT) and the other with only using PET uptake with the standardised uptake value (simple way of determining the activity in PET) (SUV) > 2.5 (GTV PET). Corresponding PTVs were generated. For all patients, rapid arc plans were generated. Changes in target volumes and critical structure doses were evaluated. The Wilcoxon signed-rank test was used for statistical analysis, and p value < 0.05 was assumed as statistically significant.

Results:

Mean reduction in GTV was 5.76 ± 19.35 cc. Mean reduction in PTV 45 Gy was 42.40 ± 76.39 cc. Mean reduction in heart mean dose was 1.53 ± 2.16 Gy. Mean reductions in left lung V20% and V10% were 2.43 ± 4.28 and 3.25 ± 5.09 Gy, respectively. Mean reductions in right lung V20% and V10% were 3.11 ± 4.91 and 2.80 ± 4.51 Gy, respectively. Mean reduction in total lung mean dose was 1.00 ± 1.19 Gy.

Finding:

PET-based GTV contouring reduces the treatment volume and critical structure doses significantly over CT-based GTV contouring for carcinoma oesophagus.

18F-FDG PET/CT Parameters for Predicting Prognosis in Esophageal Cancer Patients Treated With Concurrent Chemoradiotherapy

Background and Aims:

This study evaluated the prognostic value of ¹⁸F-fluorodeoxyglucose positron emission tomography with integrated computed tomography (¹⁸F-FDG PET/CT) performed before and after concurrent chemoradiotherapy (CCRT) in esophageal cancer.

Methods:

We analyzed the prognosis of 50 non-metastatic squamous cell esophageal cancer (T1-4N0-2) patients who underwent CCRT with curative intent at Inje University Busan Paik Hospital and Haeundae Paik Hospital from 2009 to 2019. Median total radiation dose was 54 Gy (range 34-66 Gy). Our aim was to investigate the relationship between PET/CT values and prognosis. The primary end point was progression-free survival (PFS).

Results:

The median follow-up period was 9.9 months (range 1.7-85.7). Median baseline maximum standard uptake value (SUVmax) was 14.2 (range 3.2-27.7). After treatment, 29 patients (58%) showed disease progression. The 3-year PFS and overall survival (OS) were 24.2% and 54.5%, respectively. PFS was significantly lower (P = 0.015) when SUVmax of initial PET/CT exceeded 10 (n = 22). However, OS did not reach a significant difference based on maximum SUV (P = 0.282). Small metabolic tumor volume (≤14.1) was related with good PFS (P = 0.002) and OS (P = 0.001). Small total lesion of glycolysis (≤107.3) also had a significant good prognostic effect on PFS (P = 0.009) and OS (P = 0.025). In a subgroup analysis of 18 patients with follow-up PET/CT, the patients with SUV max ≤3.5 in follow-up PET/CT showed longer PFS (P = 0.028) than those with a maximum SUV >3.5.

Conclusion:

Maximum SUV of PET/CT is useful in predicting prognosis of esophageal cancer patients treated with CCRT. Efforts to find more effective treatments for patients at high risk of progression are still warranted.

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.

68Ga-fibroblast activation protein inhibitor PET/CT on gross tumour volume delineation for radiotherapy planning of oesophageal cancer

BACKGROUND AND PURPOSE

To compare ⁶⁸Ga-fibroblast activation protein inhibitor (FAPI) and ¹⁸F-FDG PET/CT in imaging locally advanced oesophageal cancer, and evaluate the potential usefulness of ⁶⁸Ga-FAPI PET/CT on gross target volume (GTV) delineation aimed at radiotherapy planning for oesophageal cancer as compared with contrast-enhanced CT (CE-CT) and ¹⁸F-FDG PET/CT.

MATERIALS AND METHODS

Twenty-one patients with newly diagnosed oesophageal cancer who underwent both ¹⁸F-FDG and ⁶⁸Ga-FAPI PET/CT scans were selected. GTVs of the primary tumours based on CE-CT (GTV_CT), PET/CT, and CE-CT plus PET/CT were delineated. Gross tumour lengths were measured by GTVs and endoscopy and recorded.

RESULTS

The ⁶⁸Ga-FAPI PET showed significantly higher radiotracer uptake than ¹⁸F-FDG PET (median SUVmax 16.71 vs. 11.23; P = 0.002) in the primary tumours. SUV thresholds of FAPI ×20%, 30%, 40%, and FDG ×40% showed similar lesion lengths compared with that in endoscopic examination (P > 0.05). GTV_CT demonstrated the largest volume (median: 48.80 mm³, range: 14.83-162.23 mm³) than PET-based GTVs. For PET/CT-guided complementary contouring of GTV_CT, four patients (19%) were increased by FAPI ×20% and 30%, two patients (9.5%) were increased by FAPI ×40%, and only one patient was increased by FDG ×40%. Furthermore, the volume of GTV based on CE-CT plus FAPI ×20%, 30%, and 40% showed no significant difference with GTV_CT and planning target volume based CE-CT plus FAPI-PET and meets the organ at risk standard.

CONCLUSION

The ⁶⁸Ga-FAPI PET/CT methodology showed favourable tumour-to-background contrast in oesophageal cancer and might provide additional information for target volume delineation and help avoid tumour geographic misses.

[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.

Locoregional Residual Esophageal Cancer after Neo-adjuvant Chemoradiotherapy and Surgery Regarding Anatomic Site and Radiation Target Fields: A Histopathologic Evaluation Study

OBJECTIVE

Neoadjuvant chemoradiotherapy followed by surgery establishes a considerable pathologic complete response (pCR) in EC. The aim was to determine site of residual tumor and its prognostic impact.

SUMMARY BACKGROUND DATA

High rates of residual tumor in the adventitial region even inside the radiation fields will influence current decision-making.

METHODS

We evaluated resection specimens with marked target fields from 151 consecutive EC patients treated with carboplatin/paclitaxel and 41.4Gy between 2009 and 2018.

RESULTS

In radically resected (R0) specimens 19.8% (27/136) had a pCR (ypT0N0) and 14% nearly no response (tumor regression grade: tumor regression grade 4-5). Residual tumor commonly extended in or restricted to the adventitia (43.1%; 47/109), whereas 7.3% was in the mucosa (ypT1a), 16.5% in the submucosa (ypT1b) and 6.4% only in lymph nodes (ypT0N+). Macroscopic residues in R0-specimens of partial responders (tumor regression grade 2-3: N = 90) were found in- and outside the gross tumor volume (GTV) in 33.3% and 8.9%, and only microscopic in- and outside the clinical target volume in 58.9% and 1.1%, respectively. Residual nodal disease was observed proximally and distally to the clinical target volume in 2 and 5 patients, respectively. Disease Free Survival decreased significantly if macroscopic tumor was outside the GTV and in ypT2-4aN+.

CONCLUSIONS

After neoadjuvant chemoradiotherapy, pCR and ypT1aN0 were seen in a limited number of R0 resected specimens (19.8% and 7.3%, respectively), whereas 6.4% had only nodal disease (yT0N+). Disease Free Survival decreased significantly if macroscopic residue was outside the GTV and in responders with only nodal disease. Therefore, we should be cautious in applying wait and see strategies.

Subclinical Lesions of the Primary Clinical Target Volume Margin in Esophageal Squamous Cell Carcinoma and Association With FDG PET/CT

Background and Objectives: An accurate delineation of the primary clinical target volume (CTVp) in esophageal squamous cell carcinoma (ESCC) significantly affects the outcomes of radiotherapy. However, when basing the CTVp on the primary gross tumor volume, there are no consistent guidelines for the size of the margin. We compared preoperative ¹⁸F-fluorodeoxyglucose (FDG) PET/CT images and large slices of resected pathological ESCC specimens for evidence and prediction of subclinical lesions. We also investigated associations between the maximum standardized uptake value (SUVmax), metabolic tumor volumes (MTVs), and lesions to improve estimates of the CTVp.

Methods:55 patients underwent FDG PET/CT before surgery, and the SUVmax and MTVs were determined. To ensure that the in situ distances between the primary and secondary tumors were preserved, the esophageal specimens collected during radical surgery were processed to minimize shrinkage, and subclinical lesions were characterized by pathological examination. A 2-dimensional logistic regression model was used to assess the associations between clinicopathological features and microscopic spread of the lesions.

Results: Subclinical lesions in pathological specimens were characterized as direct invasion, multicentric occurrence lesions, intra-mural metastasis, vascular invasion, and perineural invasion in 56.4, 40.0, 30.9, 21.8, and 18.2% of patients, respectively. The mean distances of the subclinical lesions from the primary tumor were 0.79 ± 1.28 cm and 0.87 ± 1.00 cm in the cranial and caudal directions, respectively. Together the SUVmax and MTV values could predict the presence of subclinical lesions that were not detectable in PET/CT images.

Conclusions: To cover 94.5% of ESCC subclinical lesions in the CTVp, a 3-cm margin along the cranial-caudal axis should be added to the primary gross tumor volume as defined by FDG-PET/CT, as well as a cutoff SUVmax value of 2.5. Although preoperative FDG PET/CT images may not reveal lesions directly, the SUVmax and MTV measurements together could predict their presence.

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

•

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

•

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

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PET significantly influences the delineated GTV in oesophageal cancer.

•

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

•

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.

Accurate FDG PET tumor segmentation using the peritumoral halo layer method: a study in patients with esophageal squamous cell carcinoma

Background

In a previous study, FDG PET tumor segmentation (SegPHL) using the peritumoral halo layer (PHL) was more reliable than fixed threshold methods in patients with thyroid cancer. We performed this study to validate the reliability and accuracy of the PHL method in patients with esophageal squamous cell carcinomas (ESCCs), which can be larger and more heterogeneous than thyroid cancers.

Methods

A total of 121 ESCC patients (FDG avid = 85 (70.2%); FDG non-avid = 36 (29.8%)) were enrolled in this study. In FDG avid ESCCs, metabolic tumor length (ML) using SegPHL (ML_PHL), fixed SUV 2.5 threshold (ML_2.5), and fixed 40% of maximum SUV (SUVmax) (ML_40%) were measured. Regression and Bland-Altman analyses were performed to evaluate associations between ML, endoscopic tumor length (EL), and pathologic tumor length (PL). A comparison test was performed to evaluate the absolute difference between ML and PL. Correlation with tumor threshold determined by the PHL method (PHL tumor threshold) and SUVmax was evaluated.

Results

ML_PHL, ML_2.5, and ML_40% correlated well with EL (R² = 0.6464, 0.5789, 0.3321, respectively; p < 0.001) and PL (R² = 0.8778, 0.8365, 0.6266, respectively; p < 0.001). However, ML_2.5 and ML_40% showed significant proportional error with regard to PL; there was no significant error between ML_PHL and PL. ML_PHL showed the smallest standard deviation on Bland-Altman analyses. The absolute differences between ML and PL were significantly smaller for ML_PHL and ML_40% than for ML_2.5 (p < 0.0001). The PHL tumor threshold showed an inverse correlation with SUVmax (σ = − 0.923, p < 0.0001).

Conclusions

SegPHL was more accurate than fixed threshold methods in ESCC. The PHL tumor threshold was adjusted according to SUVmax of ESCC.

PET imaging in adaptive radiotherapy of gastrointestinal tumors

INTRODUCTION

Radiotherapy is a cornerstone in the multimodality treatment of several gastrointestinal (GI) tumors. Positron-emission tomography (PET) has an established role in the diagnosis, response assessment and (re-)staging of these tumors. Nevertheless, the value of PET in adaptive radiotherapy remains unclear. This review focuses on the role of PET in adaptive radiotherapy, i.e. during the treatment course and in the delineation process.

EVIDENCE ACQUISITION

The MEDLINE database was searched for the terms ("Radiotherapy"[Mesh] AND "Positron-Emission Tomography"[Mesh] AND one of the site-specific keywords, yielding a total of 1710 articles. After abstract selection, 27 papers were identified for esophageal neoplasms, 1 for gastric neoplasms, 9 for pancreatic neoplasms, 6 for liver neoplasms, 1 for biliary tract neoplasms, none for colonic neoplasms, 15 for rectal neoplasms and 12 for anus neoplasms.

EVIDENCE SYNTHESIS

The use of PET for truly adaptive radiotherapy during treatment for GI tumors has barely been investigated, in contrast to the potential of the PET-defined metabolic tumor volume for optimization of the target volume. The optimized target definition seems useful for treatment individualization such as focal boosting strategies in esophageal, pancreatic and anorectal cancer. Nevertheless, for all GI tumors, further investigation is needed.

CONCLUSIONS

In general, too little data are available to conclude on the role of PET imaging during radiotherapy for ART strategies in GI cancer. On the other hand, based on the available evidence, the use of biological imaging for target volume adaptation seems promising and could pave the road towards individualized treatment strategies.

Total FDG lesion number on PET/CT predicts survival of esophageal carcinoma patients with recurrence following curative surgery

BACKGROUND

Total lesion number is a prognostic determinant in recurrent esophageal cancer, but this requires multiple tests. Here, we investigated the prognostic value of total FDG lesion number obtained from a single PET/CT study.

METHODS

Subjects were 153 esophageal squamous cell carcinoma patients with loco-regional or distant recurrence following curative surgery. FDG PET/CT performed within 30 days was inspected for abnormal FDG uptake lesions using a SUVmax of 3.0 as threshold for significance. Prognostic associations were assessed by Cox proportional hazards regression and Kaplan-Meier analysis.

RESULTS

PET/CT showed significant local FDG lesions in 49.0%, regional lesions in 78.4%, and distant lesions in 44.4% of patients. Among 73 patients with loco-regional recurrence, 54 had 0-3 and 19 had ≥4 FDG lesions. Among 80 patients with distant recurrence, 31 had 0-3 and 49 had ≥4 FDG lesions. During a median follow-up of 11.8 months, 99 deaths occurred. Univariate variables associated with poor survival included ≥4 FDG lesions and no treatment for loco-regional recurrence and no treatment for distant recurrence. Kaplan Meier analysis showed worse survival for ≥4 than 0-3 FDG lesions in patients with loco-regional recurrence (15.6 vs. 32.1 months; P=0.009), but not in those with distant recurrence. Significant independent predictors of poor survival were ≥4 FDG lesions and no treatment for loco-regional recurrence and no treatment for distant recurrence.

CONCLUSIONS

Total FDG lesion number assessed by PET/CT is a significant independent prognostic factor in esophageal cancer patients with loco-regional recurrence following curative surgery.

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.

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.

Effect of different segmentation algorithms on metabolic tumor volume measured on 18F-FDG PET/CT of cervical primary squamous cell carcinoma

Background and purpose

It is known that fluorine-18 fluorodeoxyglucose PET/computed tomography (CT) segmentation algorithms have an impact on the metabolic tumor volume (MTV). This leads to some uncertainties in PET/CT guidance of tumor radiotherapy. The aim of this study was to investigate the effect of segmentation algorithms on the PET/CT-based MTV and their correlations with the gross tumor volumes (GTVs) of cervical primary squamous cell carcinoma.

Materials and methods

Fifty-five patients with International Federation of Gynecology and Obstetrics stage Ia∼IIb and histologically proven cervical squamous cell carcinoma were enrolled. A fluorine-18 fluorodeoxyglucose PET/CT scan was performed before definitive surgery. GTV was measured on surgical specimens. MTVs were estimated on PET/CT scans using different segmentation algorithms, including a fixed percentage of the maximum standardized uptake value (20∼60% SUV_max) threshold and iterative adaptive algorithm. We divided all patients into four different groups according to the SUV_max within target volume. The comparisons of absolute values and percentage differences between MTVs by segmentation and GTV were performed in different SUV_max subgroups. The optimal threshold percentage was determined from MTV_20%∼MTV_60%, and was correlated with SUV_max. The correlation of MTV_{iterative adaptive} with GTV was also investigated.

Results

MTV_50% and MTV_60% were similar to GTV in the SUV_max up to 5 (P>0.05). MTV_30%∼MTV_60% were similar to GTV (P>0.05) in the 5<SUV_max≤10 group. MTV_20%∼MTV_60% were similar to GTV (P>0.05) in the 10<SUV_max≤15 group. MTV_20% and MTV_30% were similar to GTV (P>0.05) in the SUV_max of at least 15 group. MTV_{iterative adaptive} was similar to GTV in both total and different SUV_max groups (P>0.05). Significant differences were observed among the fixed percentage method and the optimal threshold percentage was inversely correlated with SUV_max. The iterative adaptive segmentation algorithm led to the highest accuracy (6.66±50.83%). A significantly positive correlation was also observed between MTV_{iterative adaptive} and GTV (Pearson’s correlation r=0.87, P<0.0001).

Conclusion

MTV_{iterative adaptive} is independent of SUV_max, more accurate, and correlated with GTV. Iterative adaptive algorithm segmentation may be more suitable than the fixed percentage threshold method to estimate the tumor volume of cervical primary squamous cell carcinoma.

The impact of intratumoral metabolic heterogeneity on postoperative recurrence and survival in resectable esophageal squamous cell carcinoma

OBJECTIVE

To evaluate the impact of intratumoral metabolic heterogeneity measured by 18F-FDG PET imaging on postoperative recurrence and survival for patients with esophageal squamous cell carcinoma (ESCC).

RESULTS

AUC-CSH, metabolic tumor volume and pN-stage were significant prognostic factors for RFS. Additionally, tumor recurrence of the low AUC-CSH group (≤ 0.478) was 3 times higher than high group (P = 0.015). The median OS of patients with advanced AJCC stage or low AUC-CSH was also significantly shorter than that of patients with stage I & II or high AUC-CSH (P = 0.021, 0.009). Multivariate analysis identified the AUC-CSH to be the only significant risk factor for postoperative recurrence and overall survival in whole-group and stage III patients.

MATERIALS AND METHODS

116 ESCC patients who underwent staging 18F-FDG PET-CT scan and surgical resection were reviewed. The metabolic parameters were assessed as follows: maximum standardized uptake value (SUVmax), metabolic tumor volume, and the area under the curve of the cumulative SUV-volume histogram (AUC-CSH), which is known to reflect the intratumoral metabolic heterogeneity. Regression analyses were used to identify clinicopathological and imaging variables associated with relapse-free survival (RFS) and overall survival (OS).

CONCLUSIONS

Intratumoral metabolic heterogeneity characterized by AUC-CSH can predict postoperative recurrence and survival in patients with resectable ESCC.

A Dirichlet process mixture model for automatic (18)F-FDG PET image segmentation: Validation study on phantoms and on lung and esophageal lesions

PURPOSE

The aim of this study was to implement a Dirichlet process mixture (DPM) model for automatic tumor edge identification on (18)F-fluorodeoxyglucose positron emission tomography ((18)F-FDG PET) images by optimizing the parameters on which the algorithm depends, to validate it experimentally, and to test its robustness.

METHODS

The DPM model belongs to the class of the Bayesian nonparametric models and uses the Dirichlet process prior for flexible nonparametric mixture modeling, without any preliminary choice of the number of mixture components. The DPM algorithm implemented in the statistical software package R was used in this work. The contouring accuracy was evaluated on several image data sets: on an IEC phantom (spherical inserts with diameter in the range 10-37 mm) acquired by a Philips Gemini Big Bore PET-CT scanner, using 9 different target-to-background ratios (TBRs) from 2.5 to 70; on a digital phantom simulating spherical/uniform lesions and tumors, irregular in shape and activity; and on 20 clinical cases (10 lung and 10 esophageal cancer patients). The influence of the DPM parameters on contour generation was studied in two steps. In the first one, only the IEC spheres having diameters of 22 and 37 mm and a sphere of the digital phantom (41.6 mm diameter) were studied by varying the main parameters until the diameter of the spheres was obtained within 0.2% of the true value. In the second step, the results obtained for this training set were applied to the entire data set to determine DPM based volumes of all available lesions. These volumes were compared to those obtained by applying already known algorithms (Gaussian mixture model and gradient-based) and to true values, when available.

RESULTS

Only one parameter was found able to significantly influence segmentation accuracy (ANOVA test). This parameter was linearly connected to the uptake variance of the tested region of interest (ROI). In the first step of the study, a calibration curve was determined to automatically generate the optimal parameter from the variance of the ROI. This "calibration curve" was then applied to contour the whole data set. The accuracy (mean discrepancy between DPM model-based contours and reference contours) of volume estimation was below (1 ± 7)% on the whole data set (1 SD). The overlap between true and automatically segmented contours, measured by the Dice similarity coefficient, was 0.93 with a SD of 0.03.

CONCLUSIONS

The proposed DPM model was able to accurately reproduce known volumes of FDG concentration, with high overlap between segmented and true volumes. For all the analyzed inserts of the IEC phantom, the algorithm proved to be robust to variations in radius and in TBR. The main advantage of this algorithm was that no setting of DPM parameters was required in advance, since the proper setting of the only parameter that could significantly influence the segmentation results was automatically related to the uptake variance of the chosen ROI. Furthermore, the algorithm did not need any preliminary choice of the optimum number of classes to describe the ROIs within PET images and no assumption about the shape of the lesion and the uptake heterogeneity of the tracer was required.

A comparative study of target volumes based on 18F-FDG PET-CT and ten phases of 4DCT for primary thoracic squamous esophageal cancer

Purpose

To investigate the correlations in target volumes based on ¹⁸F-FDG PET/CT and four-dimensional CT (4DCT) to detect the feasibility of implementing PET in determining gross target volumes (GTV) for tumor motion for primary thoracic esophageal cancer (EC).

Methods

Thirty-three patients with EC sequentially underwent contrast-enhanced 3DCT, 4DCT, and ¹⁸F-FDG PET-CT thoracic simulation. The internal gross target volume (IGTV)₁₀ was obtained by combining the GTV from ten phases of 4DCT. The GTVs based on PET/CT images were defined by setting of different standardized uptake value thresholds and visual contouring. The difference in volume ratio, conformity index (CI), and degree of inclusion (DI) between IGTV₁₀ and GTV_PET was compared.

Results

The images from 20 patients were suitable for further analysis. The optimal volume ratio of 0.95±0.32, 1.06±0.50, 1.07±0.49 was at standardized uptake value (SUV)_2.5, SUV_20%, or manual contouring. The mean CIs were from 0.33 to 0.54. The best CIs were at SUV_2.0 (0.51±0.11), SUV_2.5 (0.53±0.13), SUV_20% (0.53±0.12), and manual contouring (0.54±0.14). The mean DIs of GTV_PET in IGTV₁₀ were from 0.60 to 0.90, and the mean DIs of IGTV₁₀ in GTV_PET ranged from 0.35 to 0.78. A negative correlation was found between the mean CI and different SUV (P=0.000).

Conclusion

None of the PET-based contours had both close spatial and volumetric approximation to the 4DCT IGTV₁₀. Further evaluation and optimization of PET as a tool for target identification are required.

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.

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

Background

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

Conclusions

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

[Prognostic value of the metabolically active tumour volume]

PURPOSE

The purpose of this study was to assess the prognostic value of different parameters on pretreatment fluorodeoxyglucose [((18)F)-FDG] positron emission tomography-computed tomography (PET-CT) in patients with localized oesophageal cancer.

PATIENTS AND METHOD

We retrospectively reviewed 83 cases of localised oesophageal cancer treated in our institution. Patients were treated with curative intent and have received chemoradiotherapy alone or followed by surgery. Different prognostic parameters were correlated to survival: cancer-related factors, patient-related factors and parameters derived from PET-CT (maximum standardized uptake value [SUV max], metabolically active tumor volume either measured with an automatic segmentation software ["fuzzy locally adaptive bayesian": MATVFLAB] or with an adaptive threshold method [MATVseuil] and total lesion glycolysis [TLGFLAB and TLGseuil]).

RESULTS

The median follow-up was 21.8 months (range: 0.16-104). The median overall survival was 22 months (95% confidence interval [95%CI]: 15.2-28.9). There were 67 deaths: 49 associated with cancer and 18 from intercurrent causes. None of the tested factors was significant on overall survival. In univariate analysis, the following three factors affected the specific survival: MATVFLAB (P=0.025), TLGFLAB (P=0.04) and TLGseuil (P=0.04). In multivariate analysis, only MATVFLAB had a significant impact on specific survival (P=0.049): MATVFLAB<18 cm(3): 31.2 months (95%CI: 21.7-not reached) and MATVFLAB>18 cm(3): 20 months (95%CI: 11.1-228.9).

CONCLUSION

The metabolically active tumour volume measured with the automatic segmentation software FLAB on baseline PET-CT was a significant prognostic factor, which should be tested on a larger cohort.

A new method for segmentation of FDG PET metabolic tumour volume using the peritumoural halo layer and a 10-step colour scale. A study in patients with papillary thyroid carcinoma

AIM

We observed a layer between tumour activity and background on FDG PET/CT with the 10-step colour scale and the window level set properly. We named the layer peritumoral halo layer (PHL). We performed this study to establish the reliability of metabolic tumor volume (MTV) segmentation using PHL (MTV(PHL)) in patients with papillary thyroid carcinoma.

PATIENTS, METHODS

Of a total of 140 papillary thyroid carcinoma (PTC) patients, 70 (50.0%) had FDG-avid PTC. In these patients, MTV(PHL), MTV segmented according to fixed 50% SUVmax (MTV(50%)), and fixed SUV with 2.5 to 4.0 (MTV(2.5) to MTV(4.0)) were compared with pathologic tumour volume (PTV). The absolute percentage difference between MTV(PHL) and PTV was compared in micropapillary carcinoma (MPTC) and non-micropapillary carcinoma (non-MPTC) subgroups. The % SUVmax and SUV thresholds of MTV(PHL) were compared with tumour SUVmax.

RESULTS

Among the MTVs, MTV(50%) was not correlated with PTV (r = -0.16, p = 0.182) and was not reliable according to the Bland-Altman plot. Although MTV(2.5), MTV(3.0), MTV(3.5), and MTV(4.0) correlated with PTV (r = 0.85, 0.86, 0.87, and 0.87, respectively; p < 0.001), these MTVs were not reliable on Bland-Altman analyses. MTV(PHL) was significantly correlated with PTV (r = 0.80, p < 0.001), and the Bland-Altman plot did not show systemic error. The MTV(PHL) was more accurate in non-MPTC than in MPTC (p < 0.001), and the absolute % difference was smaller as PTV became larger (σ = -0.65, p < 0.001). The MTV(PHL) thresholds had correlations with SUVmax (% SUVmax threshold: σ = -0.87, p < 0.001; SUV threshold: r = 0.88, p < 0.001).

CONCLUSIONS

MTV(PHL) was more reliable than MTV(%SUVmax) or MTV(SUV). The reliability of MTV(PHL) improved with larger PTVs. The threshold of the MTV(PHL) was naturally altered by PHL according to SUVmax.

Pattern of Lymphatic Spread of Esophageal Cancer at the Cervicothoracic Junction Based on the Tumor Location : Surgical Treatment of Esophageal Squamous Cell Carcinoma of the Cervicothoracic Junction

BACKGROUND

There is no consensus about the extent of lymphadenectomy for patients with esophageal squamous cell carcinoma at the cervicothoracic junction (CT-ESCC). The purpose of this study was to examine the pattern of lymph node spread in patients with CT-ESCC and the extent of lymphadenectomy that is necessary.

METHODS

We included 64 consecutive patients with CT-ESCC who underwent surgery. All patients were divided into two groups based on the location of the epicenter or anal edge of the primary tumor. Using the height of the epicenter, 27 and 37 patients were classified as having cervical-centered and thoracic-centered tumors, respectively; while, using the height of the anal edge, 38 and 26 patients had tumors that were cervical-localized and thoracic-invading, respectively.

RESULTS

In the patients with cervical-centered tumors, the incidences of metastasis and/or recurrences in the cervical paraesophageal, supraclavicular, and upper mediastinal nodes were 21.4-28.5 %. No patient had metastasis or recurrence in the middle and lower mediastinal and perigastric nodes. In patients with thoracic-centered tumors, the lymph node metastasis and/or recurrence spread to the cervical paraesophageal (41.7 %), supraclavicular (25 %), and upper mediastinal (55.6 %) nodes, as well as the middle (22.2 %) and lower mediastinal (8.3 %) and perigastric (19.4 %) nodes. There was no difference in the distribution and incidence of lymphatic spread between patients with the cervical-localized and thoracic-invading classifications.

CONCLUSIONS

Our results indicate a cervical and upper mediastinal lymphadenectomy is better indicated for patients with cervical-centered CT-ESCC, whereas patients with thoracic-centered CT-ESCC should be treated with a three-field lymphadenectomy.

Utility of baseline 18FDG-PET/CT functional parameters in defining prognosis of primary mediastinal (thymic) large B-cell lymphoma

18FDG PET/CT is a very important staging tool for patients with PMBCL. Metabolic activity defined by TLG on the baseline PET scan is a powerful predictor of PMBCL outcome.

[Are extensive fields useful for radiotherapy of esophageal cancer?]

PURPOSE

Study of the pattern of relapse for locally advanced oesophageal cancer and analysis of the local recurrences according to irradiated volume.

PATIENTS AND METHODS

We performed a monocentric retrospective study of patients treated in the integrated centre of oncology (Angers, France). Two treatment strategies were used: concurrent chemoradiation alone or followed by surgery. Recurrences were classified as: locoregional, either isolated or associated with distant metastasis, and metastatic only. Locoregional relapses were subclassified as in-field, out-field, or mixed.

RESULTS

Between March 2004 and October 2011, 168 patients were treated: 130 by chemoradiation, and 38 by chemoradiation followed by surgery. The median supero-inferior margins added to the gross tumour volume in order to create the planning tumour volume was 5cm (range: 0.5-21). Sixty-two percent of patients (n=104) relapsed: 82 locoregional relapses (49%), including 45 isolated relapses (27%) and 37 associated with distant metastasis relapses (22%), and 22 metastatic relapses (13%). From the 82 locoregional relapses, only four isolated relapses were exclusively out-field.

CONCLUSION

With 5cm supero-inferior margins added to gross tumour volume, less than 3% of patients had an isolated out-field recurrence. However, half of the patients suffered in-field local recurrence and one third had metastases. These findings advocate for a limited prophylactic nodal irradiation. Trials are ongoing to assess dose escalation or surgery in order to increase local control.

Utility of PET for Radiotherapy Treatment Planning

PET imaging has contributed substantially in oncology by allowing improved clinical staging and guiding appropriate cancer management. Integration with radiotherapy planning via PET/computed tomography (CT) simulation enables improved target delineation, which is paramount for conformal radiotherapy techniques. This article reviews the present literature regarding implications of PET/CT for radiotherapy planning and management.

Gradient-based delineation of the primary GTV on FLT PET in squamous cell cancer of the thoracic esophagus and impact on radiotherapy planning

Background

To validate a gradient-based segmentation method for gross tumor volume(GTV) delineation on ⁸F-fluorothymidine (FLT)positron emission tomography (PET)/ computer tomography (CT) in esophageal squamous cell cancer through pathologic specimen, in comparison with standardized uptake values (SUV) threshold-based methods and CT. The corresponding impact of this GTV delineation method on treatment planning was evaluated.

Methods and materials

Ten patients with esophageal squamous cell cancer were enrolled. Before radical surgery, all patients underwent FLT-PET/CT. GTVs were delineated by using four methods. GTV_GRAD, GTV_1.4 and GTV_30%max were segmented on FLT PET using a gradient-based method, a fixed threshold of 1.4 SUV and 30% of SUV_max, respectively. GTV_CT was based on CT data alone. The maximum longitudinal tumor length of each segmented GTV was compared with the measured tumor length of the pathologic gross tumor length (L_Path). GTV_GRAD, GTV_1.4 and GTV_30%max were compared with GTV_CT by overlap index. Two radiotherapy plannings (plan_GRAD) and (plan_CT) were designed for each patient based on GTV_GRAD and GTV_CT. The dose-volume parameters for target volume and normal tissues, CI and HI of plan_GRAD and plan_CT were compared.

Results

The mean ± standard deviation of L_Path was 6.47 ± 2.70 cm. The mean ± standard deviation of L_GRAD,L_1.4, L_30%max and L_CT were 6.22 ± 2.61, 6.23 ± 2.80, 5.95 ± 2.50,7.17 ± 2.28 cm, respectively. The Pearson correlation coefficients between L_Path and each segmentation method were 0.989, 0.920, 0.920 and 0.862, respectively. The overlap indices of GTV_GRAD, GTV_1.4, GTV_30%max when compared with GTV_CT were 0.75 ± 0.12, 0.71 ± 0.12, 0.57 ± 0.10, respectively. The V₅, V₁₀, V₂₀, V₃₀ and mean dose of total-lung,V₃₀ and mean dose of heart of plan_GRAD were significantly lower than plan_CT.

Conclusions

The gradient-based method provided the closest estimation of target length. The radiotherapy plannings based on the gradient-based segmentation method reduced the irradiated volume of lung, heart in comparison to CT.

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.

Simultaneous modulated accelerated radiation therapy for esophageal cancer: A feasibility study

AIM: To establish the feasibility of simultaneous modulated accelerated radiation therapy (SMART) in esophageal cancer (EC).

METHODS: Computed tomography (CT) datasets of 10 patients with upper or middle thoracic squamous cell EC undergoing chemoradiotherapy were used to generate SMART, conventionally-fractionated three-dimensional conformal radiotherapy (3DCRT) and intensity-modulated radiation therapy (cf-IMRT) plans, respectively. The gross target volume (GTV) of the esophagus, positive regional lymph nodes (LN), and suspected lymph nodes (LN±) were contoured for each patient. The clinical target volume (CTV) was delineated with 2-cm longitudinal and 0.5- to 1.0-cm radial margins with respect to the GTV and with 0.5-cm uniform margins for LN and LN(±). For the SMART plans, there were two planning target volumes (PTVs): PTV66 = (GTV + LN) + 0.5 cm and PTV54 = CTV + 0.5 cm. For the 3DCRT and cf-IMRT plans, there was only a single PTV: PTV60 = CTV + 0.5 cm. The prescribed dose for the SMART plans was 66 Gy/30 F to PTV66 and 54 Gy/30 F to PTV54. The dose prescription to the PTV60 for both the 3DCRT and cf-IMRT plans was set to 60 Gy/30 F. All the plans were generated on the Eclipse 10.0 treatment planning system. Fulfillment of the dose criteria for the PTVs received the highest priority, followed by the spinal cord, heart, and lungs. The dose-volume histograms were compared.

RESULTS: Clinically acceptable plans were achieved for all the SMART, cf-IMRT, and 3DCRT plans. Compared with the 3DCRT plans, the SMART plans increased the dose delivered to the primary tumor (66 Gy vs 60 Gy), with improved sparing of normal tissues in all patients. The D_max of the spinal cord, V₂₀ of the lungs, and D_mean and V₅₀ of the heart for the SMART and 3DCRT plans were as follows: 38.5 ± 2.0 vs 44.7 ± 0.8 (P = 0.002), 17.1 ± 4.0 vs 25.8 ± 5.0 (P = 0.000), 14.4 ± 7.5 vs 21.4 ± 11.1 (P = 0.000), and 4.9 ± 3.4 vs 12.9 ± 7.6 (P = 0.000), respectively. In contrast to the cf-IMRT plans, the SMART plans permitted a simultaneous dose escalation (6 Gy) to the primary tumor while demonstrating a significant trend of a lower irradiation dose to all organs at risk except the spinal cord, for which no significant difference was found.

CONCLUSION: SMART offers the potential for a 6 Gy simultaneous escalation in the irradiation dose delivered to the primary tumor of EC and improves the sparing of normal tissues.

Positron Emission Tomography (PET) in Oncology

Since its introduction in the early nineties as a promising functional imaging technique in the management of neoplastic disorders, FDG-PET, and subsequently FDG-PET/CT, has become a cornerstone in several oncologic procedures such as tumor staging and restaging, treatment efficacy assessment during or after treatment end and radiotherapy planning. Moreover, the continuous technological progress of image generation and the introduction of sophisticated software to use PET scan as a biomarker paved the way to calculate new prognostic markers such as the metabolic tumor volume (MTV) and the total amount of tumor glycolysis (TLG). FDG-PET/CT proved more sensitive than contrast-enhanced CT scan in staging of several type of lymphoma or in detecting widespread tumor dissemination in several solid cancers, such as breast, lung, colon, ovary and head and neck carcinoma. As a consequence the stage of patients was upgraded, with a change of treatment in 10%-15% of them. One of the most evident advantages of FDG-PET was its ability to detect, very early during treatment, significant changes in glucose metabolism or even complete shutoff of the neoplastic cell metabolism as a surrogate of tumor chemosensitivity assessment. This could enable clinicians to detect much earlier the effectiveness of a given antineoplastic treatment, as compared to the traditional radiological detection of tumor shrinkage, which usually takes time and occurs much later.

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.

Estimate of the impact of FDG-avidity on the dose required for head and neck radiotherapy local control

Background and purpose

Although FDG-avid tumors are recognized as a potential target for dose escalation, there is no clear basis for selecting a boost dose to counter this apparent radioresistance. Using a novel analysis method, based on the new concept of an outcome-equivalent dose, we estimate the extra dose required to equalize local control between FDG-avid and non-avid head and neck tumors.

Materials and methods

Based on a literature review, five reports of head and neck cancer (423 patients in total), along with an internal validation dataset from our institution (135 oropharynx patients), were used in this analysis. To compensate for the heterogeneity among multi-institutional patient cohorts and corresponding treatment techniques, local control data of the cohorts were fit to a single dose–response curve with a clinically representative steepness (γ₅₀ = 2), thereby defining an ‘outcome-equivalent dose’ (OED) for each institutional cohort. Separate dose–response curves were then determined for the FDG-avid and FDG-non-avid patient cohorts, and the ratio of TD₅₀ (tumor dose required for 50% of control) values between the high- and low-FDG-uptake groups (TD_50,high/TD_50,low) was estimated, resulting in an estimated metabolic dose-modifying factor (mDMF) due to FDG-avidity.

Results

For individual datasets, the estimated mDMFs were found to be in the range of 1.07–1.62, decreasing if the assumed slope (γ₅₀) increased. Weighted logistic regression for the six datasets resulted in a mDMF of 1.19 [95% CI: 1.04–1.34] for a γ₅₀ value of 2, which translates to a needed dose increase of about 1.5 Gy per unit increase in the maximum standardized uptake value (SUV_m) of FDG-PET [95% CI: 0.3–2.7]. Assumptions of lower or higher γ₅₀ values (1.5 or 2.5) resulted in slightly different mDMFs: 1.26 or 1.15, respectively. A validation analysis with seven additional datasets, based on relaxed criteria, was consistent with the estimated mDMF.

Conclusions

We introduced a novel outcome-equivalent dose analysis method to estimate the dose– response modifying effect of FDG uptake variation. To reach equal response rates, FDG-avid tumors are likely to require 10% to 30% more dose than FDG-non-avid tumors. These estimates provide a rational starting point for selecting IMRT boosts for FDG-avid tumors. However, independent tests and refinements of the estimated dose-modifying effect, using high-quality prospective clinical trial data, are needed.

PET/CT planning during chemoradiotherapy for esophageal cancer

PURPOSE

To evaluate the usefulness of positron emission tomography/computed tomography (PET/CT) for field modification during radiotherapy in esophageal cancer.

MATERIALS AND METHODS

We conducted a retrospective study on 33 patients that underwent chemoradiotherapy (CRT). Pathologic findings were squamous cell carcinoma in 32 patients and adenocarcinoma in 1 patient. All patients underwent PET/CT scans before and during CRT (after receiving 40 Gy and before a 20 Gy boost dose). Response evaluation was determined by PET/CT using metabolic tumor volume (MTV), total glycolytic activity (TGA), MTV ratio (rMTV) and TGA ratio (rTGA), or determined by CT. rMTV and rTGA were reduction ratio of MTV and TGA between before and during CRT, respectively.

RESULTS

Significant decreases in MTV (MTV2.5: mean 70.09%, p < 0.001) and TGA (TGA2.5: mean 79.08%, p<0.001) were found between before and during CRT. Median rMTV2.5 was 0.299 (range, 0 to 0.98) and median rTGA2.5 was 0.209 (range, 0 to 0.92). During CRT, PET/CT detected newly developed distant metastasis in 1 patient, and this resulted in a treatment strategy change. At a median 4 months (range, 0 to 12 months) after completion of CRT, 8 patients (24.2%) achieved clinically complete response, 11 (33.3%) partial response, 5 (15.2%) stable disease, and 9 (27.3%) disease progression. SUVmax (p = 0.029), rMTV50% (p = 0.016), rMTV75% (p = 0.023) on intra-treatment PET were found to correlate with complete clinical response.

CONCLUSION

PET/CT during CRT can provide additional information useful for radiotherapy planning and offer the potential for tumor response evaluation during CRT. rMTV50% during CRT was found to be a useful predictor of clinical response.

Determination of an optimal standardized uptake value of fluorodeoxyglucose for positron emission tomography imaging to assess pathological volumes of cervical cancer: a prospective study

Purpose

To determine the optimal standardized uptake value (SUV) of ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) for positron emission tomography (PET) imaging, at which the PET-defined gross tumor volume (GTV_PET) best matches with the pathological volume (GTV_PATH) in the cervical cancer.

Materials and Methods

Ten patients with the cervical cancer who underwent surgery were enrolled in this study. The excised specimens were processed for whole-mount serial sections and H-E staining. The tumor borders were outlined in sections under a microscope, histopathological images were scanned and the GTV_PATH calculated. The GTV_PET was delineated automatically by using various percentages relative to the maximal SUV and absolute SUV. The optimal threshold SUV was further obtained as the value at which the GTV_PET best matched with the GTV_PATH.

Results

An average of 85±10% shrinkage of tissue was observed after the formalin fixation. The GTV_PATH was 13.38±2.80 cm³ on average. The optimal threshold on percentile SUV and absolute SUV were 40.50%±3.16% and 7.45±1.10, respectively. The correlation analysis showed that the optimal percentile SUV threshold was inversely correlated with GTV_PATH (p<0.05) and tumor diameter (p<0.05). The absolute SUV was also positively correlated with SUV_max (p<0.05).

Conclusion

The pathological volume could provide the more accurate tumor volume. The optimal SUV of FDG for PET imaging by use of GTV_PATH as standard for cervical cancer target volume delineation was thus determined in this study, and more cases are being evaluated to substantiate this conclusion.

Improved longitudinal length accuracy of gross tumor volume delineation with diffusion weighted magnetic resonance imaging for esophageal squamous cell carcinoma

BACKGROUND

To analyze the longitudinal length accuracy of gross tumor volume (GTV) delineation with diffusion weighted magnetic resonance imaging for esophageal squamous cell carcinoma (SCC).

METHODS

Forty-two patients from December 2011 to June 2012 with esophageal SCC who underwent radical surgery were analyzed. Routine computed tomography (CT) scan, T2-weighted MRI and diffusion weighted magnetic resonance imaging (DWI) were employed before surgery. Diffusion-sensitive gradient b-values were taken at 400, 600, and 800 s/mm2. Gross tumor volumes (GTV) were delineated using CT, T2-weighted MRI and DWI on different b-value images. GTV longitude length measured using the imaging modalities listed above was compared with pathologic lesion length to determine the most accurate imaging modality. CMS Xio radiotherapy planning system was used to fuse DWI scans and CT images to investigate the possibility of delineating GTV on fused images.

RESULTS

The differences between the GTV length according to CT, T2-weighted MRI and pathology were 3.63 ± 12.06 mm and 3.46 ± 11.41 mm, respectively. When the diffusion-sensitive gradient b-value was 400, 600, and 800 s/mm2, the differences between the GTV length using DWI and pathology were 0.73 ± 6.09 mm, -0.54 ± 6.03 mm and -1.58 ± 5.71 mm, respectively. DWI scans and CT images were fused accurately using the radiotherapy planning system. GTV margins were depicted clearly on fused images.

CONCLUSIONS

DWI displays esophageal SCC lengths most precisely when compared with CT or regular MRI. DWI scans fused with CT images can be used to improve accuracy to delineate GTV in esophageal SCC.