A clinical evaluation of FDG-PET to assess the response in radiation therapy for bronchogenic carcinoma

Metabolic response assessment with 18F-FDG PET/CT: inter-method comparison and prognostic significance for patients with non-small cell lung cancer

OBJECTIVE

This study aimed to (1) compare the agreement of two evaluation methods of metabolic response in patients with non-small cell lung cancer (NSCLC) and determine their prognostic value and (2) explore an optimal cutoff of metabolic reduction to distinguish a more favorable subset of responders.

METHODS

This is a secondary analysis of prospective studies. Enrolled patients underwent 18F-PET/CT within 2 weeks before, during, and months after radiotherapy (post-RT). Metabolic response was assessed using both Peter MacCallum (PM) method of qualitative visual assessment and University of Michigan (UM) method of semiquantitative measurement. The agreement between two methods determined response, and their prediction of outcome was analyzed.

RESULTS

Forty-four patients with median follow-up of 25.2 months were analyzed. A moderate agreement was observed between PM- and UM-based response assessment (Kappa coefficient = 0.434), unveiling a significant difference in CMR rate (p = 0.001). Categorical responses derived from either method were significantly predictive of overall survival (OS) and progression-free survival (PFS) (p < 0.0001). Numerical percentage decrease of FDG uptake also showed significant correlations with survival, presenting a hazard ratio of 0.97 for both OS and PFS. A 75 % of SUV decrease was found to be the optimal cutoff to predict OS and 2-year progression.

CONCLUSIONS

There was a modest discrepancy in metabolic response rates between PM and UM criteria, though both could offer predictive classification for survival. The percentage decrease provides an ordinal value that correlates with prolonged survival, recommending 75 % as the optimal threshold at identifying better responders.

High FDG uptake predicts poorer survival in locally advanced nonsmall cell lung cancer patients undergoing curative radiotherapy, independently of tumor size

OBJECTIVES

Despite radical radiotherapy and chemotherapy (CT), the prognosis of locally advanced nonsmall cell lung cancer (NSCLC) is poor. New prognostic indicators are being looked forward to improve the survival. [18F]-fluorodeoxyglucose (FDG) uptake on PET/CT has been observed as a prognostic marker mainly in early-stage disease. Our aim was to examine the prognostic value of FDG uptake in locally advanced NSCLC.

MATERIALS AND METHODS

Between 2009 and 2011, 103 NSCLC patients underwent disease staging using FDG PET/CT before conformal radiotherapy. Thoracic radiation was administered at a daily fraction of 2 Gy. Total dose was prescribed according to the tumor response against CT. All patients underwent CT. Survival was estimated using the Kaplan-Meier method.

RESULTS

The median age of the patients was 59 years (range 39-83). The median follow-up time was 22.63 months (range 6-48.03 months). There was a statistically significant difference in overall survival (OS) between the low (<10.7) and high (≥10.7) standardized uptake value (SUVmax) groups (p = 0.006) on univariate analysis (3-year OS was 42% in the low (<10.7) and 23% in the high (≥10.7) SUVmax groups). On multivariate analysis with determining tumor size, tumor SUVmax provided additional significant prognostic information on OS (HR 1.046; 95 % CI 1.009-1.085, p = 0.015).

CONCLUSIONS

FDG uptake has predictive value in locally advanced NSCLC, independently of tumor size.

A practical algorithmic approach to the diagnosis and management of solitary pulmonary nodules: part 1: radiologic characteristics and imaging modalities

The solitary pulmonary nodule (SPN) is frequently encountered on chest imaging and poses an important diagnostic challenge to clinicians. The differential diagnosis is broad, ranging from benign granulomata and infectious processes to malignancy. Important concepts in the evaluation of SPNs include the definition, morphologic characteristics via appropriate imaging modalities, and the calculation of pretest probability of malignancy. Morphologic differentiation of SPN into solid or subsolid types is important in the choice of follow-up and further management. In this first part of a two-part series, we describe the morphologic characteristics and various imaging modalities available to further characterize SPN. In Part 2, we will describe the determination of pretest probability of malignancy and an algorithmic approach to the diagnosis of SPN.

Early response to chemotherapy in patients with non-small-cell lung cancer assessed by [18F]-fluoro-deoxy-D-glucose positron emission tomography and computed tomography

BACKGROUND

This study aimed to demonstrate that patients who exhibit a tumor metabolic response to first-line chemotherapy seen on FDG-PET and computed tomography (CT) would survive longer than those who did not show such a response, comparing this evaluation with the morphologic response seen on CT.

PATIENTS AND METHODS

Images were acquired in 22 consecutive patients with advanced non-small-cell lung cancer (NSCLC) randomized to receive carboplatin/paclitaxel/sorafenib or placebo. FDG-PET was performed within 4 weeks before (PET1) and 2 weeks after starting treatment (PET2). Similarly, CT (CT1) was performed at baseline and then every 2 cycles (6 weeks) during treatment (CT2). Responders and nonresponders were identified with FDG-PET, and metabolic response was then compared with morphologic changes detected by spiral CT.

RESULTS

Twenty-one of 22 patients completed this study. In terms of progression-free survival (PFS) (45 vs. 22.2 weeks) and overall survival (OS) (77 vs. 47.7 weeks), we observed a trend that was not statistically significant for patients whose response after 2 weeks of treatment was seen on FDG-PET (P = .22 for PFS; P = .15 for OS).

CONCLUSION

Patients with advanced NSCLC who had a positive outcome, as evidenced by prolonged survival, were those who showed a tumor metabolic response seen on FDG-PET.

Evaluating FDG uptake changes between pre and post therapy respiratory gated PET scans

PURPOSE

Whole body (3D) and respiratory gated (4D) FDG-PET/CT scans performed pre-radiotherapy (pre-RT) and post-radiotherapy (post-RT) were analyzed to investigate the impact of 4D PET in evaluating 18F-fluorodeoxyglucose (FDG) uptake changes due to therapy, relative to traditional 3D PET.

METHODS AND MATERIALS

3D and 4D sequential FDG-PET/CT scans were acquired pre-RT and approximately one month post-RT for patients with non-small cell lung cancer (NSCLC). The lesions of high uptake targeted with radiotherapy were identified on the pre-RT scan of each patient. Each lesion on the 3D and each of the five phases of the 4D scan were analyzed using a region of interest (ROI). For each patient the ROIs of the pre-RT scans were used to locate the areas of initial FDG uptake on the post-RT scans following rigid registration. Post-RT ROIs were drawn and the FDG uptake was compared with that of the pre-RT scans.

RESULTS

Sixteen distinct lesions from 12 patients were identified and analyzed. Standardized uptake value (SUV) maxima were significantly higher (p-value <0.005) for the lesions as measured on the 4D compared to 3D PET. Comparison of serial pre and post-RT scans showed a mean 62% decrease in SUV with the 3D PET scan (range 36-89%), and a 67% decrease with the 4D PET scan (range 30-89%). The mean absolute difference in SUV change on 3D versus 4D scans was 4.9%, with a range 0-15% (p-value = 0.07).

CONCLUSIONS

Signal recovery with 4D PET results in higher SUVs when compared to standard 3D PET. Consequently, differences in the evaluation of SUV changes between pre and post-RT plans were observed. Such difference can have a significant impact in PET-based response assessment.

Functional imaging in predicting response to antineoplastic agents and molecular targeted therapies in lung cancer: a review of existing evidence

The increasing use of FDG-PET ((18)F-2-fluoro-2-deoxy-d-glucose positron emission tomography) imaging in the staging of non-small-cell lung cancer (NSCLC) may result in a significant shift in stage distribution, with an increased percentage of patients staged as having metastatic disease and consequently a higher percentage of patients treated with systemic therapy. The amount of FDG-PET uptake in primary lung lesions has been shown to be correlated with tumour growth rate. Data suggest that tumours with increased glucose uptake are presumably more metabolically active and more biologically aggressive, and standardized uptake value (SUV) at PET may be regarded as a prognostic factor. Growing evidence suggests that PET may be used as a predictive marker to assess the activity of antineoplastic agents, allowing close monitoring of the efficacy of the treatment in order to be able to switch earlier to alternative therapies according to the individual chemosensitivity of the tumour. Currently the value of FDG-PET for monitoring response is complicated by the heterogeneity of the published data on the methods used for FDG quantification and the selection of the primary targets and clinical endpoints. As a result, objective validation of proposed thresholds of responsiveness is lacking. This article discusses the assessment of treatment response in NSCLC patients using functional imaging, and emphasizes advantages and limitations in clinical management.

Detection and characterization of tumor changes in 18F-FDG PET patient monitoring using parametric imaging

In PET-based patient monitoring, metabolic tumor changes occurring between PET scans are most often assessed visually or by measuring only a few parameters (tumor volume or uptake), neglecting most of the image content. We propose and evaluate a parametric imaging (PI) method to assess tumor changes at the voxel level.

METHODS

Seventy-eight pairs of tumor images obtained from baseline and follow-up (18)F-FDG PET/CT for 28 patients with metastatic colorectal cancer were considered. For each pair, after CT-based registration of the PET volumes, the 2 PET datasets were subtracted. A biparametric graph of subtracted voxel values versus voxel values in the first PET scan was obtained. A model-based analysis of this graph was used to identify the tumor voxels in which significant changes occurred between the 2 scans and yielded indices characterizing these changes. The Response Evaluation Criteria in Solid Tumors (RECIST) based on the CT images obtained 5-8 wk after the second PET/CT scan were used to classify tumor masses as responding or progressive. On the basis of this classification, we compared the sensitivity and specificity of PI and an approach based on recommendations from the European Organization for Research and Treatment of Cancer (EORTC).

RESULTS

For tumor-based classification, the EORTC-based approach had a sensitivity and specificity of 85% and 52%, respectively, for detecting responding lesions, whereas PI had a sensitivity and specificity of 100% and 53%, respectively. None of responding tumors using RECIST was classified as progressive with the PI or EORTC-based criteria. Among the 14 progressive lesions according to RECIST, 12 were identified as progressive with PI whereas EORTC-based criteria classified only 1 as progressive and 13 as stable tumors. Considering the patient-based classification, none of the responders according to RECIST was classified as having progressive disease with the PI and EORTC-based criteria. PI has the advantage of showing a parametric image of the patient response to therapy, indicating potential heterogeneity in tumor response.

CONCLUSION

The PI method has been successfully applied to characterize early metabolic tumor changes in 78 lesions from (18)F-FDG PET/CT scans of patients with metastatic colorectal cancer during chemotherapy. The PI findings correlated well with the standard RECIST-based response assessment.

Therapeutic implications of molecular imaging with PET in the combined modality treatment of lung cancer

Molecular imaging with PET, and certainly integrated PET-CT, combining functional and anatomical imaging, has many potential advantages over anatomical imaging alone in the combined modality treatment of lung cancer. The aim of the current article is to review the available evidence regarding PET with FDG and other tracers in the combined modality treatment of locally advanced lung cancer. The following topics are addressed: tumor volume definition, outcome prediction and the added value of PET after therapy, and finally its clinical implications and future perspectives. The additional value of FDG-PET in defining the primary tumor volume has been established, mainly in regions with atelectasis or post-treatment effects. Selective nodal irradiation (SNI) of FDG-PET positive nodal stations is the preferred treatment in NSCLC, being safe and leading to decreased normal tissue exposure, providing opportunities for dose escalation. First results in SCLC show similar results. FDG-uptake on the pre-treatment PET scan is of prognostic value. Data on the value of pre-treatment FDG-uptake to predict response to combined modality treatment are conflicting, but the limited data regarding early metabolic response during treatment do show predictive value. The FDG response after radical treatment is of prognostic significance. FDG-PET in the follow-up has potential benefit in NSCLC, while data in SCLC are lacking. Radiotherapy boosting of radioresistant areas identified with FDG-PET is subject of current research. Tracers other than (18)FDG are promising for treatment response assessment and the visualization of intra-tumor heterogeneity, but more research is needed before they can be clinically implemented.

Four-dimensional positron emission tomography: implications for dose painting of high-uptake regions

PURPOSE

To investigate the behavior of tumor subvolumes of high [18F]-fluorodeoxyglucose (FDG) uptake as seen on clinical four-dimensional (4D) FDG-positron emission tomography (PET) scans.

METHODS AND MATERIALS

Four-dimensional FDG-PET/computed tomography scans from 13 patients taken before radiotherapy were available. The analysis was focused on regions of high uptake that are potential dose-painting targets. A total of 17 lesions (primary tumors and lymph nodes) were analyzed. On each one of the five phases of the 4D scan a classification algorithm was applied to obtain the region of highest uptake and segment the tumor volume. We looked at the behavior of both the high-uptake subvolume, called "Boost," and the segmented tumor volume, called "Target." We measured several quantities that characterize the Target and Boost volumes and quantified correlations between them.

RESULTS

The behavior of the Target could not always predict the behavior of the Boost. The shape deformation of the Boost regions was on average 133% higher than that of the Target. The gross to internal target volume expansion was on average 27.4% for the Target and 64% for the Boost, a statistically significant difference (p < 0.05). Finally, the inhale-to-exhale phase (20%) had the highest shape deformation for the Boost regions.

CONCLUSIONS

A complex relationship between the measured quantities for the Boost and Target volumes is revealed. The results suggest that in cases in which advanced therapy techniques such as dose painting are being used, a close examination of the 4D PET scan should be performed.

A pilot trial of serial 18F-fluorodeoxyglucose positron emission tomography in patients with medically inoperable stage I non-small-cell lung cancer treated with hypofractionated stereotactic body radiotherapy

PURPOSE

Routine assessment was made of tumor metabolic activity as measured by 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) in Stage I non-small-cell lung cancer (NSCLC). This report describes PET correlates prospectively collected after stereotactic body radiotherapy (SBRT) for patients with medically inoperable NSCLC.

METHODS AND MATERIALS

14 consecutive patients with medically inoperable Stage I NSCLC were enrolled. All patients received SBRT to 60-66 Gy in three fractions. Patients underwent serial planned FDG-PET/computed tomography fusion imaging before SBRT and at 2, 26, and 52 weeks after SBRT.

RESULTS

With median follow-up of 30.2 months, no patients experienced local failure. One patient developed regional failure, 1 developed distant failure, and 1 developed a second primary. The median tumor maximum standardized uptake value (SUV(max)) before SBRT was 8.70. The median SUV(max) values at 2, 26, and 52 weeks after SBRT were 6.04, 2.80, and 3.58, respectively. Patients with low pre-SBRT SUV were more likely to experience initial 2-week rises in SUV, whereas patients with high pre-SBRT SUV commonly had SUV declines 2 weeks after treatment (p = 0.036). Six of 13 patients had primary tumor SUV(max) >3.5 at 12 months after SBRT but remained without evidence of local disease failure on further follow-up.

CONCLUSIONS

A substantial proportion of patients may have moderately elevated FDG-PET SUV(max) at 12 months without evidence of local failure on further follow-up. Thus, slightly elevated PET SUV(max) should not be considered a surrogate for local treatment failure. Our data do not support routine serial FDG-PET/computed tomography for follow-up of patients receiving SBRT for Stage I NSCLC.

Predictive and prognostic value of FDG-PET

The predictive and prognostic value of fluorodeoxyglucose (FDG)-positron emission tomography (PET) in non-small-cell lung carcinoma, colorectal carcinoma and lymphoma is discussed. The degree of FDG uptake is of prognostic value at initial presentation, after induction treatment prior to resection and in the case of relapse of non-small cell lung cancer (NSCLC). In locally advanced and advanced stages of NSCLC, FDG-PET has been shown to be predictive for clinical outcome at an early stage of treatment. In colorectal carcinoma, limited studies are available on the prognostic value of FDG-PET, however, the technique appears to have great potential in monitoring the success of local ablative therapies soon after intervention and in the prediction and evaluation of response to radiotherapy, systemic therapy, and combinations thereof. The prognostic value of end-of treatment FDG-PET for FDG-avid lymphomas has been established, and the next step is to define how to use this information to optimize patient outcome. In Hodgkin's lymphoma, FDG-PET has a high negative predictive value, however, histological confirmation of positive findings should be sought where possible. For non-Hodgkin's lymphoma, the opposite applies. The newly published standardized guidelines for interpretation formulates specific criteria for visual interpretation and for defining PET positivity in the liver, spleen, lung, bone marrow and small residual lesions. The introduction of these guidelines should reduce variability among studies. Interim PET offers a reliable method for early prediction of long-term remission, however it should only be performed in prospective randomized controlled trials. Many of the diagnostic and management questions considered in this review are relevant to other tumour types. Further research in this field is of great importance, since it may lead to a change in the therapeutic concept of cancer. The preliminary findings call for systematic inclusion of FDG-PET in therapeutic trials to adequately position FDG-PET in treatment time lines.

Predictive and prognostic value of FDG-PET in nonsmall-cell lung cancer: a systematic review

For several years, molecular imaging with (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET) has become part of the standard of care in presurgical staging of patients with nonsmall-cell lung cancer (NSCLC), focusing on the detection of malignant lesions at early stages, early detection of recurrence, and metastatic spread. Currently, there is an increasing interest in the role of FDG-PET beyond staging, such as the evaluation of biological characteristics of the tumor and prediction of prognosis in the context of treatment stratification and the early assessment of tumor response to therapy. In this systematic review, the literature on the value of the evolving applications of FDG-PET as a marker for prediction (ie, therapy response monitoring) and prognosis in NSCLC is addressed, divided in sections on the predictive value of FDG-PET in locally advanced and advanced disease, the prognostic value of FDG-PET at diagnosis, after induction treatment, and in recurrent disease. Furthermore, the background and recommendations for the application of FDG-PET for these indications will be discussed.

FDG-PET and stereotactic body radiotherapy (SBRT) for stage I non-small-cell lung cancer

PURPOSE

To investigate the utility of positron emission tomography (PET) in patients treated with stereotactic body radiotherapy (SBRT) for stage I non-small-cell lung cancer (NSCLC) on prospective institutional trials.

PATIENTS AND METHODS

Fifty-eight patients with medically inoperable stage I NSCLC who participated in prospective phase I and II trials of SBRT, had >or=2 years of follow-up, and received FDG-PET imaging are the focus of this evaluation. Fifty-seven of 58 patients received pre-SBRT FDG-PET to confirm stage I status. All patients received stereotactic body frame immobilization and treatment with 7-10 photon beams. SBRT total doses ranged from 24 to 72Gy in three fractions. No elective nodal irradiation was undertaken. Regular follow-up with planned CT imaging was performed on all patients. Post-SBRT FDG-PET was not mandated by protocol and was typically ordered upon concern for disease recurrence. Thirty-eight post-SBRT PET studies were performed in 28 patients at a median 17.3 months following SBRT.

RESULTS

With a median follow-up of 42.5 months, the 3-year actuarial overall survival and local control for this select subset of our SBRT experience were 48.9% and 74.8%, respectively. Pre-SBRT FDG-PET SUV did not predict 3-year overall survival or local control. Fourteen of 57 patients eventually failed in nodal stations by CT and/or PET. Isolated first site of failure was nodal in 6 patients (10%). Out of 28 patients with post-SBRT PET, 4 (14%) had delayed PET imaging (22-26 months after SBRT) showing moderate hypermetabolic activity (SUV 2.5-5.07), but no evidence of local, nodal, or distant recurrence by clinical examination and conventional imaging performed 20-26 months following these concerning PET findings.

CONCLUSIONS

Isolated nodal recurrence following PET-staged I NSCLC treated with SBRT is uncommon. Moderate post-SBRT PET hypermetabolic activity may persist 2 years following treatment without definite evidence of recurrence. Further study is needed to confirm these results in larger populations with longer follow-up.

Positron emission tomography imaging in nonsmall-cell lung cancer

Positron emission tomography (PET) using 18F-2-deoxy-D-glucose, a D-glucose analog labeled with fluorine-18, complements conventional radiologic assessment in the evaluation of patients with nonsmall-cell lung cancer (NSCLC). PET is being routinely used to improve the detection of nodal and extrathoracic metastases. PET is also currently being evaluated in the assessment of prognosis and therapeutic response and by potentially allowing an earlier assessment of response may prove invaluable in the oncologic management of patients. The article discusses the diagnosis, staging, and assessment of treatment response and prognosis with an emphasis on the appropriate clinical use of PET in management.

Partnerships in oncology and radiology: the role of radiology in the detection, staging, and follow-up of lung cancer

In this review, I examine the multifaceted role of radiology in the diagnosis, staging, and management of lung cancer, highlighting new applications and modalities such as computer-aided detection of lung nodules and positron emission tomography/computed tomography for staging and monitoring response to therapy. Lung cancer screening is also discussed.

PET/CT Imaging of Lung Cancer

Fluoro-deoxyglucose positron emission tomography (PET) imaging has a diagnostic and prognostic value in the initial staging, restaging, and surveillance of non-small-cell lung cancer (NSCLC). When used in conjunction with conventional radiologic imaging, PET imaging has been shown to result in significant changes in clinical management of NSCLC. Specifically, baseline PET imaging can improve initial staging and guide surgical and radiotherapy planning, whereas repeat PET imaging after the initiation of chemoradiotherapy can predict tumor response and help tailor therapy. After the end of definitive treatment, PET has greater diagnostic accuracy than other imaging modalities for the detection of tumor recurrence. The recent development of fused PET/CT imaging has improved the radiologic evaluation of NSCLC patients by combining metabolic and anatomic imaging; however, this has resulted in more complexity in the image interpretation. It is important for the interpreting physician to understand the role PET/CT plays in the staging, assessment of treatment, and follow-up after therapy in the multidisciplinary management of patients with NSCLC.

Critical review of PET-CT for radiotherapy planning in lung cancer

In the last decade, FDG-PET scans have had a major impact on the treatment of patients with NSCLC. The benefits of staging PET scans are well established, with improved selection of patients for curative radiotherapy or aggressive chemo-radiotherapy. The large body of literature correlating FDG-PET with nodal pathology in NSCLC makes it rational to use PET for designing mediastinal radiation fields. However, suboptimal image-fusion and a low spatial resolution for PET scans, makes use of PET for defining target volumes for primary tumours questionable. Data on the role of PET scans for radiotherapy planning for limited stage small-cell lung cancer is limited, although the incorporation of FDG-PET positive regions would appear to be reasonable.

Functional Imaging in Lung Cancer

Accurate detection of the presence and extent of disease is vital in the management of non–small-cell lung cancer. While computed tomography and magnetic resonance imaging tend to be the routine diagnostic modalities used in the management of lung cancer, there have been significant advances in the field of functional and molecular imaging. In this article, we review the performance of the functional imaging techniques that are currently available for the evaluation of non–small-cell lung cancer. The techniques range from evaluation of glucose metabolism in tumors with fluorodeoxyglucose, to evaluation of proliferation with fluorothymidine and evaluation of tumor hypoxia with agents such as fluoromisonidazole. Magnetic resonance imaging with an emphasis on dynamic contrast enhancement of tumors as well as detecting of malignant lymph nodes with targeted contrast agents is discussed. Emerging technologies such as lung imaging fluorescence endoscopy are considered. The role of functional imaging in planning, predicting response to, and evaluating effects of, various therapies is explored.

Value of F-18-fluorodeoxyglucose positron emission tomography after induction therapy of locally advanced bronchogenic carcinoma

OBJECTIVES

Induction therapy is an important treatment option in locally advanced non-small cell lung cancer. F-18-fluorodeoxyglucose positron emission tomography (FDG-PET) has an important role in initial staging. The aim of this study was to assess the value of FDG-PET in restaging after induction therapy and in analyzing tumor viability, nodal status, distant metastases, and prognosis.

METHODS

Forty-seven patients with locally advanced non-small cell lung cancer accepted for resection after induction therapy underwent FDG-PET. Images were interpreted visually for mediastinal nodal status and metastatic spread. The FDG accumulation in the tumor site was measured by using the maximum standardized uptake value.

RESULTS

Unexpected metastases were detected by means of FDG-PET in 9 patients. Surgical intervention was not performed in 8 patients with confirmed metastases. The rate of unexpected findings increased from complete radiologic remission (0%) over partial remission (9%) to no change (67%). The standardized uptake value was higher in tumors with (n = 26) than in those without (n = 11) histologic proof of viability (6.4 +/- 5.3 vs 2.9 +/- 1.6, P = .006). All patients with standardized uptake values of greater than 5.8 had viable tumors. Sensitivity, specificity, and negative predictive value were 81%, 64%, and 58% for tumor viability and 50%, 88%, and 85% for persistent mediastinal disease. Median survival after resection was greater than 56 months for patients with tumor standardized uptake values of less than 4 and 19 months for patients with standardized uptake values of 4 or greater ( P < .001).

CONCLUSION

FDG-PET helps in the selection of patients for resection after induction therapy. It can be used to detect unexpected distant metastases, especially after poor response to induction therapy. Its high negative predictive value in mediastinal restaging allows for omission of repeat mediastinoscopy. Tumor standardized uptake value after induction is a prognostic factor.

Advances in positron emission tomographic imaging of lung cancer

Positron emission tomography (PET) with [18F]fluorodeoxyglucose (FDG) has been established as a useful tool in the management of patients with non-small cell lung cancer and promises to be as valuable in the clinical management of other cancers. PET imaging with FDG allows the assessment of tumor glucose metabolism in vivo; however, a number of other PET tracers are being used in oncologic research to assess changes in other cellular processes associated with malignant transformation of the cell. [11C]-Labeled methionine and choline are being used to assess changes in cell membrane synthesis; however, small studies have not shown the added information from these tracers to be clinically useful. DNA synthesis can be assessed by measuring the uptake of the thymidine analog 3'-deoxy-3'-[18F]fluorothymidine, which may be more specific for evaluating malignancy without the problem of false-positive results from inflammatory lesions, as seen with FDG. Tumor hypoxia imaging with copper-labeled diacetyl-bis(N(4)-methylthiosemicarbazone) or [18F]fluoromisonidazole may provide a better method of predicting which tumors will respond best to conventional therapy. The role of PET will continue to evolve with further clinical studies using these and other new tracers.

Early FDG-PET imaging after radical radiotherapy for non-small-cell lung cancer: inflammatory changes in normal tissues correlate with tumor response and do not confound therapeutic response evaluation

PURPOSE

To investigate the relationship between positron emission tomography (PET) detected inflammatory changes in irradiated normal tissues and metabolic response at tumor sites in patients receiving radical radiotherapy for non-small-cell lung cancer. The prognostic significance of these changes was also studied.

METHODS

In 73 consecutive patients, (18)F-fluorodeoxyglucose (FDG) PET was performed at a median of 70 days after completion of radical radiotherapy. Radiation-induced inflammatory change was scored for normal tissues within the radiation treatment volume using a 0-3 grading scale. Metabolic tumor response was assessed using a pattern-recognition algorithm comparing pre- and posttreatment scans. Prognostic significance of inflammatory changes was tested using the Cox proportional hazards regression model.

RESULTS

Increased FDG uptake in normal tissues (radiotoxicity) was associated with a greater likelihood of complete or partial tumor response on both PET (p = 0.0044) and computed tomography (p = 0.029). Prognostic stratification provided by PET response was both significant and of a similar magnitude in patients with low- and high-grade radiotoxicity.

CONCLUSION

Postradiotherapy inflammatory changes detected by FDG-PET are positively correlated with tumor response, suggesting that tumor radioresponsiveness and normal tissue radiosensitivity may be linked. Prognostic stratification provided by PET is not compromised by inflammatory changes if a meticulous visual response assessment technique is used.

Positron-emission tomography in prognostic and therapeutic assessment of lung cancer: systematic review

Positron-emission tomography (PET) with 18-fluorodeoxyglucose has a role in the diagnosis and staging of lung cancer, but is also appealing for assessment of prognosis and treatment. A systematic search of the published work shows good evidence that [(18)F]FDG uptake on PET has independent prognostic value in newly diagnosed non-small-cell lung cancer. PET is a sensitive method of measuring the biological effects of anticancer therapy, but until better standardisation and large-scale experience is available, it should only be used for additional assessments of early response in clinical trials. Further studies are needed to define the role of [(18)F]FDG-PET in restaging after induction therapy in multimodality approaches for locally advanced lung cancer. The assessment of prognosis by [(18)F]FDG-PET is less substantiated in treated lung cancer than in newly diagnosed patients. Good prospective evidence documents the effectiveness of [(18)F]FDG-PET over CT in the correct identification of recurrent lung cancer.

The Role of PET Scan in Diagnosis, Staging, and Management of Non‐Small Cell Lung Cancer

Positron emission tomography (PET) is now an important cancer imaging tool, both for diagnosis and staging, as well as offering prognostic information based on response. This report attempts to comprehensively review the value of PET in the locoregional and distant staging of non-small cell lung cancer (NSCLC), illustrate the potential effects on patient management, and give a short overview of newer applications. PET sets the gold standard in the evaluation of an indeterminate solitary pulmonary nodule or mass, where PET has proven to be significantly more accurate than computed tomography (CT) in the distinction between benign and malignant lesions. In the evaluation of metastatic spread to locoregional lymph nodes, PET is significantly more accurate than CT, so that invasive surgical staging may be omitted in many patients with negative mediastinal PET images. In patients with positive mediastinal PET images, invasive surgical staging remains mandatory because of the possibility of false-positive findings due to inflammatory nodes or granulomatous disorders. In the search for metastatic spread, PET is a useful adjunct to conventional imaging. This may be due to the finding of unexpected metastatic lesions or due to exclusion of malignancy in lesions that are equivocal on standard imaging. However, at this time, PET does not replace conventional imaging. Large-scale randomized studies are currently examining whether PET staging will actually improve the appearance of lung cancer outcome.

Value of whole-body FDG PET in management of lung cancer

18F-fluorodeoxyglucose (FDG) PET imaging provides physiologic and metabolic information that characterizes lesions that are indeterminate by CT. FDG PET imaging is sensitive to the detection of lung cancer in patients who have indeterminate lesions on CT, whereas low grade malignancy such as bronchioloalveolar carcinoma and carcinoid may be negative on FDG PET. The specificity of PET imaging is less than its sensitivity because some inflammatory processes, such as active granulomatous infections, avidly accumulate FDG. This possibility should be kept in mind in the analysis of PET studies of glucose metabolism aimed at differentiating malignant from benign solitary pulmonary nodules. FDG uptake is considered to be a good marker of cell differentiation, proliferative potential, aggressiveness, and the grade of malignancy in patients with lung cancer. FDG PET accurately stages the distribution of lung cancer. Several studies have documented the increased accuracy of PET compared with CT in the evaluation of the hilar and mediastinal lymphnode status in patients with lung cancer. Whole-body PET studies detect metastatic disease that is unsuspected by conventional imaging. Management changes have been reported in up to 41% of patients on the basis of the results of whole-body studies. Whole-body FDG PET is also useful for the detection of recurrence. Several studies have indicated that the degree of FDG uptake in primary lung cancer can be used as an independent prognostic factor. Thus, whole-body FDG PET is clinically very useful in the management of lung cancer.

Role of 18FDG-positron emission tomography scanning in the management of histiocytosis

Diagnostic evaluation of histiocytic malignancies often involves a range of imaging studies to characterize skeletal and extraskeletal sites of involvement. Functional imaging with 18FDG PET provides a potential method for non-invasively detecting active disease. We report two cases where this modality was positive and facilitated therapeutic monitoring.

Positron emission tomography in lung cancer

Carcinoma of the lung is one of the most frequent malignancies and a major cause of mortality. The use of positron emission tomography (PET) has been extensively investigated in patients with carcinoma of the lung and has established clinical utility and cost-effectiveness in characterization of solitary pulmonary nodules and preoperative staging of carcinoma of the lung. Evolving applications in carcinoma of the lung include detection of recurrence, assessment of treatment response, radiotherapy planning, and prognosis. In addition, there is developing interest in combined anatomic/metabolic imaging and new tracer techniques, in particular gene expression imaging. This review aims to present existing data supporting the use of PET in carcinoma of the lung and to explore the evolving indications and future prospects of PET and lung cancer.

Discordant response to chemotherapy detected by PET scanning: unveiling of a second primary cancer

Positron emission Tomography (PET) is commonly used to stage malignancies and monitor response to treatment. This report describes two patients, one with metastatic breast cancer and the other with aggressive non-Hodgkin's lymphoma (NHL) whose responses to treatment were monitored by serial computed tomography and PET scans. In both cases after completion of systemic chemotherapy, repeat PET scanning revealed residual metabolically active tissue at the base of the neck. Because of differential therapeutic response, the possibility of different pathologic lesions was raised. In each case, further investigation with an ultrasound scan and needle biopsy revealed carcinoma of the thyroid. Both patients were subsequently treated with definitive surgery. In both described cases, a second primary malignancy was found that affected further management and in the second patient altered prognosis. This report concludes that residual metabolically active tissue on PET scans after treatment is not necessarily resistant primary disease. A mixed response requires further investigation, particularly in the case of persisting solitary abnormalities in the neck.

Positron emission tomography (PET) and combined imaging modalities for staging lung cancer

FDG PET in its current form supplements but does not yet replace other noninvasive imaging modalities for the evaluation and staging of the patient with NSCLC. Clinicians await further data from well-designed clinical trials to help integrate FDG PET into current clinical practice. Looking forward, sophisticated radiolabeling techniques promise to improve both the diagnostic accuracy of PET and our ability to deliver targeted cancer therapy to patients.

Staging of non-small cell lung cancer: consensus, controversies and challenges

Stage is with performance status, the most potent prognostic factor in non-small cell lung cancer. In the past decades, much effort has been directed towards the definition, description, development and implementation of staging guidelines. This has undoubtedly resulted in improvements in therapy and insight in the biology of the disease. The new millennium sees us confronted with an increasing epidemic of lung cancer. Hence, the need for further improvements in staging accuracy and cost effectiveness, in order to use the available therapeutic armament at its best and provide the patient with a treatment that is best adjusted to his or her condition. Current controversies and future challenges in staging will be addressed.

Positron emission tomography (PET) of non-small cell lung cancer

Positron emission tomography (PET) with FDG has shown to be of substantial value in differential diagnosis of pulmonary lesions and in the assessment of lymph node involvement with higher sensitivity and specificity than CT. A negative PET scan of the mediastinum suggests that mediastinoscopy is unnecessary and that these patients can proceed directly to thoracotomy. The method is also useful for the visualization of distant metastases. Since changes of treatment may result after identification of distant metastases PET is also cost-effective [Eur J Nucl Med 27(2000)1598; Australas Radiol 45(2001)9]. Furthermore, changes of tumor metabolism can be detected with PET at early stages after treatment, which can be used for therapy monitoring and for the detection of recurrent tumor tissue after completion of treatment.

Imaging of lung cancer with CT, MRT and PET

The staging of non-small lung cancer has to be performed in an interdisciplinary approach considering all clinical, radiological and histologic results. The staging using imaging procedures is done according to the TNM classification with T describing the extent of the primary tumor, N the presence and location of metastatic lymph nodes and M the presence or absence of distant metastases. It is important to remember that the individual stages of the TNM classification have undergone numerous revisions and thus need to be considered in their most recent version [Chest 111 (1997) 1718; Chest 111 (1997) 1710]. Noninvasive information about the stage of the disease is important for the planning and optimization of therapy. This may be done with imaging procedures such as, CT, MRT or PET.

[Interest in 18-FDG positron emission tomography in radiotherapy planning: example of lung cancer radiotherapy]

18 FDG positon emission tomography provides metabolic images and allows better local and metastatic staging than radiologic methods. A best cartography of node involvement and a best delineation of the tumor zone should allow an optimal radiotherapy. Lung cancer is a good example of the interest of this new method.

The role of positron emission tomography with 18F-fluoro-2-deoxy-D-glucose in respiratory oncology

In the past 5 yrs, positron emission tomography (PET) with 18F-fluoro-2-deoxy-D-glucose (FDG) has become an important imaging modality in lung cancer patients. At this time, the indication of FDG-PET as a complimentary tool to computed tomography in the diagnosis and staging of nonsmall cell lung cancer has gradually gained more widespread acceptance and also reimbursement in many European countries. This review focuses on the data of FDG-PET in the diagnosis of lung nodules and masses, and in locoregional and extrathoracic staging of nonsmall cell lung cancer. Emphasis is put on the potential clinical implementation of the currently available FDG-PET data. The use of FDG-PET in these indications now needs further validation in large-scale multicentre randomized studies, focusing mainly on treatment outcome parameters, survival and cost-efficacy. Interesting findings with 18F-fluoro-2-deoxy-D-glucose-positron emission tomography have also been reported for the evaluation of response to radio- or chemotherapy, in radiotherapy planning, recurrence detection and assessment of prognosis. Finally, a whole new field of application of positron emission tomography in molecular biology, using new radiopharmaceuticals, is under extensive investigation.

CT and (18)F-deoxyglucose (FDG) image fusion for optimization of conformal radiotherapy of lung cancers

PURPOSE

To validate a computed tomography (CT) and (18)F-deoxyglucose (FDG) image fusion procedure and to evaluate its usefulness to facilitate target definition and treatment planning in three-dimensional conformal radiation therapy (3D-CRT) for non-small-cell lung cancer.

METHODS AND MATERIALS

Twelve patients were assessed by CT and FDG-coincidence mode dual-head gamma camera (CDET) before radiotherapy. The patients were placed in a similar position during CT and FDG-CDET. Matching was achieved by minimizing the cost function by 3D translation and rotation between four landmarks drawn on the patient's skin. Virtual simulation was performed from image fusion and estimated dose-volume histograms (DVH) were calculated.

RESULTS

Quantitative analysis indicated that the matching error was < 5 mm. Fusion of anatomic and metabolic data corrected staging of lymph nodes (N) for 4 patients and staging of metastases for 1 patient. In these 5 patients, DVH revealed that the lung volume irradiated at 20 Gy (Vl(20)) was decreased by an average of 22.8%, and tumor volume irradiated at the 95% isodose (V(95)) was increased by 22% and 8% for 2 patients, respectively, and was decreased by an average of 59% for 3 patients after fusion. No difference in terms of Vl(20) and V(95) was observed for the other 7 patients.

CONCLUSION

We have validated CT and FDG-CDET lung image fusion to facilitate determination of lung cancer volumes, which improved the accuracy of 3D-CRT.

Fluorine-18 FDG dual-head gamma camera coincidence imaging of radiation pneumonitis

A 69-year-old man with inoperable stage I squamous cell carcinoma of the lung underwent a radical course of radiotherapy combined with platinum-based chemotherapy. Fluorine-18 fluorodeoxyglucose (FDG) imaging with a dual-head coincidence gamma camera system (Co-PET) diagnosed radiation pneumonitis 1 month after completion of radiotherapy, when the clinical and radiographic signs were atypical and more suggestive of carcinomatous lymphangitis. Treatment with oral steroids was begun based on FDG scan findings, with prompt clinical benefit as would be expected for radiation pneumonitis.

PET imaging in oncology

The role of positron emission tomography (PET) during the past decade has evolved rapidly from a pure research tool to a methodology of enormous clinical potential. Perhaps the most striking development is the use of PET in oncology. PET imaging is approved in the United States for lung, lymphoma, colon, and melanoma cancer imaging. Data are accumulating rapidly to attest the efficacy of Fluorine-18 fluorodeoxyglucose (FDG) imaging in a wide variety of malignant tumors with sensitivities and specificities often in the high 90s. FDG uptake has been shown in tumors of the head and neck, ovary, breast, musculoskeletal system, and neuroendocrine system as well. The major role of PET has emerged as a reliable method for evaluating and staging recurrent disease. But it also has an important role in differentiating benign and malignant primary tumors. This has been shown particularly well in the differential diagnosis of solitary lung nodules. Although FDG has emerged as the dominant radiopharmaceutical for PET imaging in oncology, numerous other compounds are being evaluated. It is likely that more specific and efficacious compounds will be introduced during the next decade. F-18, because of its highly favorable physical characteristics, is likely to become the technetium of PET imaging. The next decade will witness an explosive growth of PET technology in oncologic imaging.

Tumor marker determination after orthotopic heart transplantation

BACKGROUND

Because the risk of developing malignant tumors after heart transplantation is approximately 100-fold higher, methods for rapid diagnosis must be developed to allow early and aggressive treatment in these patients. Although tumor markers have been used frequently for surveying already detected cancer, we studied their value in screening for tumors in heart transplant patients.

METHODS

The levels of the tumor markers CEA, CA19-9, CA125, CA72-4, TPA, TPS, and CYFRA 21-1 were determined prospectively in 3-month intervals in 91 heart transplant patients between 1993 and 1998.

RESULTS

In eight patients a definite diagnosis of cancer was made during the marker survey (mean observation time 2.85 +/- 1.3 years), including bronchogenic carcinoma in six, renal carcinoma in one, and colon cancer in one. All patients with bronchogenic carcinoma were smokers. The markers had a sensitivity below 60% to detect cancer. Given a 2-fold cutoff level (10 ng/mL), the CEA was the only marker with sufficient specificity (93.8%, only one false-positive result). Two patients were symptom-free even though they had elevated CEA levels. In one of those patients, disseminated intractable cancer was diagnosed at first evaluation, whereas no tumor was found in the other case at first evaluation. Subsequently, by means of fluorodeoxyglucose positron emission tomography, a hypermetabolic region was found in the right upper mediastinum. Control computed tomographic scan 4 weeks after the first investigation showed disseminated intractable disease also in this patient. Another heart transplant patient with colon cancer showed a normalization of the CEA after hemicolectomy and an increase in the CEA when liver dissemination developed. There was a relationship between cardiac death and CA125 and TPS in some heart transplant patients.

CONCLUSIONS

We conclude that the CEA is the only tumor marker with adequate sensitivity and specificity to detect subclinical malignancies in the follow-up of heart transplant patients. However, because of several limitations (limited diagnostic and therapeutic possibilities and enormous costs), we cannot recommend screening by tumor markers on a regular basis. Because of the elevated risk of cancer in patients who had organ transplantation, further prophylactic measures, especially smoking cessation programs, must be developed. Once a malignancy is diagnosed, tumor markers can help target clinical decisions. Additionally, nonspecific increases in CA125 and TPS levels might be related to nonmalignant circulatory disturbances and cardiac death.

Nuclear medicine in cancer diagnosis

Nuclear medicine imaging has contributed significantly to diagnosis, treatment planning, and the evaluation of response to treatment in patients with cancer since the development of modern techniques in the 1970s. Diagnostic applications such as the bone scan continue to be the most common use in oncology because of their high sensitivity but the contribution of nuclear medicine to oncology can perhaps be best understood in the context of patient management. Staging of newly presenting cancer patients and restaging for treatment planning are reviewed here. For treatment response and disease recurrence nuclear medicine provides information non-invasively. The studies can be repeated with few side-effects and with low radiation absorbed doses. Results can be directly correlated with clinical laboratory data. The goals of biologically characterising an individual patient's tumour and predicting his or her response to treatment are within reach.

Potential use of FDG-PET scan after induction chemotherapy in surgically staged IIIa-N2 non-small-cell lung cancer: a prospective pilot study. The Leuven Lung Cancer Group

BACKGROUND

Clearance of viable tumour cells in mediastinal lymph nodes (MLN) by induction chemotherapy (IC)--so-called MLN downstaging--is an important aspect of combined-modality treatment of N2-NSCLC. Reassessment of MLN after IC by CT is far from accurate, while re-mediastinoscopy is often technically difficult. Based on our previous results with FDG-PET in the initial staging of N2 disease, we investigated whether PET after IC could be helpful in predicting MLN downstaging and therapeutic outcome.

PATIENTS AND METHODS

Patients underwent a first PET before IC. After three cycles of platinum-based IC, a second PET was performed before locoregional therapy, either surgery or radiotherapy. PET results were correlated with pathology of the MLN when available, and with survival.

RESULTS

Fifteen surgically staged N2-NSCLC patients were prospectively included. Locoregional therapy after IC consisted of surgery in nine and radiotherapy in six. Correlation with pathology of the nine resection specimens revealed that the accuracy of PET in predicting MLN downstaging was 100% (six true negatives; three true positives), whereas for CT it was only 67% (two false pos; one false neg). Reassessment with PET after IC was correlated with the outcome after the entire combined modality treatment. Survival was significantly better in patients with mediastinal clearance (P = 0.01) or with a greater than 50% decrease in the Standardised Uptake Value (SUV) of the primary tumour (P = 0.03) after IC.

CONCLUSIONS

Mediastinal PET after IC accurately assesses pathologic MLN downstaging in N2-NSCLC. The data suggest a possible correlation of early survival with mediastinal clearance and an important decrease of SUV in the primary tumour. Confirmation of these preliminary findings would establish PET as a useful non-invasive tool to select patients for intensive locoregional treatment after IC.

Applications of PET in lung cancer

An estimated 180,000 new cases of lung cancer will be diagnosed in the United States this year, and lung cancer accounts for approximately 25% of all cancer deaths. The overall 5-year survival rate is 14%, and this has not changed over the past several decades. Lung cancer diagnosis and treatment is a major health problem globally. Most lung cancers are detected initially on chest radiographs, but many benign lesions have radiologic characteristics similar to malignant lesions. Thus, additional studies are required for further evaluation. Computed tomography (CT) is most frequently used to provide additional anatomic and morphologic information about the lesion, but it is limited in distinguishing benign from malignant abnormalities in the lung, pleura, and mediastinum. Because of the indeterminate results from anatomic imaging, biopsy procedures including thoracoscopy and thoracotomy may be used even through one-half of the lesions removed are benign and do not need to be removed. FDG-PET imaging provides physiologic and metabolic information that characterizes lesions that are indeterminate by CT and that accurately stages the distribution of lung cancer. Exploiting the fundamental biochemical differences between cancer and normal tissues, FDG imaging takes advantage of the increased accumulation of FDG in transformed cells. FDG-PET is very sensitive (approximately 95%) for the detection of cancer in patients who have indeterminate lesions on CT. The specificity (approximately 85%) of PET imaging is slightly less than the sensitivity because some inflammatory processes such as active granulomatous infections accumulate FDG avidly. The high-negative predictive value of PET suggests that lesions considered negative on the study are benign, biopsy is not needed, and radiographic follow-up is recommended. Several studies have documented the increased accuracy of PET compared with CT in the evaluation of the hilar and mediastinal lymph node status in patients with lung cancer. If the mediastinum is normal on PET imaging and there is no other evidence of metastatic disease, the patient has a thoracotomy. If the mediastinum is abnormal on PET imaging, mediastinoscopy is performed with the PET images providing the lymph node stations to target. Whole-body PET studies detect metastatic disease that is unsuspected by conventional imaging and demonstrate some of the anatomic abnormalities detected by CT to be benign lesions. Management changes have been reported to occur in up to 41% of patients based on the results of the whole-body studies.