Applications of PET in lung cancer

Hypermetabolic Pulmonary and Mediastinal Lesions With Elevated Cancer Antigen (CA) 15-3 and CA 27-29 in a Patient With a History of Ovarian and Breast Cancer

Breast cancer affects around 13% of women. Breast cancer gene 1 (BRCA1) carriers are prone to lung and lymph node metastasis, while breast cancer gene 2 (BRCA2) carriers tend to have bone metastasis. Findings of pulmonary nodules, mediastinal lymphadenopathy, and elevated markers such as cancer antigen (CA) 15-3 and CA 27-29 suggest metastatic disease. Here, we present the case of a patient with BRCA1-positive breast cancer in remission and a history of ovarian cancer with mediastinal lymphadenopathy and pulmonary nodules, with avid fluorodeoxyglucose uptake on positron emission tomography (PET) scan and elevated CA 15-3 and CA 27-29. A 70-year-old female with a history of bilateral breast and ovarian cancer and a positive BRCA test presented with pulmonary nodules, mediastinal lymphadenopathy, and elevated CA 15-3 and CA 27-29. Imaging showed mediastinal and hilar lymphadenopathy. A PET scan revealed increased metabolic activity in the lymph nodes and pulmonary lesions. Fiberoptic bronchoscopy and endobronchial ultrasound lymph node sampling demonstrated granulomatous inflammation without malignant cells. The patient underwent a therapeutic trial of steroids with clinical improvement of symptoms and decreased hypermetabolic activity in chest lesions, as well as a decrease in tumor markers. The coexistence of sarcoidosis and breast cancer is rare; sarcoidosis can coexist, precede, or appear after breast cancer. In both conditions, tumor markers and PET avidity are seen, which makes diagnosis and management challenging. In case of ambiguity, biopsy is crucial. This case underscores the importance of integrating clinical, pathological, and imaging data to reach an accurate diagnosis and consider a therapeutic trial of steroids. Furthermore, the early PET response to treatment can be pivotal in differentiating between sarcoidosis and malignancy, especially in complex clinical scenarios. Proper differentiation is paramount to avoid therapeutic missteps and ensure appropriate patient management.

Deep learning-based dynamic PET parametric Ki image generation from lung static PET

OBJECTIVES

PET/CT is a first-line tool for the diagnosis of lung cancer. The accuracy of quantification may suffer from various factors throughout the acquisition process. The dynamic PET parametric K_i provides better quantification and improve specificity for cancer detection. However, parametric imaging is difficult to implement clinically due to the long acquisition time (~ 1 h). We propose a dynamic parametric imaging method based on conventional static PET using deep learning.

METHODS

Based on the imaging data of 203 participants, an improved cycle generative adversarial network incorporated with squeeze-and-excitation attention block was introduced to learn the potential mapping relationship between static PET and K_i parametric images. The image quality of the synthesized images was qualitatively and quantitatively evaluated by using several physical and clinical metrics. Statistical analysis of correlation and consistency was also performed on the synthetic images.

RESULTS

Compared with those of other networks, the images synthesized by our proposed network exhibited superior performance in both qualitative and quantitative evaluation, statistical analysis, and clinical scoring. Our synthesized K_i images had significant correlation (Pearson correlation coefficient, 0.93), consistency, and excellent quantitative evaluation results with the K_i images obtained in standard dynamic PET practice.

CONCLUSIONS

Our proposed deep learning method can be used to synthesize highly correlated and consistent dynamic parametric images obtained from static lung PET.

KEY POINTS

• Compared with conventional static PET, dynamic PET parametric K_i imaging has been shown to provide better quantification and improved specificity for cancer detection. • The purpose of this work was to develop a dynamic parametric imaging method based on static PET images using deep learning. • Our proposed network can synthesize highly correlated and consistent dynamic parametric images, providing an additional quantitative diagnostic reference for clinicians.

Pre-Processing Method for Contouring the Uptake Levels of [18F] FDG for Enhanced Specificity of PET Imaging of Solitary Hypermetabolic Pulmonary Nodules

BACKGROUND

The paper presents a pre-processing method which, based on positron-emission tomography (PET) images of ¹⁸F-fluorodeoxyglucose ([18F] FDG) hypermetabolic pulmonary nodules, makes it possible to obtain additional visual characteristics and use them to enhance the specificity of imaging.

MATERIAL AND METHODS

A retrospective analysis of 69 FDG-PET/CT scans of solitary hypermetabolic pulmonary nodules (40 cases of lung cancer and 29 benign tumours), where in each case, the standardised uptake value of the hottest voxel within the defined volume of interest was greater than 2.5 (SUVmax > 2.5). No diagnosis could be made based on these SUVmax values. All of the PET DICOM images were transformed by means of the pre-processing method for contouring the uptake levels of [18F] FDG (PCUL-FDG). Next, a multidimensional comparative analysis was conducted using a synthetic variable obtained by calculating the similarities based on the generalised distance measure for non-metric scaling (GDM2) from the pattern object. The calculations were performed with the use of the R language.

RESULTS

The PCUL-FDG method revealed 73.9% hypermetabolic nodules definitively diagnosed as either benign or malignant lesions. As for the other 26.1% of the nodules, there was uncertainty regarding their classification (some had features suggesting malignancy, while the characteristics of others made it impossible to confirm malignancy with a high degree of certainty).

CONCLUSIONS

Application of the PCUL-FDG method enhances the specificity of PET in imaging solitary hypermetabolic pulmonary nodules. Images obtained using the PCUL-FDG method can serve as point of departure for automatic analysis of PET data based on convolutional neural networks.

Pancreatic FDG uptake on follow-up PET/CT in patients with cancer

To evaluate the breakdown of unexpected pancreatic ¹⁸F-fluorodeoxyglucose (FDG) uptake and the proportion of secondary primary pancreatic cancer on follow-up, patients with cancer underwent positron emission tomography/computed tomography (PET/CT). The participants consisted of 4,473 consecutive patients with cancer who underwent follow-up PET/CT between January 2015 and March 2019 at Kochi Medical School. Among the participants, 225 with a history of pancreatic cancer were excluded from the present study. Retrospective and blinded PET/CT evaluations of 4,248 patients were performed. In patients with pancreatic FDG uptake, the distribution of FDG uptake in the pancreas was evaluated. The final diagnosis was determined pathologically. A total of 14 (0.3%) of the 4,248 patients exhibited FDG uptake in the pancreatic area. Pancreatic abnormalities were detected in 14 patients, and included five cases of pancreatic metastases (36%), four cases of secondary primary pancreatic cancer (29%), two cases of lymph node metastases (14%), one case of malignant lymphoma (7%), one case of autoimmune pancreatitis (7%) and one case of pseudolesion (7%). One patient with early-stage secondary primary pancreatic cancer had a maximum standardized uptake value (SUV_max) <3.0. The remaining 13 patients had a SUV_max >3.0 in the pancreas. Of the 14 patients, two had multiple foci of FDG uptake in the pancreas. Patients with multiple foci of FDG uptake exhibited pancreatic metastasis from renal cell carcinoma and malignant lymphoma. In conclusion, the majority of patients with unexpected pancreatic FDG uptake on follow-up PET/CT exhibited malignancies; furthermore, ~30% of the malignancies detected in patients with pancreatic FDG uptake were secondary primary pancreatic cancers. In patients with unexpected pancreatic FDG uptake on follow-up PET/CT, primary cancer should be considered as well as metastatic tumors.

Integrated strategy combining endobronchial ultrasound with positron emission tomography to diagnose peripheral pulmonary lesions

Background

Endobronchial ultrasound‐guided transbronchial lung biopsy (EBUS‐TBLB) and fluorodeoxyglucose positron emission tomography (FDG‐PET) have been widely used in the diagnosis of peripheral pulmonary lesions (PPLs). This study was conducted to determine the diagnostic value of EBUS‐TBLB combined with FDG‐PET in the assessment of PPLs.

Methods

The clinical data of 76 patients with PPLs who received both FDG‐PET and EBUS‐TBLB from January 2016 to February 2018 were retrospectively evaluated. Further subgroup analysis was performed according to lesion diameter (≤20 mm or >20 mm). Related diagnostic indices were calculated and compared between groups.

Results

When combining EBUS‐TBLB with FDG‐PET, the diagnostic accuracy rate, sensitivity, specificity, Youden's index, positive predictive value, and negative predictive value for PPLs were 86.8%, 90.2%, 73.3%, 63.5%, 93.2%, and 64.7%, respectively. In addition, the diagnostic accuracy rate of the combined approach was significantly higher than the single EBUS‐TBLB and FDG‐PET (P < 0.01 and P < 0.05, respectively), and its Youden's index was also at a higher level. When stratified by lesion diameter, the combined approach showed a significantly higher diagnostic accuracy rate (P < 0.05) and a higher Youden's index for PPLs >20 mm than PPLs ≤20 mm. In addition, we found that positive bronchus sign and probe within the probe were two important factors conducing to enhancing the diagnostic accuracy rate for EBUS‐TBLB.

Conclusions

An integrated approach combining EBUS‐TBLB with FDG‐PET is particularly useful for diagnosing PPLs, and the improved diagnostic yields were especially evident for PPLs >20 mm.

Quantitative volumetric metabolic measurement of solitary pulmonary nodules by F-18 fluorodeoxyglucose positron emission tomography-computed tomography

Background

This study aims to evaluate the effect of quantitative volumetric metabolic measurements in F-18 fluorodeoxyglucose positron emission tomographycomputed tomography to distinguish benign and malignant solitary pulmonary nodules.

Methods

We retrospectively reviewed 78 patients (56 males; 22 females; mean age 61±11.9 years; range, 32 to 82 years) with solitary pulmonary nodules who underwent F-18 fluorodeoxyglucose positron emission tomography-computed tomography. Patients were classified as benign, malignant and metastatic lesions according to pathology results. Metabolic volume, maximum standardized uptake value, mean standardized uptake value, maximum metabolic index and mean metabolic index were measured. Mean, median and standard error values were calculated for each group. Nonparametric tests were used for the comparison of each group. Partial correlation analysis was used for the relationship between parameters. For all parameters, cut-off values were obtained with receiver operating characteristic analysis.

Results

Of 78 lesions, 10 were benign (12.8%), 38 were primary lung carcinoma (48.7%) and 30 were metastatic lung nodules (38.5%). There was a significant difference between benign lesions and primary lung cancer and between primary lung cancer and metastatic groups in all parameters (p<0.05). We determined highly significant positive correlation between maximum standardized uptake value and maximum metabolic index (r=0.73; p<0.05), and moderate positive correlation between mean standardized uptake value and mean metabolic index (r=0.56; p<0.05). In receiver operating characteristic analysis, maximum standardized uptake value and mean standardized uptake value were found to be the most sensitive and specific methods for benign/malignant discrimination. In the cut-off value=2.59, the sensitivity and specificity for maximum standardized uptake value were 98.0% and 91.7%, respectively. In the cut-off value=1.65, the sensitivity and specificity for mean standardized uptake value were 94.0% and 91.7%, respectively.

Conclusion

Maximum metabolic index value is highly correlated with maximum standardized uptake value in benign/malignant solitary pulmonary nodules discrimination by F-18 fluorodeoxyglucose positron emission tomographycomputed tomography. Maximum metabolic index can also be used for discrimination of primary/metastatic malignant lesions.

18F-fluorodeoxyglucose positron emission tomography/computed tomography in the diagnosis of benign pulmonary lesions in sarcoidosis

Background

Many benign pulmonary lesions, especially sarcoidosis, are metabolically active and are indistinguishable from lung cancer using 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) imaging. This study sought to analyze the 18F-FDG PET/CT imaging features of benign pulmonary lesions and to improve the differential diagnosis of benign pulmonary lesions by 18F-FDG PET/CT imaging.

Methods

One hundred and thirteen patients with benign pulmonary lesions were studied retrospectively. Each patient underwent an 18F-FDG PET/CT scan. All cases were identified by pathology, diagnostic therapy or follow-up. The maximum standardized uptake value (SUVmax) was calculated for each pulmonary lesion.

Results

According to the final results, the benign pulmonary lesions were classified as inflammatory lesions (n=77) and granulomas (n=36) by histopathological diagnoses. The SUVmax of inflammatory lesions and granulomas were both high (4.55±2.77 and 6.81±3.96, respectively; P<0.05). When the benign pulmonary lesions were classified by clinical diagnoses, the SUVmax of sarcoidosis was significantly different from other diseases (15.12±5.67; P<0.01).

Conclusions

Inflammatory lesions and granulomas show moderate or high FDG uptake on 18F-FDG PET/CT, but granulomas have higher values. 18F-FDG PET/CT appeared to have a higher SUVmax for the differential diagnosis of sarcoidosis and benign pulmonary lesions.

An overview of PET/MR, focused on clinical applications

Hybrid PET/MR scanners are innovative imaging devices that simultaneously or sequentially acquire and fuse anatomical and functional data from magnetic resonance (MR) with metabolic information from positron emission tomography (PET) (Delso et al. in J Nucl Med 52:1914-1922, 2011; Zaidi et al. in Phys Med Biol 56:3091-3106, 2011). Hybrid PET/MR scanners have the potential to greatly impact not only on medical research but also, and more importantly, on patient management. Although their clinical applications are still under investigation, the increased worldwide availability of PET/MR scanners, and the growing published literature are important determinants in their rising utilization for primarily clinical applications. In this manuscript, we provide a summary of the physical features of PET/MR, including its limitations, which are most relevant to clinical PET/MR implementation and to interpretation. Thereafter, we discuss the most important current and emergent clinical applications of such hybrid technology in the abdomen and pelvis, both in the field of oncologic and non-oncologic imaging, and we provide, when possible, a comparison with clinically consolidated imaging techniques, like for example PET/CT.

A follow-up analysis of positron emission tomography/computed tomography in detecting hidden malignancies at the time of diagnosis of membranous nephropathy

Membranous nephropathy (MN) is the most common kidney disease reported in a variety of malignant diseases. Search for an occult malignancy in MN has presented special challenges. 124 MN patients with a physical examination not suspicious for cancer underwent screening for an occult malignancy with either 18F-Fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) scanning (n = 49) or conventional screening (n = 75) at the time of diagnosis of MN, and were followed up (median,28 months). 154 patients who refused to undergo any screening were followed up (median, 30 months). In FDG-PET/CT cohort, 5 (10.20%) patients were screened and confirmed as malignancy, in contrast, 1 (1.33%) patient in conventional screening cohort. During follow-up, none of malignancy was detected in FDG-PET/CT cohort, 3(4.05%) patients in conventional screening cohort, and 8(5.19%) patients in no-screening cohort. All 6 cases of cancer were detected at early stages and underwent curative resection, and after the resection, proteinuria decreased. In contrast, 11 cases of cancer detected during follow-up died without any remission of proteinuria. These preliminary data provide the first evidence for a potential cancer surveillance that the malignancy screening either through conventional or by PET-CT at the diagnosis of MN led to an early diagnosis and curative treatment.

Dual-time-point 18F-FDG PET/CT in the diagnosis of solitary pulmonary lesions in a region with endemic granulomatous diseases

OBJECTIVE

Granulomatous diseases (GDs) can be metabolically active and indistinguishable from lung cancer on ¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸F-FDG PET) imaging. Evaluation of solitary pulmonary lesions remains a diagnostic challenge in regions with endemic GD. This study sought to determine the efficacy of dual-time-point (DTP) ¹⁸F-FDG PET/computed tomography (CT) imaging in diagnosing solitary pulmonary lesions from such regions.

METHODS

A total of 50 patients with solitary pulmonary nodules or masses with confirmed histopathological diagnoses underwent DTP ¹⁸F-FDG PET/CT imaging at 1 and 3 h after tracer injection. The maximum standardized uptake value (SUV_max) on early and delayed scans (SUV_1h and SUV_3h, respectively) and retention index (RI) were calculated for each pulmonary lesion. Receiver operating characteristic analysis was performed to evaluate the discriminating validity of the parameters.

RESULTS

There were 37 malignant and 13 benign solitary pulmonary lesions. Eight of the 13 (62 %) benign lesions were GDs. The sensitivity/specificity/accuracy of SUV_1h, SUV_3h and RI were 84/69/80 %, 84/85/84 %, and 81/54/74 %, respectively. SUV_3h had the best diagnostic performance, especially regarding specificity. The values of SUV_1h and SUV_3h were significantly different between malignant lesions and GD, while the RI values of malignant lesions and GD were both high (18.6 ± 19.5 and 18.7 ± 15.3 %, respectively; P = not significant).

CONCLUSION

SUV_3h appeared to improve the diagnostic specificity of ¹⁸F-FDG PET/CT in evaluating solitary pulmonary lesions from regions with endemic GD.

Role of positron emission tomography in lung cancer

The ability to demonstrate tumour foci that are undetected by conventional imaging has resulted in the emergence of positron emission tomography (PET) as a valuable clinical tool in oncology. This article describes the technique and indications for fluorine-18 labelled fluorodeoxyglucose (¹⁸FDG)-PET in lung cancer, demonstrating the high accuracy and cost-effectiveness of ¹⁸FDG-PET in the characterisation of solitary pulmonary nodules and in the pre-operative staging of non-small cell lung cancer. Emerging roles in determination of prognosis, radiotherapy planning, therapy monitoring and diagnosis of recurrence are illustrated.

Diagnostic accuracy of contrast-enhanced computed tomography and positron emission tomography with 18-FDG in identifying malignant solitary pulmonary nodules

Contrast-enhanced computed tomography (CECT) and positron emission tomography with 18-FDG (FDG-PET/CT) are used to identify malignant solitary pulmonary nodules. The aim of the study was to evaluate the accuracy of CECT and FDG-PET/CT in diagnosing the etiology of solitary pulmonary nodule (SPN). Eighty patients with newly diagnosed SPN >8 mm were enrolled. The patients were scheduled for either or both, CECT and FDG-PET/CT. The nature of SPN (malignant or benign) was determined either by its pathological examination or radiological criteria. In 71 patients, the etiology of SPN was established and these patients were included in the final analysis. The median SPN diameter in these patients was 13 mm (range 8-30 mm). Twenty-two nodules (31%) were malignant, whereas 49 nodules were benign. FDG-PET/CT was performed in 40 patients, and CECT in 39 subjects. Diagnostic accuracy of CECT was 0.58 (95% confidence interval [CI] 0.41-0.74). The optimal cutoff level discriminating between malignant and benign SPN was an enhancement value of 19 Hounsfield units, for which the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of CECT were 100%, 37%, 32%, and 100%, respectively. Diagnostic accuracy of FDG-PET/CT reached 0.9 (95% CI 0.76-0.9). The optimal cutoff level for FDG-PET/CT was maximal standardized uptake value (SUV max) 2.1. At this point, the sensitivity, specificity, PPV, and NPV were 77%, 92%, 83%, and 89%, respectively. The diagnostic accuracy of FDG-PET/CT is higher than that of CECT. The advantage of CECT is its high sensitivity and negative predictive value.

Imaging of solitary pulmonary nodule-a clinical review

Current widespread use of cross-sectional imaging has led to exponential rise in detection of solitary pulmonary nodules (SPNs). Whilst large numbers of these are benign 'incidentalomas', lung cancers presenting as SPNs are often early disease, which have good prognosis. Therefore, there is rising demand and expectation for more accurate, non-invasive, diagnostic tests to characterize SPNs, aiming to avoid missed or delayed diagnosis of lung cancer. There are wide differential diagnoses of benign and malignant lesions that manifest as SPNs. On conventional imaging, the morphological features supporting benignity include stable small nodule size, smooth demarcated margins, and calcifications. Lack of significant contrast enhancement is also more suggestive of benign nodules. With improved understanding of tumor biology, for instance neo-vascularization and increased vascular permeability, imaging techniques such as dynamic contrast-enhanced computed tomography (CT) provide details on contrast uptake and wash-out kinetics, which is more closely reflecting the physiological and pathological phenomena. Positron emission tomography (PET) using 18fluorine-fluoro-deoxyglucose ((18)F-FDG) is a well-established functional imaging technique, for which one of the most common indications is differentiating between benign and malignant SPNs. Combined PET-CT integrates the anatomical, morphological and metabolic aspects in a single examination, improving overall diagnostic accuracy. Semi-quantitative analysis in FDG-PET imaging is based on measurement of maximum standardized uptake values (SUVmax). SUVmax analysis may become more useful as an assessment of tumor biology in future risk stratification models for cancers. Dual-time point FDG-PET imaging, dual-energy CT, perfusion CT, magnetic resonance (MR) imaging using dynamic contrast enhancement or diffusion-weighted imaging (DWI) techniques, are among the growing armamentarium for diagnostic imaging of SPNs. Provided there is no unacceptably high procedural or operative risk, tissue diagnosis by resection or percutaneous biopsy of SPN should be advocated in those patients identified as at moderate or high risk of malignancy, based on clinical stratification.

PET-CT evaluation of solitary pulmonary nodules: correlation with maximum standardized uptake value and pathology

PURPOSE

18-fluorine fluorodeoxyglucose ((18)F-FDG) positron emission tomography-computed tomography (PET-CT) has an established role for the characterization of solitary pulmonary nodules (SPN). Visual assessment of nodule morphology, together with maximum standardized uptake value (SUVmax), is used to estimate likelihood of malignancy. We correlated SUVmax value with pathology of SPN and assessed diagnostic accuracy in differentiating malignant from benign nodule, using 2.5 as threshold SUVmax.

METHODS

Retrospective review of PET-CT scans for SPN characterization between April 2008 and June 2011 was performed. Only cases with pathological verification were included.

RESULTS

A total of 641 PET-CTs were performed for SPN characterization and staging; 186 patients (77 males, 109 females) with pathological confirmation were included, and 158 (85 %) nodules were malignant: adenocarcinomas (n = 66), squamous cell carcinomas (n = 40), and metastases (n = 20) were the commonest. 28 lesions (15 %) were benign, including granuloma/chronic inflammation (n = 8), infection (n = 7), and hamartomas (n = 5). Using cutoff SUVmax of 2.5, the accuracy of PET-CT in diagnosing malignant SPN is 81.2 %, with sensitivity 86.7 %, specificity 50 %, PPV 90.7 %, and NPV 40 %. The likelihood of malignancy increases with SUVmax. Nevertheless, even with SUVmax <2.5, there is a 62 % chance that a nodule is malignant.

CONCLUSIONS

Although PET-CT is useful in diagnostic workup of SPN, it cannot replace "gold standard" tissue diagnosis.

FDG PET/CT evaluation of pathologically proven pulmonary lesions in an area of high endemic granulomatous disease

Purpose

The goal of this study is to assess how reliable the threshold maximum standardized uptake value (maxSUV) of 2.5 on positron emission tomography–computed tomography (PET/CT) is for evaluation of solitary pulmonary lesions in an area of endemic granulomatous disease and to consider other imaging findings that may increase the accuracy of PET/CT.

Materials and methods

The staging PET/CT of 72 subjects with solitary pulmonary lesions (nodules (less than 3 cm) or masses (greater than 3 cm)) were retrospectively reviewed. Pathology proven diagnosis from tissue samples was used as the gold standard. Logistic regression was used to assess whether the subject’s age, maxSUV, size of lesion, presence of emphysema, or evidence of granulomatous disease was predictive of malignancy.

Results

Malignant lesions were identified in 84.7 % (61/72) of the 72 subjects. A threshold maxSUV of 2.5 had a sensitivity of 95.1 % (58/61), specificity of 45.5 % (5/11), positive predictive value of 90.6 % (58/64), negative predictive value of 62.5 % (5/8) and an accuracy of 87.5 % (63/72). The false negative rate was 4.9 %, and the false positive rate was 54.5 %. All 3 false negatives were less than or equal to 1.0 cm; however, false positives ranged from 1.1 to 5.6 cm. The false negatives had a mean (SD) maxSUV of 2.0 (0.4), whereas the false positives had a mean (SD) maxSUV of 5.6 (3.0). Emphysema was associated with 1.1 higher odds of malignancy, and evidence of granulomatous disease was associated with 0.34 lower odds of benign disease, however, neither was statistically significant (p = 0.92 and p = 0.31, respectively). Higher maxSUV was significantly associated with increased risk of malignancy (p = 8.3 × 10⁻³). Older age and larger size of lesion were borderline associated with increased risk of malignancy (p = 0.05 and p = 0.07, respectively).

Conclusion

In an area of high endemic granulomatous disease, the PET/CT threshold maxSUV of 2.5 retains a high sensitivity (95.1 %) and positive predictive value (90.6 %) for differentiating benign from malignant pulmonary lesions; however, the specificity (45.5) and negative predictive value (62.5) decrease due to increased false positives. The presence of emphysema and absence of evidence of granulomatous disease increases the probability that a pulmonary lesion is malignant; however, these were not statistically significant.

Autologous mesenchymal stem cell-derived dopaminergic neurons function in parkinsonian macaques

A cell-based therapy for the replacement of dopaminergic neurons has been a long-term goal in Parkinson's disease research. Here, we show that autologous engraftment of A9 dopaminergic neuron-like cells induced from mesenchymal stem cells (MSCs) leads to long-term survival of the cells and restoration of motor function in hemiparkinsonian macaques. Differentiated MSCs expressed markers of A9 dopaminergic neurons and released dopamine after depolarization in vitro. The differentiated autologous cells were engrafted in the affected portion of the striatum. Animals that received transplants showed modest and gradual improvements in motor behaviors. Positron emission tomography (PET) using [11C]-CFT, a ligand for the dopamine transporter (DAT), revealed a dramatic increase in DAT expression, with a subsequent exponential decline over a period of 7 months. Kinetic analysis of the PET findings revealed that DAT expression remained above baseline levels for over 7 months. Immunohistochemical evaluations at 9 months consistently demonstrated the existence of cells positive for DAT and other A9 dopaminergic neuron markers in the engrafted striatum. These data suggest that transplantation of differentiated autologous MSCs may represent a safe and effective cell therapy for Parkinson's disease.

The role of dual time point FDG PET imaging in the evaluation of solitary pulmonary nodules with an initial standard uptake value less than 2.5

AIM

To evaluate the accuracy of dual time point 2-[(18)F]-fluoro-2-deoxy-d-glucose (FDG) positron-emission tomography (PET) imaging in the evaluation of the mildly metabolic solitary pulmonary nodule (SPN) and to assess whether accuracy could be improved by delaying second image acquisition to 180 minutes.

MATERIALS AND METHODS

Fifty-four patients were included in the study. Thirty-six had an SUV(max) <2.5 at 60 min. For these patients, two methods of interpreting the subsequent delayed FDG PET imaging at 180 min were investigated. The first method analysed the SUV(max) of SPNs on delayed imaging, in which an SUV(max) of 2.5 or more was regarded as a criterion for malignancy. The second method was retention index (RI) analysis, in which an increase of 10% or more in SUV(max) between the initial and delayed images, was regarded as an indication of malignancy.

RESULTS

For the group as a whole (n=54), the sensitivity, specificity and accuracy of using an SUV(max) of 2.5 or more as an indication of malignancy at the time of initial image acquisition (60 min) was 58, 89, and 74%, respectively. For SPNs that had an initial SUV(max) <2.5 (n=36), the sensitivity, specificity, and accuracy of using an SUV(max) of 2.5 or more as a criterion for malignancy on the delayed image acquisition (180 min), was 36, 96, and 78% respectively. However, if an RI of >10% was used as a criterion for malignancy between the initial and delayed images, the sensitivity, specificity, and accuracy was 73, 80, and 78%, respectively. These results are similar to a recent paper, where image acquisition occurred at 60 and 120 min post-tracer injection.

CONCLUSION

Dual time point FDG PET imaging with RI analysis, is a useful technique in evaluating SPN with an initial SUV(max) <2.5. Prolonging second image acquisition from 120 to 180 min does not appear to improve the accuracy of this technique. However, given that maximal FDG uptake by lung carcinomas is thought to be in the region of 5h, it may be that improving the accuracy of dual time point FDG PET imaging requires a more significant delay in second image acquisition in this specific subgroup.

Preliminary clinical applications of a device-dedicated whole-body positron emission tomography reconstruction method: impact on standardized uptake values

BACKGROUND

¹⁸F-fluorodeoxyglucose positron emission tomography has proven relevance in oncological diagnosis, staging and follow-up. The standardized uptake value (SUV) is one of the most widely used semi-quantitative criteria in PET imaging. However, factors such as noise and image resolution affect the measurement of the SUV. We reported earlier that a device-dedicated projector [attenuation-weighted ordered-subsets expectation maximization detector response (AW-OSEM DR), based on point-source measurements] introduces less noise than a geometrical model (AW-OSEM).

OBJECTIVE

The aim of this study was to investigate the AW-OSEM DR method's impact on SUV measurements under clinical conditions.

METHODS

We first performed a bias analysis to assess the accuracy of the quantitation for the two reconstruction methods as a function of target size and the number of iterations, with 14 acquisitions of the NEMA IEC/2001 phantom. We then used each method to calculate the maximum and average SUVs, respectively for 32 lesions.

RESULTS

For all spheres and all iterations, the bias was significantly lower with AW-OSEM DR than with AW-OSEM (P=0.012). Moreover, a paired Student's t-test showed significant intermethod differences for maximum SUV and average SUV (both P<0.001) in cancer patients. Conversely, the two methods did not differ significantly in terms of the mean SUV and signal-to-noise ratio calculated in the liver for each patient (P=0.5 and 0.08, respectively).

CONCLUSION

Phantom and patient studies were performed to quantify the effects of AW-OSEM DR on PET images. The phantom study highlighted the fact that our method produces more accurate images in terms of the SUV, which is an essential quality for ensuring correct diagnosis, follow-up and treatment planning.

Long-term observation of auto-cell transplantation in non-human primate reveals safety and efficiency of bone marrow stromal cell-derived Schwann cells in peripheral nerve regeneration

Based on their differentiation ability, bone marrow stromal cells (MSCs) are a good source for cell therapy. Using a cynomolgus monkey peripheral nervous system injury model, we examined the safety and efficacy of Schwann cells induced from MSCs as a source for auto-cell transplantation therapy in nerve injury. Serial treatment of monkey MSCs with reducing agents and cytokines induced their differentiation into cells with Schwann cell properties at a very high ratio. Expression of Schwann cell markers was confirmed by both immunocytochemistry and reverse transcription-polymerase chain reaction. Induced Schwann cells were used for auto-cell transplantation into the median nerve and followed-up for 1year. No abnormalities were observed in general conditions. Ki67-immunostaining revealed no sign of massive proliferation inside the grafted tube. Furthermore, (18)F-fluorodeoxygluocose-positron emission tomography scanning demonstrated no abnormal accumulation of radioactivity except in regions with expected physiologic accumulation. Restoration of the transplanted nerve was corroborated by behavior analysis, electrophysiology and histological evaluation. Our results suggest that auto-cell transplantation therapy using MSC-derived Schwann cells is safe and effective for accelerating the regeneration of transected axons and for functional recovery of injured nerves. The practical advantages of MSCs are expected to make this system applicable for spinal cord injury and other neurotrauma or myelin disorders where the acceleration of regeneration is expected to enhance functional recovery.

Thin-section CT of the mediastinum in preoperative N-staging of non-small cell lung cancer: comparison with FDG PET

PURPOSE

To compare diagnostic capability of preoperative N-staging of lung cancer between thin-section CT of the mediastinum and FDG PET, and 5mm slice thickness CT.

MATERIALS AND METHODS

The subjects were 34 patients with lung carcinoma who were examined by both CT and PET, and subsequently underwent surgery between May 2005 and January 2007. CT was carried out with a 16 detector row helical CT scanner. The raw data were reconstructed into 5 mm slice thickness and 1mm slice thickness (thin-section CT). A total of 251 lymph node stations were retrospectively assessed for the presence of lymph node metastasis with thin-section CT, 5 mm CT and PET. In the interpretations of thin-section CT and 5 mm CT, we employed multi-criteria as follows: nodular calcification and intranodal fat as benign criteria, and short-axis diameter more than 10 mm (size criterion), focal low density other than fat, surrounding fat infiltration and convex margin in hilar lymph nodes, as malignant criteria. On PET, maximum standardized uptake value (SUVmax) of 2.5 or more was used as the criterion of malignancy. Sensitivity and specificity were compared between these examinations using McNemar test.

RESULTS

Sensitivities and specificities of thin-section CT, 5 mm CT and PET were 25%, 25%, 25%, and 97%, 94%, 98%, respectively. The statistical analysis revealed that the specificity of 5 mm CT was significantly lower than those of thin-section CT (p=0.039) and PET (p=0.006), while no difference was present between thin-section CT and PET.

CONCLUSION

Thin-section CT of the mediastinum using multiple criteria was comparable to PET in preoperative N-staging of lung cancer.

Fluorodeoxyglucose positron emission tomography and tumor marker expression in non-small cell lung cancer

OBJECTIVE

The best current noninvasive surrogate for tumor biology is fluorodeoxyglucose positron emission tomography (FDG-PET). Both FDG-PET maximal standardized uptake values and selected tumor markers have been shown to correlate with stage, nodal disease, and survival in non-small cell lung cancer (NSCLC). However, there are limited data correlating FDG-PET with tumor markers. The purpose of this study was to determine the correlation of tumor marker expression with FDG-PET maximal standardized uptake values in NSCLC.

METHODS

FDG-PET maximal standardized uptake values were calculated in patients with NSCLC (n = 149). No patient had induction chemoradiotherapy. Intraoperative NSCLC tissue was obtained and tissue microarrays were created. Immunohistochemical analysis was performed for 5 known NSCLC tumor markers (glucose transporter 1, p53, cyclin D1, epidermal growth factor receptor, and vascular endothelial growth factor). Each tumor marker was assessed independently by two pathologists using common grading criteria. Subgroup analysis based on histologic characteristics and regional nodal status was performed.

RESULTS

FDG-PET correlated with T classification (P < .0001), N stage (P = .002), and greatest tumor dimension (P < .0001). In addition, increasing maximal standardized uptake values correlated with increased expression of glucose transporter 1 (P < .0001) and p53 (P = .04) in adenocarcinoma. Epidermal growth factor receptor expression correlated with maximal standardized uptake values without predilection for histologic subtype (P = .004).

CONCLUSION

FDG-PET maximal standardized uptake values correlate with an increased expression of glucose transporter 1 and p53 in lung adenocarcinoma, but not squamous cell cancer. Future studies attempting to correlate FDG-PET with tumor biology will need to consider the effect of different tumor histologic types.

Improved attenuation correction via appropriate selection of respiratory-correlated PET data

PURPOSE

We propose a respiratory-correlated PET data processing method (called "BH-CT-based") based on breath-hold CT acquisition to reduce the smearing effect and improve the attenuation correction. The resulting images are compared with the ungated PET images acquired using a standard, free-breathing clinical protocol.

METHODS

The BH-CT-based method consisted of a list-mode acquisition with simultaneous respiratory signal recording. An additional breath-hold CT acquisition was also performed in order to define a tissue position from which PET events can be selected. A phantom study featured a 0.5-ml sphere (filled with 18F-fluorodeoxyglucose ((18)F-FDG) solution) pushed onto a rubber balloon (filled with (18)F-FDG solution and iodinated contrast agent). The feasibility of the BH-CT-based method was also assessed in two patients.

RESULTS

In the phantom study, the contrast-to-noise ratios (CNRs) were -1.6 for the Ungated volume and 5.1 for the BH-CT-based volume. For patients, CNRs were higher for BH-CT-based volumes than those for Ungated volumes (17.3 vs. 6.3 and 7.3 vs. 3.8, for patients 1 and 2, respectively). Bias-variance measurements were performed and yielded bias reduction of 40% with BH-CT-based.

CONCLUSION

The application of a BH-CT-based method decreases motion bias in PET images. This method resolves issues related to both PET-to-CT misregistration and erroneous attenuation correction and increases lesion detectability.

Effects of respiration-averaged computed tomography on positron emission tomography/computed tomography quantification and its potential impact on gross tumor volume delineation

PURPOSE

Patient respiratory motion can cause image artifacts in positron emission tomography (PET) from PET/computed tomography (CT) and change the quantification of PET for thoracic patients. In this study, respiration-averaged CT (ACT) was used to remove the artifacts, and the changes in standardized uptake value (SUV) and gross tumor volume (GTV) were quantified.

METHODS AND MATERIALS

We incorporated the ACT acquisition in a PET/CT session for 216 lung patients, generating two PET/CT data sets for each patient. The first data set (PET(HCT)/HCT) contained the clinical PET/CT in which PET was attenuation corrected with a helical CT (HCT). The second data set (PET(ACT)/ACT) contained the PET/CT in which PET was corrected with ACT. We quantified the differences between the two datasets in image alignment, maximum SUV (SUV(max)), and GTV contours.

RESULTS

Of the patients, 68% demonstrated respiratory artifacts in the PET(HCT), and for all patients the artifact was removed or reduced in the corresponding PET(ACT). The impact of respiration artifact was the worst for lesions less than 50 cm(3) and located below the dome of the diaphragm. For lesions in this group, the mean SUV(max) difference, GTV volume change, shift in GTV centroid location, and concordance index were 21%, 154%, 2.4 mm, and 0.61, respectively.

CONCLUSION

This study benchmarked the differences between the PET data with and without artifacts. It is important to pay attention to the potential existence of these artifacts during GTV contouring, as such artifacts may increase the uncertainties in the lesion volume and the centroid location.

Role of flourine-18 fluorodeoxyglucose positron emission tomography in thymic pathology

OBJECTIVE

To evaluate the utilization of positron emission tomography (PET) scan with fluorine-18 fluorodeoxyglucose (FDG) in thymic pathology.

METHODS

Twenty-five consecutive patients with thymic pathology underwent FDG-PET after being evaluated by computed tomography (CT). The indication for CT was myasthenia gravis in 10, anterior mediastinal mass in 7, and recurrent thymic tumor after surgical excision in 8 patients. The results of PET were compared with results obtained by CT, and histopathologic examination of the surgical specimens.

RESULTS

All mediastinal abnormal thymic tissue showed FDG uptakes. FDG-PET managed to differentiate between thymic hyperplasia and thymoma in myasthenia gravis group (n=10) in which CT images were questionable in two patients. There was one case of ectopic thymic tissue which was not diagnosed preoperatively. There were no false-negative results for both CT and FDG-PET in seven patients with thymoma presented as anterior mediastinal mass. However, PET scan predicted thymic carcinoma in one patient. PET was superior to CT scan in localization of recurrent thymoma in two patients, and equal to CT in detecting metastatic lesions in six patients during the follow-up after thymoma excision.

CONCLUSIONS

In myasthenia gravis, selective use of FDG-PET is useful in differentiating thymoma from hyperplasia, especially when CT scan is controversial, but fails to recognize ectopic thymic tissue. FDG-PET may differentiate thymoma from thymic carcinoma. FDG-PET is also useful in follow-up patients, who underwent thymoma excision, when there is suspicion of recurrence or metastasis.

Dual-time point FDG PET imaging in the evaluation of pulmonary nodules with minimally increased metabolic activity

PURPOSE

FDG PET has high accuracy in the evaluation of lung nodules. A standardized uptake value (SUV) > or =2.5 is frequently used as a criterion for malignancy in this setting. However, some malignant nodules have only mild FDG activity with a SUV less than 2.5. Assessment of the etiology of lung nodules with only mild metabolic activity remains difficult. This study was undertaken to compare the accuracy of dual-time point and standard single-time FDG PET imaging in the evaluation of such lung nodules.

METHODS

Four hundred fifty-seven dual-time FDG PET scans for lung nodules were retrospectively analyzed. Among them, 46 met the selection criteria and were included for the final analysis. Five methods of interpreting FDG PET results were compared. These methods included visual analysis for both initial and delayed images; SUV analysis for both initial and delayed images in which a SUV of 2.5 is regarded as criteria for malignancy; and finally, the retention index analysis in which a 10% increase in SUV on the delayed images was regarded as an indication of malignancy.

RESULTS

The lowest accuracies came from the visual and single SUV analysis on the initial images. The visual and single SUV analyses on the delayed images produced increased accuracy. The highest accuracy (84.8%) was obtained when a retention index of more than 10% was used as criteria for malignancy.

CONCLUSION

Dual-time FDG PET imaging has the potential for improving accuracy of a test in the evaluation of lung nodules with only borderline levels of increased metabolic activity.

Comparison of lesion-to-cerebellum uptake ratios and standardized uptake values in the evaluation of lung nodules with 18F-FDG PET

OBJECTIVE

To evaluate the clinical performance of the lesion-to-cerebellum uptake ratio (LCR), a semiquantitative index for differentiating malignant from benign lung nodules with [F]fluorodeoxyglucose positron emission tomography (F-FDG PET).

METHODS

Thirty-six patients (16 females, 20 males; median age, 73 years; range, 41-87 years) with 42 known or suspected malignant lung nodules underwent whole-body PET imaging after an intravenous injection of a mean dose of 543+/-69 MBq (14.7+/-1.9 mCi) of F-FDG. The standardized uptake value (SUV) and the LCR were calculated for each nodule and receiver operating characteristic (ROC) curves were analysed using the ROCKIT 0.9B software package.

RESULTS

Surgical pathology and follow-up with serial computed tomography scans for at least 24 months revealed 18 malignant lung lesions and 24 benign lesions less than 3.0 cm in size. The mean LCR was 0.70+/-0.40 for malignant nodules and 0.23+/-0.12 for benign nodules (P<0.001, two-tailed test). The area under the estimated ROC curve was 0.8660 for SUV data and 0.9197 for LCR data (P=0.2408, two-tailed test).

CONCLUSIONS

The LCR method appears to be a valuable semiquantitative index for the evaluation of malignancy in pulmonary nodules with F-FDG PET, which is simple to perform clinically and does not require accurate measurements of body weight or the residual activity in the syringe utilized for F-FDG injection.

Prognostic value of FDG-PET scan imaging in lymphoma patients undergoing autologous stem cell transplantation

We conducted a retrospective analysis of 50 lymphoma patients (Hodgkin's disease and non-Hodgkin's lymphoma) who had an 18F-fluoro-deoxyglucose positron emission tomography (FDG-PET) scan after at least two cycles of salvage chemotherapy and before autologous stem cell transplantation (ASCT) at our institution. The patients were categorized into FDG-PET negative (N = 32) and positive (N = 18) groups. The median follow-up after ASCT was 19 months (range: 3-59). In the FDG-PET-negative group, the median progression-free survival (PFS) was 19 months (range: 2-59) with 15 (54%) patients without progression at 12 months after ASCT. The median overall survival (OS) for this group was not reached. In the FDG-PET-positive group, the median PFS was 5 months (range: 1-19) with only one (7%) patient without progression at 12 months after ASCT. The median OS was 19 months (range: 1-34). In the FDG-PET-negative group, chemotherapy-resistant patients by CT-based criteria had a comparable outcome to those with chemotherapy-sensitive disease. A positive FDG-PET scan after salvage chemotherapy and prior ASCT indicates an extremely poor chance of durable response after ASCT.

Progress and promise of FDG-PET imaging for cancer patient management and oncologic drug development

2-[(18)F]Fluoro-2-deoxyglucose positron emission tomography (FDG-PET) assesses a fundamental property of neoplasia, the Warburg effect. This molecular imaging technique offers a complementary approach to anatomic imaging that is more sensitive and specific in certain cancers. FDG-PET has been widely applied in oncology primarily as a staging and restaging tool that can guide patient care. However, because it accurately detects recurrent or residual disease, FDG-PET also has significant potential for assessing therapy response. In this regard, it can improve patient management by identifying responders early, before tumor size is reduced; nonresponders could discontinue futile therapy. Moreover, a reduction in the FDG-PET signal within days or weeks of initiating therapy (e.g., in lymphoma, non-small cell lung, and esophageal cancer) significantly correlates with prolonged survival and other clinical end points now used in drug approvals. These findings suggest that FDG-PET could facilitate drug development as an early surrogate of clinical benefit. This article reviews the scientific basis of FDG-PET and its development and application as a valuable oncology imaging tool. Its potential to facilitate drug development in seven oncologic settings (lung, lymphoma, breast, prostate, sarcoma, colorectal, and ovary) is addressed. Recommendations include initial validation against approved therapies, retrospective analyses to define the magnitude of change indicative of response, further prospective validation as a surrogate of clinical benefit, and application as a phase II/III trial end point to accelerate evaluation and approval of novel regimens and therapies.

Target Definition in the Thorax and Central Nervous System

It is the aim of conformal radiotherapy to restrict the high-dose region to the target volume as much as possible, thereby sparing the neighboring healthy tissues. However, to increase the therapeutic range, smaller margins tend to be used. This reduction of safety margins enhances the risk of unsuitable dosage because of mistaken target definition. Central nervous system (CNS) and lung cancers constitute sites that are particularly difficult to irradiate combining a large number of conceptual difficulties, allowing them to be considered as 2 particularly interesting study models. Imaging occupies an increasingly important place in these 2 types of tumors, especially with the development of new radiotherapy techniques. CNS and lung cancers represent an example of clinicopathological correlations. More specifically, CNS cancers represent an excellent model for estimation of new 3-dimensional navigational systems. For lung cancer, there is a combination of ballistic difficulties because of respiratory motion, the number and low tolerance of neighboring organs, and dosimetric difficulties because of the presence of inhomogeneities. This article reviews the main currently accepted criteria of choice justifying the size of gross tumor volume and clinical target volume margins for lung and CNS cancers.

Visual and Semiquantitative Analyses for F-18 Fluorodeoxyglucose PET Scanning in Pulmonary Nodules 1 cm to 3 cm in Size

BACKGROUND

While visual assessment is the simplest way to evaluate positron emission tomography (PET) with fluorodeoxyglucose (FDG), faintly positive nodules are often difficult to evaluate. We performed visual and semiquantitative analyses of pulmonary nodules from 1 to 3 cm in size to determine the optimal method of analysis for PET data, especially for faintly positive nodules on visual assessment.

METHODS

Positron emission tomography data were analyzed for 161 pulmonary nodules from 1 to 3 cm in size (108 malignant and 53 benign nodules). On visual assessment, FDG uptake by the nodules was classified into three grades in comparison with mediastinal blood pool, (ie, definitely positive, faintly positive, and negative). In addition, FDG uptake was measured by the standard uptake value (SUV), the contrast ratio to the contralateral lung (CR-lung), and the contrast ratio to the cerebellum (CR-brain). Cut-off values for each variable were determined from receiver operating characteristics (ROC) curves, and the values were 2.5 for the SUV, 0.4 for the CR-lung, and 0.25 for the CR-brain. Nodules with FDG uptake above these cut-off values were defined as positive in each method.

RESULTS

Visual assessment showed definitely positive for 80 nodules (64 malignant and 16 benign), faintly positive for 22 (17 malignant and 5 benign), and negative for 59 nodules (27 malignant and 32 benign). In the 139 nodules that were definitely positive or negative by visual assessment, there were no significant differences of sensitivity and specificity among the four methods (visual assessment, SUV, CR-lung, and CR-brain). In the 17 malignant nodules that were faintly positive, the SUV did not detect any true-positive nodules, but the CR-lung and CR-brain showed 9 and 5 true-positive nodules, respectively, resulting in a significantly higher sensitivity than the SUV (p < 0.001 and p = 0.02, respectively). Fifteen of 17 faintly positive malignant nodules (88%) were histologically well- or moderately-differentiated adenocarcinoma.

CONCLUSIONS

The semiquantitative methods (SUV, CR-lung, and CR-brain) do not improve the efficacy of visual assessment alone for nodules graded as definitely positive or negative. However, faintly positive nodules on visual assessment should be evaluated by the CR-lung or CR-brain rather than the SUV, and are often differentiated adenocarcinomas.

Using FDG-PET activity as a surrogate for tumor cell density and its effect on equivalent uniform dose calculation

The concept of equivalent uniform dose (EUD) has been suggested as a means to quantitatively consider heterogeneous dose distributions within targets. Tumor cell density/function is typically assumed to be uniform. We herein propose to use 18F-labeled 2-deoxyglucose (FDG) positron emission tomography (PET) tumor imaging activity as a surrogate marker for tumor cell density to allow the EUD concept to include intratumor heterogeneities and to study its effect on EUD calculation. Thirty-one patients with lung cancer who had computerized tomography (CT)-based 3D planning and PET imaging were studied. Treatment beams were designed based on the information from both the CT and PET scans. Doses were calculated in 3D based on CT images to reflect tissue heterogeneity. The EUD was calculated in two different ways: first, assuming a uniform tumor cell density within the tumor target; second, using FDG-PET activity (counts/cm3) as a surrogate for tumor cell density at different parts of tumor to calculate the functional-imaging-weighted EUD (therefore will be labeled fEUD for convenience). The EUD calculation can be easily incorporated into the treatment planning process. For 28/31 patients, their fEUD and EUD differed by less than 6%. Twenty-one of these twenty-eight patients had tumor volumes < 200 cm3. In the three patients with larger tumor volume, the fEUD and EUD differed by 8%-14%. Incorporating information from PET imaging to represent tumor cell density in the EUD calculation is straightforward. This approach provides the opportunity to include heterogeneity in tumor function/metabolism into the EUD calculation. The difference between fEUD and EUD, i.e., whether including or not including the possible tumor cell density heterogeneity within tumor can be significant with large tumor volumes. Further research is needed to assess the usefulness of the fEUD concept in radiation treatment.

Positron emission tomography of incidentally detected small pulmonary nodules

The aim of this study was to assess the value of fluorodeoxyglucose positron emission tomography (FDG PET) imaging of small pulmonary nodules incidentally detected by spiral computed tomography (CT) in a high-risk population. Ten patients (five females, five males, aged 54-72 years) were recruited from an ongoing 4-year placebo controlled intervention study of the effect of inhaled steroids in 300 smokers with moderate to severe chronic obstructive pulmonary disease. The participants received yearly CT scans of the chest. Patients with a negative chest radiograph at the time of inclusion, but with pulmonary nodules indeterminate for malignancy detected by conventional spiral CT on a subsequent scan, were referred for FDG PET. Histological diagnoses were sought for all nodules with FDG uptake or where CT showed that they had grown. Ten patients had pulmonary nodules indeterminate for malignancy (approx. 3.3% of the entire study population). The prevalence of malignancy in this group was 50%. The accuracy of PET was high, in spite of the fact that seven patients had nodules smaller than 15 mm and two patients had bronchoalveolar cell carcinoma. This small prospective study indicates that subsequent assessment with FDG PET of small pulmonary nodules incidentally detected by CT has the potential to minimize the numbers of invasive procedures performed in individuals with a benign pulmonary lesion. FDG PET also increases the possibility of an early diagnosis as compared to the strategy of watchful waiting.

The role of FDG-PET scan in staging patients with nonsmall cell carcinoma

BACKGROUND

To assess the role of flourodeoxyglucose-positron-emission tomography (FDG-PET) scan in staging patients with nonsmall cell lung cancer (NSCLC).

METHODS

We prospectively studied 400 patients with NSCLC. Each patient underwent a computed tomography (CT) scan of the chest and upper abdomen, other conventional staging studies and had a FDG-PET scan within 1 month before surgery. All suspicious N2 lymph nodes by either chest CT or by FDG-PET scan were biopsied. Patients that were N2 and M1 negative underwent pulmonary resection and complete thoracic lymphadenectomy.

RESULTS

The FDG-PET had a higher sensitivity (71% vs 43%, p < 0.001), positive predictive value (44% vs 31%, p < 0.001), negative predictive value (91% vs 84%, p = 0.006), and accuracy (76% vs 68%, p = 0.037) than CT scan for N2 lymph nodes. Similarly, FDG-PET had a higher sensitivity (67% vs 41%, p < 0.001), but lower specificity (78% vs 88%, p = 0.009) than CT scan for N1 lymph nodes. FDG-PET led to unnecessary mediastinoscopy in 38 patients. FDG-PET was most commonly falsely negative in the subcarinal (#7) station and the aortopulmonary window lymph node (#5, #6) stations. It accurately upstaged 28 patients (7%) with unsuspected metastasis and it accurately downstaged 23 patients (6%).

CONCLUSIONS

The FDG-PET scan allows for improved patient selection. It more accurately stages the mediastinum, however there are many false positives lymph nodes and it may be more likely to miss N2 disease in the #5, #6, and #7 stations. A positive FDG-PET scan means a tissue biopsy is indicated in that location.

Positron emission tomography scanning with 2-fluoro-2-deoxy-d-glucose as a predictor of response of neoadjuvant treatment for non-small cell carcinoma

OBJECTIVES

Surgical resection after preoperative chemotherapy in patients with non-small cell lung cancer might only be best for patients who are responders. We compared positron emission tomographic scanning with 2-fluoro-2-deoxy-d-glucose (FDP-PET scanning) with computed tomographic scanning to evaluate their ability to predict this response for the primary tumor, N1 and N2 lymph nodes.

METHODS

All patients with non-small cell lung cancer who had an initial FDP-PET scan staging with tissue biopsy, neoadjuvant chemotherapy, repeat FDP-PET scanning, and repeat biopsies were prospectively studied.

RESULTS

There were 34 patients (24 men; median age, 64 years). Eleven patients had N2 disease, and 7 had N1 disease. Twenty-seven patients received chemotherapy, and 7 patients received chemotherapy and radiation. All but 9 patients underwent resection. Statistical analysis showed FDP-PET scanning to be more specific (P <.0001), to have a higher positive predictive value (P =.0018), and to have a higher negative predictive value (P <.0001) than computed tomographic scanning for predicting residual tumor at the primary site. FDP-PET scanning was more sensitive (P <.0001) and more accurate (P <.0001), had a higher positive predictive value (P <.0001), and had a higher negative predictive value (P =.0002) than computed tomographic scanning for paratracheal nodes (number 2 and 4 lymph nodes). FDP-PET scanning had a higher positive predictive value (P <.0001) than computed tomographic scanning for the other N2 (numbers 5, 6, 7, 8, and 9) lymph nodes.

CONCLUSIONS

Repeat FDP-PET scanning is more specific and has a higher positive predictive value and negative predictive value than computed tomographic scanning for detecting residual tumor in the lung in patients with non-small cell lung cancer who have received preoperative chemotherapy. It is more sensitive and accurate for paratracheal N2 nodes as well. However, there is no significant difference in its detection of N1 lymph nodes.

Staging of recurrent and advanced lung cancer with 18F-FDG PET in a coincidence technique (hybrid PET)

The aim of this study was to evaluate [18F]fluorodeoxyglucose ( F-FDG) imaging of recurrent or inoperable lung cancer using a hybrid positron emission tomography (PET) device of the third generation. Examinations were compared with the results of conventional staging. Thirty-six patients suffering from recurrent or primarily inoperable lung cancer (29 men, seven women; age 64.8+/-12.0 years) were examined using hybrid PET (Marconi Axis gamma-PET ) 60 min after injection of 370 MBq F-FDG. The data obtained were reconstructed iteratively. All patients received a computed tomography (CT) scan using either the spiral or multislice technique. All lesions suspicious for primary or recurrent tumour were verified by biopsy; mediastinal lymph nodes were considered as malignant, when positive histology or a small axis diameter of greater than 1 cm measured with CT in addition to progression of clinical course was found. Distant metastases were diagnosed by CT and bone scintigraphy. Using hybrid PET all lesions showed a focally elevated glucose metabolism. Lymph node involvement of the ipsilateral peribronchial and hilar station (N1) was identified in 24/26 cases (92%), in 26/29 cases (90%) of ipsilateral central manifestation (N2) and in 11/13 (85%) cases of central contralateral or supraclavicular lymphatic infestation (N3). Pulmonary spread in hybrid PET was found in 4/8 cases (50%), whereas mainly lung metastases with a diameter of 1.5 cm and smaller were missed. Pleural involvement diagnosed by CT was verified in 4/5 patients. All four patients with bony metastases in conventional staging also presented with positive findings in hybrid PET (8/9 lesions). Concordance with conventional staging was found in 28/36 of patients (78%). In 4/36 patients (11%) unknown sites of tumour were detected leading to therapeutic consequences in three patients after radiological confirmation. Hybrid PET would have led to an understaging in four cases (11%), resulting theoretically in inefficient treatment in two patients. Hybrid PET for F-FDG imaging in the staging of recurrent or primarily inoperable lung cancer supplied equal (78%) or more information (11%) compared to conventional staging procedures. Using the information of hybrid PET alone, 11% of the patients would have been understaged. We conclude that hybrid PET has the potential for use as an additional staging tool in this subgroup of patients, providing supplementary information compared to conventional staging modalities.

Estudo do metabolismo da glicose na tuberculose pulmonar ativa utilizando a tomografia por emissão de pósitrons (18F-FDG PET)

Os métodos de imagem utilizados na avaliação da tuberculose pulmonar incluem a radiografia e a tomografia computadorizada do tórax. As imagens obtidas pelos métodos de medicina nuclear permitem estudos funcionais e metabólicos dos órgãos de interesse, através do uso de radiofármacos específicos. Alterações do metabolismo da glicose podem ser detectadas pela tomografia por emissão de pósitrons (PET) utilizando-se o 18F-fluorodesoxiglicose (18F-FDG). Essas alterações estão presentes nas doenças neoplásicas, inflamatórias e infecciosas. A tuberculose é uma doença granulomatosa causada pelo Mycobacterium tuberculosis, que se utiliza de glicose como fonte de energia. Objetivo: O estudo do metabolismo da glicose na tuberculose pulmonar através da PET e sua comparação com a tomografia computadorizada de tórax. Material e métodos: Foram avaliados 20 pacientes portadores de tuberculose pulmonar. Todos foram submetidos à PET e à tomografia computadorizada de tórax, em até 30 dias após o início do tratamento. Resultados: Todos os pacientes apresentaram captação positiva do 18F-FDG na PET. Na tomografia computadorizada do tórax, todos os pacientes apresentaram sinais compatíveis com atividade de tuberculose. A sensibilidade dos dois métodos foi de 100%. Houve concordância entre os achados do 18F-FDG PET e da tomografia computadorizada (K = 0,27 e p < 0,001). Conclusões: Concluiu-se, através do 18F-FDG PET, que o metabolismo da glicose está alterado na tuberculose pulmonar e que há concordância com as alterações anatômicas observadas pela tomografia computadorizada do tórax.

Lung tumors evaluated with FDG-PET and dynamic CT: the relationship between vascular density and glucose metabolism

PURPOSE

The aim of the current study was to evaluate the relationship between FDG-PET and dynamic CT in lung tumors.

METHOD

Forty consecutive patients with pulmonary tumors underwent whole-body FDG-PET and contrast-enhanced dynamic CT. The size of tumors was 2.6 +/- 0.2 cm (mean +/- SD) at the largest diameter. The standardized uptake value (SUV) of FDG-PET, peak attenuation (APA), and relative flow (RF) of dynamic CT were evaluated. All patients underwent surgery, and tissue samples were available to be studied. The intratumoral microvessel densities (MVDs) were counted and compared with the radiologic parameters. The duration between radiologic examinations and surgery was within 2 weeks in all patients.

RESULTS

The mean SUV, APA, and RF of lung cancers were significantly higher than those of benign lesions (p < 0.05). The mean APA and RF of lung cancers correlated with mean SUV (APA : r = 0.665, p < 0.0001; RF: r = 0.848, p < 0.05) and mean MVD (APA: r = 0.801, p < 0.0001; RF: r = 0.723, p < 0.05). The mean SUV of lung cancers correlated with the mean MVD (r = 0.612, p < 0.001). No correlation was found between the mean APA, RF, SUV, and MVD in benign tumors.

CONCLUSION

The APA and RF of dynamic CT correlated with the SUV of FDG-PET imaging in lung cancer. The APA and RF of dynamic CT as an index of blood pooling may be related to increased glucose metabolism in lung cancer.

Conformal radiotherapy for lung cancer: different delineation of the gross tumor volume (GTV) by radiologists and radiation oncologists

PURPOSE

Delineation of the gross tumor volume (GTV) and organs at risk constitutes one of the most important phases of conformal radiotherapy (CRT) procedures. In the absence of a clear redefinition of the GTV, for a given pathology, complemented by detailed contouring procedures, the GTV are likely to be estimated rather arbitrarily with the risk of tumor underdosage or detriment to the surrounding healthy tissues. The objective of this study was to compare the delineation of the GTV of intrathoracic tumors by radiologists and radiation oncologists with experience in the field in various centers.

MATERIALS AND METHODS

The computed tomography images of ten patients with nonoperated non-small cell lung cancer (NSCLC) eligible for CRT were reviewed. Nine radiologists and eight radiation oncologists working in five different centers, classified as either 'junior' or 'senior' according to their professional experience, had to delineate the GTV (primary tumor and involved lymph nodes) with predefined visualization parameters. A dedicated software was used to compare the delineated volumes in terms of intersection and union volumes and to calculate the 'concordance index' for each patient and each subgroup of physicians.

RESULTS

Significant differences between physicians and between centers were observed. Compared to radiation oncologists, radiologists tended to delineate smaller volumes and encountered fewer difficulties to delineate 'difficult' cases. Junior physicians, regardless of their specialty, also tended to delineate smaller and more homogeneous volumes than senior physicians, especially for 'difficult' cases.

CONCLUSIONS

Major discordances were observed between the radiation oncologists' and the radiologists' delineations, indicating that this step needs to be improved. A better training of radiation oncologists in thoracic imaging and collaboration between radiation oncologists and radiologists should decrease this variability. New imaging techniques (image fusion, positron emission tomography, magnetic resonance imaging spectroscopy, etc.) may also provide a useful contribution to this difficult delineation.

[Estimation of the probability of mediastinal involvement: a statistical definition of the clinical target volume for 3-dimensional conformal radiotherapy in non-small-cell lung cancer?]

PURPOSE

Conformal irradiation of non-small cell lung carcinoma (NSCLC) is largely based on a precise definition of the nodal clinical target volume (CTVn). The reduction of the number of nodal stations to be irradiated would render tumor dose escalation more achievable. The aim of this work was to design an mathematical tool based on documented data, that would predict the risk of metastatic involvement for each nodal station.

METHODS AND MATERIAL

From the large surgical series published in the literature we looked at the main pre-treatment parameters that modify the risk of nodal invasion. The probability of involvement for the 17 nodal stations described by the American Thoracic Society (ATS) was computed from all these publications and then weighted according to the French epidemiological data. Starting from the primitive location of the tumour as the main characteristic, we built a probabilistic tree for each nodal station representing the risk distribution as a function of each tumor feature. From the statistical point of view, we used the inversion of probability trees method described by Weinstein and Feinberg.

RESULTS

Taking into account all the different parameters of the pre-treatment staging relative to each level of the ATS map brings up to 20,000 different combinations. The first chosen parameters in the tree were, depending on the tumour location, the histological classification, the metastatic stage, the nodal stage weighted in function of the sensitivity and specificity of the diagnostic examination used (PET scan, CAT scan) and the tumoral stage. A software is proposed to compute a predicted probability of involvement of each nodal station for any given clinical presentation.

CONCLUSION

To better define the CTVn in NSCLC 3DRT, we propose a software that evaluates the mediastinal nodal involvement risk from easily accessible individual pre-treatment parameters.

Surgical treatment of stage III non-small cell lung cancer

The resectability of NSCLC is determined by its stage. The surgical treatment in stage I and II NSCLC remains a golden standard. Stage IIIA NSCLC constitutes a non-homogenous group, and many patients are potentially non-resectable. The patients in stage IIIA NSCLC also constitute a non-homogenous group. The patients in stage T3N1 usually undergo surgical resection, but many patients with N2 disease are disqualified from surgical treatment due to the negative prognostic factors. The negative prognostic factors comprise: (1) metastases to upper paratracheal (no 2), anterior paratracheal (no 3), and subcarinal (no 7) lymph nodes; (2) metastases to multiple mediastinal lymph nodes; (3) occurrence of the so called 'bulky disease'; (4) capsular lymph node invasion. The occurrence of one of these negative prognostic factors disqualifies the patient with N2 disease from radical surgical treatment. In more advanced cases, i.e. stage IIIB, and stage IV NSCLC, patients are rarely operated. It regards the patients in stage T4 N1, and in M1 disease with a single metastasis (mainly to CNS) accompanied by the stage I, or II, of the primary focus. In these cases N2 disease always constitutes the contraindication to the surgical treatment. Multidisciplinary approach in the treatment of NSCLC is supposed to improve the results of the treatment of NSCLC.

Localised disease in cancer of unknown primary (CUP): the value of positron emission tomography (PET) for individual therapeutic management

BACKGROUND

Two to four percent of cancer patients present with CUP syndrome. Median survival for localised disease is 20 and for disseminated disease, seven months. For localised disease, curative treatment is more likely and individual therapeutic strategies become more important. After conservative diagnostic procedures including MRI, the primary is detected in less than 25%. The diagnostic value of PET and its influence on therapeutic strategies was evaluated.

PATIENTS AND METHODS

Forty-two patients with localised CUP were investigated from 5 of 98 to 10 of 2000. The presenting site was lymph node metastasis in 34 and visceral metastasis in 8 patients. After a median of 7 (3-11) diagnostic procedures without detection of the primary, but evidence of localised disease, PET was performed with fluorine-18-fluorodeoxyglucose.

RESULTS

In 26 of 42 patients (62%), a primary was suggested by PET and confirmed in 18 (43%). In 5 of 18 patients beyond localised disease, additional dissemination, not detected by previous diagnostic measures, was diagnosed by PET. Overall, dissemination was only detected only by PET in 16 of 42 patients (38%). In29 of 42 patients (69%), the PET result influenced selection of the definitive treatment.

CONCLUSION

In CUP patients, PET has a certain impact on detection of the primary as well as of the disseminated disease. and may also have a certain impact on therapeutic management.