Measurement of clinical and subclinical tumour response using [18F]-fluorodeoxyglucose and positron emission tomography: review and 1999 EORTC recommendations. European Organization for Research and Treatment of Cancer (EORTC) PET Study Group

Standardised uptake values from PET/CT images: comparison with conventional attenuation-corrected PET

PURPOSE

In PET/CT, CT-derived attenuation factors may influence standardised uptake values (SUVs) in tumour lesions and organs when compared with stand-alone PET. Therefore, we compared PET/CT-derived SUVs intra-individually in various organs and tumour lesions with stand-alone PET-derived SUVs.

METHODS

Thirty-five patients with known or suspected cancer were prospectively included. Sixteen patients underwent FDG PET using an ECAT HR+scanner, and subsequently a second scan using a Biograph Sensation 16PET/CT scanner. Nineteen patients were scanned in the reverse order. All images were reconstructed with an iterative algorithm (OSEM). Suspected lesions were grouped as paradiaphragmatic versus distant from the diaphragm. Mean and maximum SUVs were also calculated for brain, lung, liver, spleen and vertebral bone. The attenuation coefficients (mu values) used for correction of emission data (bone, soft tissue, lung) in the two data sets were determined. A body phantom containing six hot spheres and one cold cylinder was measured using the same protocol as in patients.

RESULTS

Forty-six lesions were identified. There was a significant correlation of maximum and mean SUVs derived from PET and PET/CT for 14 paradiaphragmatic lesions (r=0.97 respectively; p<0.001 respectively) and for 32 lesions located distant from the diaphragm (r=0.87 and r=0.89 respectively; p<0.001 respectively). No significant differences were observed in the SUVs calculated with PET and PET/CT in the lesions or in the organs. In the phantom, radioactivity concentration in spheres calculated from PET and from PET/CT correlated significantly (r=0.99; p<0.001).

CONCLUSION

SUVs of cancer lesions and normal organs were comparable between PET and PET/CT, supporting the usefulness of PET/CT-derived SUVs for quantification of tumour metabolism.

L’examen TEP au fluorodésoxyglucose-(18F) et son impact sur la décision thérapeutique en cancérologie

FDG, a radioactive glucose analog for PET imaging, requires some precautions: it should be used only in patients with glycemia < 7mmol/L, fasting for at least 6 h but well hydrated, and after pregnancy is ruled out. FDG-PET has many indications in oncology. Its clinical utility has been documented in some circumstances, listed as routine indications in the European Principal Characteristics Summary and the French Standards, Options, and Recommendations. The European "Points to Consider" define as a principal criterion of clinical utility the impact of the imaging results on patient management. The original results presented here evaluate the clinical impact of FDG-PET among patients at Tenon Hospital by the rate of modifications in patient' management, determined with the same questionnaire as that used in two California studies of 2044 patients. Our response rate was lower than in our previous retrospective study in 2000 (34% versus 73%), probably because a prospective evaluation requires more work by the referring physician (who had to respond to two separate letters). On the other hand, the modification rate rose significantly (54% versus 46%, p<0.001), especially for colorectal cancer (58% versus 44%, p<0.02). The California studies had similar response rates (31%-48%, depending on the indication). Their modification rates were also similar, although higher for lymphoma (68%), colorectal (65%) and breast (58%) cancers.

La TEP dans les cancers des voies aérodigestives supérieures

FDG PET is useful when cancer in the head or neck (except for tumors of the salivary glands, which cannot be characterized accurately) is diagnosed or suspected but not confirmed by biopsy. It can, for example, find evidence of suspicious lymph nodes in clinically N0 necks, detect foci suggestive of distant metastases or second cancers, and provide useful prognostic information. Because it can be very difficult to identify anatomical structures and landmarks on PET images in the head and neck region, PET/CT fusion is very helpful in this area. In early assessment of chemotherapy, the absence of a significant reduction in FDG uptake after one or two cycles predicts lack of efficacy and thus indicates the need to modify the regimen. Conversely, the disappearance of FDG foci indicates effective treatment and good prognosis but cannot rule out the persistence of any malignant tissue at the end of treatment, especially neoadjuvant. Diagnostic impact is probably greatest in monitoring for recurrence and restaging known recurrence: FDG PET should be performed - perhaps routinely - early enough that curative options are still open, but long enough after the end of treatment to avoid false positive results from inflammation. The strategy and timing of FDG PET during follow-up should be determined in more detail in the future, as should the role (if any) of fluorotyrosine (FET) PET in squamous cell carcinoma.

[Image reconstruction and quantification in emission tomography]

Radionuclide tomographic imaging has substantially benefited from the introduction of statistical image reconstruction. Although the main concepts of these iterative algorithms were published decades ago, their widespread use in clinical routine only became available with faster computers for image processing in the last few years. This article gives an overview of data acquisition and iterative reconstruction in emission tomography, deals with the popular maximum likelihood algorithm, and describes the basics of the maximum a posteriori reconstruction. Prerequisites and corrections necessary for quantification are discussed in the second part of the article on the basis of positron emission tomography. Improvements in technical equipment are expected to stimulate future research into image reconstruction.

Interobserver and Intraobserver Variability of Standardized Uptake Value Measurements in Non–small-cell Lung Cancer

OBJECTIVES

To assess interobserver and intraobserver variabilities in measuring the maximal standardized uptake value (SUV) of non-small-cell lung cancer.

METHODS

Positron emission tomography-computed tomography examinations of 20 consecutive patients referred for initial evaluation of newly diagnosed non-small-cell lung cancer were retrospectively reviewed by 5 experienced positron emission tomography-computed tomography readers, who independently measured the maximal SUV/body weight of the primary tumors. Interobserver and intraobserver variabilities were assessed by using 4 statistical methods: correlation, regression analysis, Bland-Altman analysis, and analysis of variance. The SUV measurements derived in the study were compared with the SUV measurements documented in the original reports using correlation and regression analysis. The percentages of tumors whose retrospective SUV measurements were more than 20% different and more than 25% different from those in the original report were assessed.

RESULTS

Both interobserver and intraobserver SUV measurements were highly reproducible. Pearson correlation coefficients were greater than 0.95 and 0.94, respectively. Good interobserver and intraobserver agreement was shown with regression analysis (F test P value >0.05), the Bland-Altman analysis, and analysis of variance (F test P value >0.95). The mean original SUV was much less than the mean study SUV (P<0.05). The study SUV differed from the SUV of the original report by more than 20% in 50% of the tumors, and by more than 25% in 45% of the tumors.

CONCLUSIONS

There was excellent interobserver and intraobserver agreement in SUVs measured in the study environment but poor agreement between study SUVs and those documented in original reports, which can affect treatment decisions substantially.

Positron emission tomography as an imaging biomarker

Positron emission tomography (PET) allows noninvasive, quantitative studies of various biologic processes in the tumor tissue. By using PET, investigators can study the pharmacokinetics of anticancer drugs, identify various therapeutic targets and monitor the inhibition of these targets during therapy. Furthermore, PET provides various markers to assess tumor response early in the course of therapy. A significant number of studies have now shown that changes in tumor glucose utilization during the first weeks of chemotherapy are significantly correlated with patient outcome. These data suggest that PET may be used as a sensitive test to assess the activity of new cytotoxic agents in phase II studies. Furthermore, early identification of nonresponding tumors provides the opportunity to adjust treatment regimens according to the individual chemosensitivity of the tumor tissue. However, further prospective and randomized validation of PET is still required before PET controlled chemotherapy can be used in clinical practice.

Early change in glucose metabolic rate measured using FDG-PET in patients with high-grade glioma predicts response to temozolomide but not temozolomide plus radiotherapy

PURPOSE

To compare the ability of positron emission tomography (PET) to predict response to temozolomide vs. temozolomide plus radiotherapy.

METHODS AND MATERIALS

Nineteen patients with high-grade glioma (HGG) were studied. Patients with recurrent glioma received temozolomide 75 mg/m2 daily for 7 weeks (n=8). Newly diagnosed patients received temozolomide 75 mg/m2 daily plus radiotherapy 60 Gy/30 fractions over 6 weeks, followed by six cycles of adjuvant temozolomide 200 mg/m2/day (Days 1-5 q28) starting 1 month after radiotherapy (n=11). [18F]Fluorodeoxyglucose ([18F]FDG) PET scan and magnetic resonance imaging (MRI) were performed at baseline, and 7 and 19 weeks after initiation of temozolomide administration. Changes in glucose metabolic rate (MRGlu) and MRI response were correlated with patient survival.

RESULTS

In the temozolomide-alone group, patients who survived>26 vs. <or=26 weeks showed a greater reduction in MRGlu measured at 7 weeks with median changes of -34% and -4%, respectively (p=0.02). PET responders, defined as a reduction in MRGlu>or=25%, survived longer than nonresponders with mean survival times of 75 weeks (95% CI, 34-115 vs. 20 weeks (95% CI, 14-26) (p=0.0067). In the small group of patients studied, there was no relationship between MRI response and survival (p=0.52). For patients receiving temozolomide plus radiotherapy, there was no difference in survival between PET responders and nonresponders (p=0.32).

CONCLUSIONS

Early changes in MRGlu predict response to temozolomide, but not temozolomide plus radiotherapy.

Minimally invasive pharmacokinetic and pharmacodynamic technologies in hypothesis-testing clinical trials of innovative therapies

Clinical trials of new cancer drugs should ideally include measurements of parameters such as molecular target expression, pharmacokinetic (PK) behavior, and pharmacodynamic (PD) endpoints that can be linked to measures of clinical effect. Appropriate PK/PD biomarkers facilitate proof-of-concept demonstrations for target modulation; enhance the rational selection of an optimal drug dose and schedule; aid decision-making, such as whether to continue or close a drug development project; and may explain or predict clinical outcomes. In addition, measurement of PK/PD biomarkers can minimize uncertainty associated with predicting drug safety and efficacy, reduce the high levels of drug attrition during development, accelerate drug approval, and decrease the overall costs of drug development. However, there are many challenges in the development and implementation of biomarkers that probably explain their disappointingly low implementation in phase I trials. The Pharmacodynamic/Pharmacokinetic Technologies Advisory committee of Cancer Research UK has found that submissions for phase I trials of new cancer drugs in the United Kingdom often lack detailed information about PK and/or PD endpoints, which leads to suboptimal information being obtained in those trials or to delays in starting the trials while PK/PD methods are developed and validated. Minimally invasive PK/PD technologies have logistic and ethical advantages over more invasive technologies. Here we review these technologies, emphasizing magnetic resonance spectroscopy and positron emission tomography, which provide detailed functional and metabolic information. Assays that measure effects of drugs on important biologic pathways and processes are likely to be more cost-effective than those that measure specific molecular targets. Development, validation, and implementation of minimally invasive PK/PD methods are encouraged.

Monitoring chemotherapy and radiotherapy of solid tumors

PET imaging with the glucose analog fluorodeoxyglucose (FDG-PET) has been evaluated in numerous studies to monitor tumor response in patients undergoing chemo- and radiotherapy. The clinical value of FDG-PET for differentiation of residual or recurrent viable tumor and therapy-induced fibrosis or scar tissue has been documented for various solid tumors. Furthermore, there are now several reports suggesting that quantitative assessment of therapy-induced changes in tumor FDG uptake may allow prediction of tumor response and patient outcome very early in the course of therapy. In nonresponding patients, treatment may be adjusted according to the individual chemo- and radiosensitivity of the tumor tissue. Since the number of alternative treatments for solid tumors (e.g., second-line chemotherapy agents, protein kinase, or angiogenesis inhibitors) is continuously increasing, early prediction of tumor response to chemotherapy and radiotherapy by FDG-PET has enormous potential to "personalize" treatment and to reduce the side-effects and costs of ineffective therapy.

Imaging vascular physiology to monitor cancer treatment

The primary physiological function of the vasculature is to support perfusion, the nutritive flow of blood through the tissues. Vascular physiology can be studied non-invasively in human subjects using imaging methods such as positron emission tomography (PET), magnetic resonance imaging (MRI), X-ray computed tomography (CT), and Doppler ultrasound (DU). We describe the physiological rationale for imaging vascular physiology with these methods. We review the published data on repeatability. We review the literature on 'before-and-after' studies using these methods to monitor response to treatment in human subjects, in five broad clinical settings: (1) antiangiogenic agents, (2) vascular disruptive agents, (3) conventional cytotoxic drugs, (4) radiation treatment, and (5) agents affecting drug delivery. We argue that imaging of vascular physiology offers an attractive 'functional endpoint' for clinical trials of anticancer treatment. More conventional measures of tumour response, such as size criteria and the uptake of fluorodeoxyglucose, may be insensitive to therapeutically important changes in vascular function.

Utilidad de la PET con FDG en el estudio de estadificación inicial, recurrencia y respuesta al tratamiento con imatinib (Glivec) en pacientes diagnosticados de un tumor del estroma gastrointestinal

INTRODUCTION

Gastrointestinal stromal tumors (GISTs) account for almost 4 % of all gastrointestinal neoplasms. Recently, a new type of tyrosine kinase inhibitor (Glivec), has been successfully used in patients with metastasic or unresectable disease. The aim of the study is to show the utility of PET in the staging, recurrence and treatment response to Glivec in GIST tumors.

MATERIALS AND METHODS

48 whole body FDG-PET studies in 27 patients with GIST (19 men/mean age = 56 y) were evaluated for initial staging (n = 13), recurrence (n = 15) or treatment response to Glivec (n = 20). Images were acquired in a whole body 2D mode using attenuation correction on an Advance Nxi G.E.MS camera and were evaluated visually and quantatively using SUV analysis. Results were compared with radiological findings, hystological confirmation or follow-up.

RESULTS

In the initial staging evaluation, FDG-PET shows a more extensive disease than suspected in 3/10 patients. In other 3 patients PET ruled out mesenteric or peritoneal disease. In the evaluation of treatment response to Glivec, FDG-PET showed a good response in eleven patients (complete response in seven and partial response in four). In this group a sixty percent decrease of the SUV max was assessed. Two patients showed no response to Glivec at doses of 400 mg or 800 mg, showing a stable SUV value and/or increased in some abdominal lesions. PET detected recurrence in one patient.

CONCLUSIONS

This study show how FDG-PET is accurate in the early treatment response to Glivec. PET could be helpful in the staging and recurrence of GIST tumors.

Impact of FDG PET for staging of Ewing sarcomas and primitive neuroectodermal tumours

AIM

High-grade Ewing sarcomas and Primitive neuroectodermal tumours (PNET) make up the tumours of the Ewing family. Our purpose was to evaluate the value of [18F]fluorodeoxyglucose positron emission tomography (FDG PET) in patients with Ewing tumours.

PATIENTS AND METHODS

Twenty-four patients who had PET because of a suspected Ewing tumour during a 5-year period were included in this retrospective study. The images of 33 whole-body FDG PET investigations performed in primary or secondary diagnostics were analysed visually and semi-quantitatively by using standardized uptake values (SUVs). In 14 cases, PET was compared to bone scintigraphy regarding bone lesions. The final diagnosis was based on histology, imaging and follow-up.

RESULTS

Histologically, the primary lesions were 10 Ewing sarcoma, 13 PNET and one osteomyelitis. The sensitivity and specificity of an examination-based analysis (presence of Ewing tumour and/or its metastases) were 96 and 78%, respectively. Altogether, 163 focal lesions were evaluated. Sensitivity and specificity regarding individual lesions were 73 and 78%. This lower sensitivity is mainly due to small lesions. In true-positive cases, the mean SUV was 4.54+/-2.79, and the SUVs in two false-positive cases were 4.66 and 1.60. True-positive and false-positive cases could not be differentiated definitively based on SUVs because of overlap and low values in true-positive lesions. In four cases, PET depicted 70 while bone scintigraphy depicted only eight bone metastases.

CONCLUSION

An FDG PET investigation is a valuable method in the case of Ewing tumours. PET is superior to bone scintigraphy in the detection of bone metastases of Ewing tumours. For the depiction of small lesions, mainly represented by pulmonary metastases, PET is less sensitive than helical computed tomography. Determination of the role of whole-body FDG PET in diagnostic algorithm needs further investigation.

[18F]Fluorodeoxyglucose positron emission tomography predicts outcome for Ewing sarcoma family of tumors

PURPOSE

Response to neoadjuvant chemotherapy is a significant prognostic factor for the Ewing sarcoma family of tumors (ESFTs). [18F]fluorodeoxyglucose (FDG) positron emission tomography (PET) is a noninvasive imaging modality that accurately predicts histopathologic response in several malignancies. To determine the prognostic value of FDG PET response for progression-free survival (PFS) in ESFTs, we reviewed the University of Washington Medical Center experience.

PATIENTS AND METHODS

Thirty-six patients with ESFTs were evaluated by FDG PET. All patients received neoadjuvant and adjuvant chemotherapy. FDG PET standard uptake values before (SUV1) and after (SUV2) chemotherapy were analyzed and correlated with chemotherapy response, as assessed by histopathology in surgically excised tumors. Thirty-four patients had both SUV1 and SUV2.

RESULTS

The mean SUV1, SUV2, and ratio of SUV2 to SUV1 (SUV2:1) were 7.9 (range, 2.3 to 32.8), 2.1 (range, 0 to 4.3), and 0.36 (range, 0.00 to 1.00), respectively. Good FDG PET response was defined as SUV2 less than 2.5 or SUV2:1 < or = 0.5. FDG PET response by SUV2 or SUV2:1 was concordant with histologic response in 68% and 69% of patients, respectively. SUV2 was associated with outcome (4-year PFS 72% for SUV2 < 2.5 v 27% for SUV2 > or = 2.5, P = .01 for all patients; 80% for SUV2 < 2.5 v 33% for SUV2 > or = 2.5, P = .036 for localized at diagnosis patients). SUV2:1 < or = 0.5 was not predictive of PFS.

CONCLUSION

FDG PET imaging of ESFTs correlates with histologic response to neoadjuvant chemotherapy. SUV2 less than 2.5 is predictive of PFS independent of initial disease stage.

Quantifying the Effect of IV Contrast Media on Integrated PET/CT: Clinical Evaluation

OBJECTIVES

The use of IV contrast media in PET/CT can result in an overestimation of PET attenuation factors that potentially can affect interpretation. The objective of this study was to quantify the effect of IV contrast media in PET/CT and assess its impact on patients with intrathoracic malignancies.

MATERIALS AND METHODS

Nine patients had CTs performed with and without IV contrast media followed by (18)F-FDG PET. PET images were reconstructed using contrast-enhanced and unenhanced CT. To quantify the effect of contrast media on standardized uptake values (SUV), similar regions of interest (ROIs) were drawn on the subclavian vein, heart, liver, spleen, and site of malignancy on both CT and corresponding reconstructed PET images, and the mean and maximum values were compared. In addition, two physicians blinded to the imaging parameters that were used evaluated the reconstructed PET images to assess whether IV contrast media had an effect on clinical interpretation.

RESULTS

For all patient studies, the subclavian vein region on the ipsilateral side of contrast media administration had the highest increase in CT numbers with a corresponding average SUV(max) increase of 27.1%. Similarly, ROIs of the heart and at the site of malignancy showed an increase in the maximum attenuation value with a corresponding average SUV(max) increase of 16.7% and 8.4%, respectively. Other locations had relatively small attenuation value differences with a correspondingly negligible SUV variation.

CONCLUSION

Although there is a significant increase in SUV in regions of high-contrast concentration when contrast-enhanced CT is used for attenuation correction, this increase is clinically insignificant. Accordingly, in PET/CT, IV contrast-enhanced CT can be used in combination with the PET to evaluate patients with cancer.

Response monitoring of neoadjuvant therapy using CT, EUS, and FDG-PET

Neoadjuvant or adjuvant multimodality therapy in oesophageal cancer is introduced in an effort to improve prognosis. However, in a substantial fraction of patients there is no response to this non-surgical therapy. Non-invasive imaging modalities such as computed tomography (CT), endoscopic ultrasound (EUS) and 18F-2-fluoro-2-deoxy-d-glucose positron emission tomography (FDG-PET) have been evaluated for assessing patient response to therapy, and these are described in this review. Currently, FDG-PET seems to be the best available tool for neoadjuvant therapy response assessment in oesophageal cancer.

Molecular imaging: what can be used today

Biochemical cellular targets and more general metabolic processes in cancer cells can be visualised. Extensive data are available on molecular imaging in preclinical models. However, innovative tracers move slowly to the clinic. This review provides information on the currently available methods of metabolic imaging, especially using PET in humans. The uptake mechanisms of tracer methods and a brief discussion of the more ‘molecular’ targeted methods are presented. The main focus is on the different classes of tracers and their application in various types of cancer within each class of tracers, based on the current literature and our own experience. Studies with [¹⁸F]FDG (energy metabolism), radiolabelled amino acids (protein metabolism), [¹⁸F]FLT (DNA metabolism), [¹¹C]choline (cell membrane metabolism) as general metabolic tracer methods and [¹⁸F]DOPA (biogenic amine metabolism) as a more specific tracer method are discussed. As an example, molecular imaging methods that target the HER2 receptor and somatostatin receptor are described.

Esophageal cancer: CT, endoscopic US, and FDG PET for assessment of response to neoadjuvant therapy--systematic review

PURPOSE

To compare diagnostic accuracy of computed tomography (CT), endoscopic ultrasonography (US), and fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET) for assessment of response to neoadjuvant therapy in patients with esophageal cancer by using a systematic review of the literature.

MATERIALS AND METHODS

MEDLINE and EMBASE databases and Cochrane Database of Systematic Reviews were searched for relevant studies. Two reviewers independently assessed the methodological quality of each study. Summary receiver operating characteristic (ROC) analysis was used to summarize and compare the diagnostic accuracy of the three modalities.

RESULTS

Four studies with CT, 13 with endoscopic US, and seven with FDG PET met inclusion criteria. Percentages of the maximum score in regard to methodological quality ranged from 15% to 100%. Summary ROC analysis could be performed for three studies with CT, four with endoscopic US, and four with FDG PET. The maximum joint values for sensitivity and specificity were 54% for CT, 86% for endoscopic US, and 85% for FDG PET. Accuracy of CT was significantly lower than that of FDG PET (P < .006) and of endoscopic US (P < .003). Accuracy of FDG PET and that of endoscopic US were similar (P = .839). In all patients, CT was always feasible, whereas endoscopic US was not feasible in 6% of the patients, and FDG PET was not feasible in less than 1%.

CONCLUSION

CT has poor accuracy for assessment of response to neoadjuvant therapy in patients with esophageal cancer. Endoscopic US and FDG PET have equivalent good accuracy, but endoscopic US is not always feasible after chemotherapy and radiation therapy. FDG PET seems to be a promising noninvasive tool for assessment of neoadjuvant therapy in patients with esophageal cancer.

Blood flow–metabolic relationships are dependent on tumour size in non-small cell lung cancer: a study using quantitative contrast-enhanced computer tomography and positron emission tomography

PURPOSE

The purpose of this study was to undertake dual assessment of tumour blood flow and glucose metabolism in non-small cell lung cancer (NSCLC) using contrast-enhanced computed tomography (CE-CT) and (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET) in order to assess how the relationships between these parameters vary with tumour size and stage.

METHODS

Tumour blood flow and glucose metabolism were assessed in 18 NSCLCs using quantitative CE-CT and FDG-PET respectively. Contrast enhancement and FDG uptake were both normalised to injected dose and patient weight to yield correspondingly the standardised perfusion value (SPV) and standardised uptake value (SUV). Tumour area was measured from conventional CT images.

RESULTS

The ratio of SUV to SVP and the metabolic-flow difference (SUV-SVP) correlated with tumour size (r=0.56, p=0.015 and r=0.60 and p=0.008 respectively). A metabolic-flow difference of greater than 4 was more common amongst tumours of stages III and IV (odds ratio 10.5; 95% confidence limits 0.24-32.1). A significant correlation between SUV and SPV was found only for tumours smaller than 4.5 cm2 (r=0.85, p=0.03).

CONCLUSION

Blood flow-metabolic relationships are not consistent in NSCLC but depend upon tumour size and stage. Quantitative CE-CT as an adjunct to an FDG study undertaken using integrated PET-CT offers an efficient way to augment the assessment of tumour biology with possible future application as part of clinical care.

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.

Critical issues in response evaluation on computed tomography: lessons from the gastrointestinal stromal tumor model

Imaging technology plays a major role in treatment response assessment in solid tumors and in surveillance for recurrence or progression. Currently available response evaluation criteria, Response Evaluation Criteria in Solid Tumors (RECIST), are based on unidimensional tumor size. Recently, however, these strictly size-based criteria for evaluating responses have been criticized because they do not reflect the biologic changes of solid tumors induced by targeted therapies and thus may be misleading. This problem is evident in response evaluation in advanced gastrointestinal stromal tumor (GIST) treated with a new molecularly targeted agent, imatinib. GISTs can increase in size despite good response to imatinib, and focal progression within a responding GIST can be overlooked with current size-based imaging criteria. Modified objective criteria using a combination of tumor size and density on CT are promising in early response evaluation and in predicting long-term prognosis in patients with advanced GIST treated with imatinib. These criteria may have broad applicability as additional targeted therapies become available to treat solid tumors.

Standardised FDG uptake: A prognostic factor for inoperable non-small cell lung cancer

The aim of this study was to investigate the relationship between standardised uptake value (SUV) obtained from [(18)F]fluorodeoxyglucose positron emission tomography (FDG PET) and treatment response/survival of inoperable non-small cell lung cancer (NSCLC) patients treated with high dose radiotherapy. Fifty-one patients were included recording stage, performance, weight loss, tumour volume, histology, lymph node involvement, SUV, and delivered radiation dose. The maximum SUV (SUV(max)) within the primary tumour was a sensitive and specific factor for predicting treatment response. Apart from SUV(max), stage and performance were also independent predictive factors for treatment response. In a multivariate disease-specific survival (DSS) analysis, SUV(max) (P = 0.01), performance status (P = 0.008) and stage (P = 0.04) were prognostic factors. For overall survival (OS), SUV(max) (P = 0.001) and performance (P = 0.06) were important prognostic factors. SUV(max) was an important prognostic factor for survival of inoperable NSCLC patients and a predictive factor for treatment response. Although the number of patients was small, the treatment was not homogeneous and the use of FDG SUV may have had constraints, we still conclude that the FDG SUV is potentially a good indicator for selecting patients for different treatment strategies.

Evaluation of Therapy for Lymphoma

Positron emission tomography (PET) using (18)F-fluorodeoxyglucose ((18)F-FDG) is the best noninvasive imaging technique for to assess response in patients suffering from lymphoma. Early response evaluation ("interim PET") after one, a few cycles, or at midtreatment can predict response, progression-free survival, and overall survival. We calculated from data of 7 studies an overall sensitivity to predict treatment failure of 79%, a specificity of 92%, a positive predictive value (PPV) of 90%, a negative predictive value (NPV) of 81%, and an accuracy of 85%. Although it is not yet indicated to change patient management based on residual (18)F-FDG uptake on interim scan in chemotherapy-sensitive patients, prospective studies evaluating the role of an interim PET in patient management clearly are warranted. (18)F-FDG PET also has an important prognostic role in relapsing patients after reinduction chemotherapy before high-dose chemotherapy (HCT) followed by autologous stem cell transplantation (ASCT). However, all chemotherapy-sensitive patients remain candidates for HCT followed by ASCT, even if (18)F-FDG PET showed residual (18)F-FDG uptake. We calculated from data of 3 studies an overestimated risk of relapse in 16% of all PET-positive patients. Some patients with residual (18)F-FDG uptake will have a good outcome after HCT followed by ASCT. (18)F-FDG PET is the imaging technique of choice for end-of-treatment evaluation. However, (18)F-FDG is not specific for tumoral tissue. Active inflammatory lesions and infectious processes can be falsely interpreted as malignant residual cells. However, a negative (18)F-FDG PET cannot exclude minimal residual disease. Consequently, it is always indicated to correlate PET findings with clinical data, other imaging modalities, and/or a biopsy. We calculated, from data of 17 studies in end-of-treatment evaluation, a sensitivity of 76%, a specificity of 94%, a PPV of 82%, a NPV 92%, and an accuracy of 89%.

The role of PET in monitoring therapy

Positron emission tomography (PET) is being increasingly used for the evaluation of patients with known or suspected cancer at all phases of the management process from diagnosis, through staging to follow-up after treatment. The role of PET in therapeutic monitoring is expanding rapidly due to its ability to provide earlier and more robust identification of non-responders than provided by conventional non-invasive imaging approaches. PET can thereby potentially provide important benefits to the individual patient by allowing an earlier change to alternative treatments that may be more efficacious or by avoiding the unnecessary toxicity related to ineffective therapy. As therapies become ever more expensive, this could also produce cost savings because of earlier termination of ineffective treatment. Conversely, PET may demonstrate important biological effects despite a lack of apparent morphological response and therefore prevent premature withdrawal of effective therapies. Globally, the vast majority of therapeutic monitoring studies use the glucose analogue, fluorine-18 fluorodeoxyglucose (FDG) but new tracers such as fluorine-18 fluorothymidine (FLT) also offer promise for this application. In this review, the potential benefits and limitations of FDG PET are discussed along with suggestions regarding the most practical methodologies for response evaluation using this modality.

Early restaging whole-body 18F-FDG PET during induction chemotherapy predicts clinical outcome in patients with locoregionally advanced nasopharyngeal carcinoma

PURPOSE

This study was undertaken to evaluate the utility of whole-body (18)F-FDG PET in monitoring therapeutic effect during induction chemotherapy (IC) and in predicting prognosis in patients with locoregionally advanced nasopharyngeal carcinoma (NPC).

METHODS

Fifty patients who had histologically proven, locoregionally advanced NPC without distant metastasis and had received IC were recruited in this study. The study cohort consisted of 19 females and 31 males (age 17-72 years, mean 45.9+/-11.9). Whole-body (18)F-FDG PET was performed in each patient after completion of one (33 patients) or two (17 patients) courses of IC. Each patient was restaged on the basis of the (18)F-FDG PET results. Patients who were downstaged to stage I or II were classified as major responders; the rest were classified as non-major responders.

RESULTS

Only 1 of the 23 major responders subsequently developed local recurrence. At the time of data analysis, all major responders were alive; by contrast, of the 27 non-major responders, 15 had locoregional recurrence or distant metastasis and nine had died (seven of NPC and two of treatment-related complications). Kaplan-Meier survival analysis showed significantly longer recurrence-free survival and overall survival in major responders (56.4+/-9.2 and 58.1+/-2.2 months) as compared with non-major responders (33.7+/-23.2 and 44.7+/-20.0 months), with p<0.0001 and p=0.0024, respectively.

CONCLUSION

The results of this study suggest that early restaging by a single whole-body (18)F-FDG PET scan after the first or second course of IC is useful for predicting therapeutic response and outcome in patients with locoregionally advanced NPC.

2-[11C]Thymidine Positron Emission Tomography Reproducibility in Humans

PURPOSE

To evaluate the reproducibility of 2-[11C]thymidine positron emission tomography (PET) scanning in patients with advanced intra-abdominal malignancies.

PATIENTS AND METHODS

The reproducibility of 2-[11C]thymidine PET was studied by comparing interpatient and intrapatient variability (coefficient of variability, COV) of both blood and tissue data. Arterial plasma metabolite levels were measured using on-line sampling and high-pressure liquid chromatography. 2-[11C]Thymidine retention in tissue was measured as the standardized uptake value at the end of the scan (SUV(end)), the area under the time-activity curve (AUC(0-1 hour)), and the fractional retention of thymidine (FRT). A group of seven patients were scanned 1 week apart with no intervening anticancer therapy.

RESULTS

There was interpatient variability in the levels of 2-[11C]thymidine and its main metabolite, 11CO2, in plasma. Variability in 2-[11C]thymidine PET data was greater between (COV: SUV(end) = 38%, AUC(0-1 hour) = 32%, FRT = 47%) than within (COV: SUV(end) = 8%, AUC(0-1 hour) = 2%, FRT = 9%) patients. There was a borderline significant difference between the paired tumor data for SUV(end) (P = 0.041), but not for AUC(0-1 hour) (P = 0.81) or FRT (P = 0.90). There was a good correlation between paired data for SUV(end) (r = 0.98), AUC(0-1 hour) (r = 0.99), and FRT (r = 0.95).

CONCLUSIONS

This is the first report showing that 2-[11C]thymidine PET scanning is reproducible in humans. Repeat scanning of tumor proliferation using 2-[11C]thymidine PET is feasible to perform in human intra-abdominal malignancies and should aid the future rapid assessment of antiproliferative tumor agents.

Molecular imaging of antiangiogenic agents

Many novel antiangiogenic agents are currently in various phases of clinical testing. These agents tend to be cytostatic, and therefore few responses are observed with conventional imaging by computerized tomography. Furthermore, toxicity with these agents is seen when the maximum-tolerated dose is combined with chemotherapy. Hence, there is a need to develop imaging strategies that can determine the minimum and optimum biologically active doses. There is increasing awareness of the need to obtain evidence of drug activity through the use of surrogate markers of the biologic mechanism of action during early clinical trials, in addition to determining the pharmacokinetics, toxicity profile, and maximum-tolerated dose. One of the major impediments to the rapid development of antiangiogenic agents in the past has been the lack of validated assays capable of measuring an antiangiogenic effect directly in patients. Recently, dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) has emerged as a useful technique for noninvasive imaging of tumor vasculature in preclinical and clinical models. The problem of tumor heterogeneity remains to be addressed. The major challenge is the standardization of the technique worldwide for the purpose of early clinical studies that are likely to be multicenter. Convincing data on correlations between changes observed through molecular imaging and changes in tumor angiogenesis, and hence tumor biology, are still lacking. Whether this would translate into a survival advantage remains to be seen. The ultimate test of the surrogate biological end points determined by molecular imaging will occur in randomized phase III trials. Results of the first randomized trial that showed a survival advantage in favor of antiangiogenic agents were released at the American Society of Clinical Oncology meeting in 2003. There it was reported that the combination of 5-fluorouracil, leucovorin, and irinotecan (Camptosar; Pfizer Pharmaceuticals; New York, NY) with anti-vascular endothelial growth factor antibody (bevacizumab-Avastin; Genentech, Inc.; South San Francisco, CA) was superior to the chemotherapy regimen alone when used to treat patients with metastatic colorectal cancer. However, until further phase III clinical trials confirm these results, surrogate end points of clinical efficacy of the newer agents are urgently needed so that development of ineffective drugs can be halted early. This review briefly discusses the role of molecular imaging in general, and DCE-MRI in particular, in relation to treatment with antiangiogenic agents and highlights some of the difficulties encountered in this area.

Increased fluorine-18 2-fluoro-2-deoxy-D-glucose (FDG) uptake in childhood CNS tumors is correlated with malignancy grade: a study with FDG positron emission tomography/magnetic resonance imaging coregistration and image fusion

PURPOSE Positron emission tomography (PET) has been used in grading of CNS tumors in adults, whereas studies of children have been limited. PATIENTS AND METHODS Nineteen boys and 19 girls (median age, 8 years) with primary CNS tumors were studied prospectively by fluorine-18 2-fluoro-2-deoxy-D-glucose (FDG) PET with (n = 16) or without (n = 22) H(2)(15)O-PET before therapy. Image processing included coregistration to magnetic resonance imaging (MRI) in all patients. The FDG uptake in tumors was semiquantitatively calculated by a region-of-interest-based tumor hotspot/brain index. Eight tumors without histologic confirmation were classified as WHO grade 1 based on location, MRI, and clinical course (22 to 42 months). Results Four grade 4 tumors had a mean index of 4.27 +/- 0.5, four grade 3 tumors had a mean index of 2.47 +/- 1.07, 10 grade 2 tumors had a mean index of 1.34 +/- 0.73, and eight of 12 grade 1 tumors had a mean index of -0.31 +/- 0.59. Eight patients with no histologic confirmation had a mean index of 1.04. For these 34 tumors, FDG uptake was positively correlated with malignancy grading (n = 34; r = 0.72; P < .01), as for the 26 histologically classified tumors (n = 26; r = 0.89; P < .01). The choroid plexus papilloma (n = 1) and the pilocytic astrocytomas (n = 3) had a mean index of 3.26 (n = 38; r = 0.57; P < .01). H(2)(15)O-uptake showed no correlation with malignancy. Digitally performed PET/MRI coregistration increased information on tumor characterization in 90% of cases. CONCLUSION FDG PET of the brain with MRI coregistration can be used to obtain a more specific diagnosis with respect to malignancy grading. Improved PET/MRI imaging of the benign hypermetabolic tumors is needed to optimize clinical use.

Imaging and Response in Soft Tissue Sarcomas

Conventional CT and MRI scans provide exquisite anatomic detail of soft tissue sarcomas but fall short of estimating the degree of tumor viability within a sarcomatous mass. Functional imaging methods that measure biologic properties within sarcomas may be better able to determine true tumor responses to chemotherapy or radiotherapy. Many different approaches to measure biologic processes have been taken and are discussed, but positron emission tomography (PET) is currently the most quantitative and developed. A response in tumor glucose uptake, determined by PET, has been shown to correlate with improved clinical outcomes in high-grade extremity soft tissue sarcomas and gastrointestinal stromal tumors. Functional imaging of soft tissue sarcomas may prove to be useful clinically, therefore further investigation is warranted.

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.

Comparison of CT, MRI and FDG-PET in response prediction of patients with locally advanced rectal cancer after multimodal preoperative therapy: is there a benefit in using functional imaging?

The aim of this study was to compare CT, MRI and FDG-PET in the prediction of outcome of neoadjuvant radiochemotherapy in patients with locally advanced primary rectal cancer. A total of 23 patients with T3/4 rectal cancer underwent a preoperative radiochemotherapy combined with regional hyperthermia. Staging was performed using four-slice CT (n=23), 1.5-T MRI (n=10), and (18)F-FDG-PET (n=23) before and 2-4 weeks after completion of neoadjuvant treatment. Response criteria were a change in T category and tumour volume for CT and MRI and a change in glucose uptake (standard uptake value) within the tumour for FDG-PET. Imaging results were compared with those of pretherapy endorectal ultrasound and histopathological findings. Histopathology showed a response to neoadjuvant therapy in 13 patients whereas 10 patients were classified as nonresponders. The mean SUV reduction in responders (60+/-14%) was significantly higher than in nonresponders (37+/-31%; P=0.030). The sensitivity and specificity of FDG-PET in identifying response was 100% (CT 54%, MRI 71%) and 60% (CT 80%, MRT 67%). Positive and negative predictive values were 77% (CT 78%, MRI 83%) and 100% (CT 57%, MRI 50%) (PET P=0.002, CT P=0.197, MRI P=0.500). These results suggest that FDG-PET is superior to CT and MRI in predicting response to preoperative multimodal treatment of locally advanced primary rectal cancer.

CT evaluation of the response of gastrointestinal stromal tumors after imatinib mesylate treatment: a quantitative analysis correlated with FDG PET findings

OBJECTIVE

We correlated changes in tumor density on CT with changes in glucose metabolism, or the maximum standardized uptake value (SUV(max)), on FDG PET and sought to develop CT imaging criteria that can be used to objectively evaluate tumor response in patients with metastatic gastrointestinal stromal tumors (GISTs) who undergo treatment with imatinib mesylate.

MATERIALS AND METHODS

Using the criteria established by the Response Evaluation Criteria in Solid Tumors (RECIST) group, we selected 173 tumors (in 36 patients) for study. Tumor size and density were determined objectively, and overall tumor response (OTR) was evaluated subjectively on CT images. The changes in these parameters before and after treatment were correlated with changes in SUV(max).

RESULTS

Significant decreases were seen in both tumor density (mean, 12.3 H [16.5%]; p < 0.0001) and SUV(max) (mean, 3.43 [64.9%]; p < 0.0001). OTR evaluated subjectively, correlated well with changes in SUV(max) (p < 0.0001). No statistically significant association was found between changes in tumor density and changes in SUV(max) (p = 0.3088), but 70% (14/20) of the patients with tumors that showed response on FDG PET exhibited at least a partial response by a change in tumor density. Tumor size was found to have decreased significantly 2 months after treatment (p = 0.0070). However, in 75% of the patients, the disease was stable according to the traditional tumor response criteria of RECIST.

CONCLUSION

FDG PET is sensitive and specific for evaluating tumor response but cannot be used in patients whose baseline FDG PET results are negative for tumors. Although subjective evaluation was a better indicator of treatment response than was tumor density alone, the tumor density measurement is a good indicator and provides a reliable quantitative means of monitoring the tumor. RECIST, using only tumor size, was unreliable for monitoring GISTs during the early stage of imatinib mesylate treatment.

Oxaliplatin combined with infusional 5-fluorouracil and concomitant radiotherapy in inoperable and metastatic rectal cancer: a phase I trial

The aim of this study was to define the recommended dose of oxaliplatin when combined with infusional 5-fluorouracil (5-FU) and concurrent pelvic radiotherapy. Eligible patients had inoperable rectal cancer, or symptomatic primary rectal cancer with metastasis. Oxaliplatin was given on day 1 of weeks 1, 3 and 5 of radiotherapy. Dose level 1 was oxaliplatin 70 mg m(-2) with 5-FU 200 mg m(-2) day(-1) continuous infusion 96 h week(-1). On dose level 2, the oxaliplatin dose was increased to 85 mg m(-2). On dose level 3, the duration of the 5-FU was increased to 168 h per week. Pelvic radiotherapy was 45 Gray (Gy) in 25 fractions over 5 weeks with a boost of 5.4 Gy. Fluorine-18 fluoro deoxyglucose and Fluorine-18 fluoro misonidazole positron emission tomography (FDG-PET and FMISO-PET) were used to assess metabolic tumour response and hypoxia. In all, 16 patients were accrued. Dose-limiting toxicities occurred in one patient at level 2 (grade 3 chest infection), and two patients at level 3 (grade 3 diarrhoea). Dose level 2 was declared the recommended dose level. FDG-PET imaging showed metabolic responses in 11 of the 12 primary tumours assessed. Four of six tumours had detectable hypoxia on FMISO-PET scans. The addition of oxaliplatin to infusional 5-FU chemoradiotherapy was feasible and generally well tolerated. For future trials, oxaliplatin 85 mg m(-2) and 5-FU 200 mg m(-2) day(-1) continuous infusion 96 h week(-1) is the recommended dose when combined with 50.4 Gy of pelvic radiotherapy.

The use of standardized uptake values for assessing FDG uptake with PET in oncology: a clinical perspective

Among clinicians who use positron emission tomography (PET), the standardized uptake value (SUV) is a popular semi-quantitative value that can be easily assessed whenever a PET study is performed under physiological and pathological conditions. It provides an index of regional tracer uptake normalized to the administered dose of tracer. The simplicity of SUV assessment contrasts with the complexity of full quantitative procedures requiring blood sampling and possibly dynamic scanning, which limits patient throughput and significantly increases the workload of a PET centre. Two main clinical conditions/variables affect the significance and usefulness of the SUV: the type and stage of the disease being assessed. Diagnosis, prognosis and therapy monitoring represent the possible uses of SUV. In the above clinical conditions an SUV may provide information about the single lesion in which it is assessed, but the utility of such information depends largely on its integration with all the available clinical and instrumental data.

Quantification in clinical fluorodeoxyglucose positron emission tomography

Positron emission tomography (PET) is increasingly used clinically to provide functional information on disease processes, especially in oncology using the glucose analogue 2-[18F]fluoro-2-deoxy-D-glucose (F-FDG). In the clinical setting it has become standard practice to use simplified imaging protocols compared to the often complex methods developed for research using PET. This is partly due to scarcity of resources but also for reasons of patient comfort and compliance, and not least expense and patient throughput. Fortunately the resulting loss in information can be justified to some extent on the grounds that in clinical PET it is usually relative rather than absolute metabolic rates that are of interest. Nonetheless, there remain unresolved questions of how best to perform quantification in clinical PET.

Prognostic significance of preoperative [18-F] fluorodeoxyglucose (FDG) positron emission tomography (PET) imaging in patients with resectable soft tissue sarcomas

OBJECTIVE

The objective of this study was to evaluate the prognostic significance of preoperative positron emission tomography (PET) using 2-fluoro-2-deoxy-D-glucose (FDG) by calculating the mean standardized uptake values (SUV) in patients with resectable soft tissue sarcomas (STS).

SUMMARY AND BACKGROUND DATA

FDG-PET might be used as an adjunctive tool (in addition to biopsy and radiologic tomography) in the preoperative prognostic assessment of resectable STS.

METHODS

A total of 74 adult patients with STS underwent preoperative FDG-PET imaging with calculation of the SUV. Clinicopathologic data and the SUV were analyzed for an association with the clinical outcome. The first and the third quartiles of the SUV distribution function were used as cutoff values (1.59 and 3.6). Survival was estimated by the Kaplan-Meier method. Univariate and multivariate analyses were performed using log-rank test and the Cox proportional hazards regression model.

RESULTS

In 55 cases, STS were completely resected (follow up 40 months): 5-year recurrence-free survival rates in patients with SUV <1.59, 1.59 to <3.6, and > or =3.6 were 66%, 24%, and 11%, respectively (P = 0.0034). SUV was a predictor for overall survival (5-year rates: 84% [SUV <1.59], 45% [SUV 1.59 to <3.6], and 38% [SUV > or =3.6]; P = 0.057) and local tumor control (5-year rates: 93% [SUV <1.59], 43% [SUV 1.59 to <3.6], and 15% [SUV > or =3.6]; P = 0.0017). By multivariate analysis, SUV was found to be predictive for recurrence-free survival. The prognostic differences with respect to the SUV were associated with tumor grade (P = 0.002).

CONCLUSION

The semiquantitative FDG uptake, as measured by the mean SUV on preoperative PET images in patients with resectable STS, is a useful prognostic parameter. SUV with cutoff values at the first and the third quartiles of the SUV distribution predicted overall survival, recurrence-free survival, and local tumor control. Therefore, FDG-PET can be used to improve the preoperative prognostic assessment in patients with resectable STS.

Imaging approaches for monitoring chemotherapy

Positron emission tomography (PET) and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) are two, often complementary, imaging modalities of great potential use for monitoring tumor therapy. They permit physiologic measures such as metabolism, perfusion, small vessel permeability and others to be made. Such measures might prove valuable supplements to the usual morphologic measures now commonly used. We give here an overview of some of the salient features of both methodologies for making such physiologic measurements.:

Weichteilsakrome

Soft tissue sarcomas are characterized by their heterogeneity. With new diagnostic imaging techniques, low- and high-grade components of the tumor can be differentiated. Thus biopsies should be guided by imaging to assure representative specimens. Besides histopathology, the advent of chromosomal and gene expression analysis may allow more accurate classification in the near future. Gene expression profiling has already proven its value by finding new subclassifications in other tumor types. Furthermore, this technique is a promissing tool to predict the response of a tumor to neoadjuvant and adjuvant therapy. Up to now, response evaluation in neoadjuvant therapy is based on tumor size and not on vital tumor cells. Newer techniques (i.e., Magnetic-resonance-Spectroscopy, Molecular Imaging) can show the change of metabolism in neoadjuvant therapy and allow objective, comparative measurement of biological activity. The diagnostic of soft tissue sarcomas implies primarily a multidisciplinary approach for a stage associated therapy.

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.

Effects of ROI definition and reconstruction method on quantitative outcome and applicability in a response monitoring trial

PURPOSE

Quantitative measurement of tracer uptake in a tumour can be influenced by a number of factors, including the method of defining regions of interest (ROIs) and the reconstruction parameters used. The main purpose of this study was to determine the effects of different ROI methods on quantitative outcome, using two reconstruction methods and the standard uptake value (SUV) as a simple quantitative measure of FDG uptake.

METHODS

Four commonly used methods of ROI definition (manual placement, fixed dimensions, threshold based and maximum pixel value) were used to calculate SUV (SUV([MAN]), SUV15 mm, SUV50, SUV75 and SUVmax, respectively) and to generate "metabolic" tumour volumes. Test-retest reproducibility of SUVs and of "metabolic" tumour volumes and the applicability of ROI methods during chemotherapy were assessed. In addition, SUVs calculated on ordered subsets expectation maximisation (OSEM) and filtered back-projection (FBP) images were compared.

RESULTS

ROI definition had a direct effect on quantitative outcome. On average, SUV[MAN), SUV15 mm, SUV50 and SUV75, were respectively 48%, 27%, 34% and 15% lower than SUVmax when calculated on OSEM images. No statistically significant differences were found between SUVs calculated on OSEM and FBP reconstructed images. Highest reproducibility was found for SUV15 mm and SUV[MAN] (ICC 0.95 and 0.94, respectively) and for "metabolic" volumes measured with the manual and 50% threshold ROIs (ICC 0.99 for both). Manual, 75% threshold and maximum pixel ROIs could be used throughout therapy, regardless of changes in tumour uptake or geometry. SUVs showed the same trend in relative change in FDG uptake after chemotherapy, irrespective of the ROI method used.

CONCLUSION

The method of ROI definition has a direct influence on quantitative outcome. In terms of simplicity, user-independence, reproducibility and general applicability the threshold-based and fixed dimension methods are the best ROI methods. Threshold methods are in addition relatively independent of changes in size and geometry, however, and may therefore be more suitable for response monitoring purposes.

Combined use of MRI and PET to monitor response and assess residual disease for locally advanced breast cancer treated with neoadjuvant chemotherapy

RATIONALE AND OBJECTIVES

The purpose of the study was to evaluate the hypothesis that magnetic resonance imaging (MRI) and positron emission tomography (PET) are complementary and valuable in monitoring response and assessing residual disease of locally advanced breast cancer (LABC) treated with neoadjuvant chemotherapy. We sought to determine if the combination of the two modalities was more accurate than either alone and could provide better guidance in patient management.

MATERIALS AND METHODS

Sixteen lesions in 15 women with LABC were evaluated with MRI, PET, and clinical breast examination (CBE) before and after neoadjuvant chemotherapy. The pre- and posttherapy maximal tumor sizes on MRI and CBE and standard uptake values (SUVs) on PET served as the measurements for clinical response classification and residual disease assessment. Pathologic assessment provided the reference for macroscopic and microscopic pathologic tumor response and residual disease.

RESULTS

PET correctly predicted lack of pathologic response in five of six cases (83%); CBE predicted correctly in one of six (17%) cases, and MRI predicted correctly in zero of six cases. When PET predicted response, MRI defined the extent of macroscopic pathologic residual disease accurately in 9 of 10 cases (90%). When posttherapy MRI showed complete response (CR) in eight cases, macroscopic pathologic complete response (mCR) was observed in all eight cases (100%).

CONCLUSION

Our study suggests that combined use of MRI and PET is complementary and offers advantages over CBE. PET was more accurate in predicting pathologic nonresponse. Complete response by MRI correlated well with macroscopic pathologic complete response.

FDG-PET scan in local follow-up of irradiated head and neck squamous cell carcinomas

We performed a prospective study to assess the value of positron emission tomography (PET) with 2-[18F]-fluoro-2-deoxy-D-glucose (FDG) in the prediction of local control in irradiated head and neck squamous cell carcinomas (HNSCCs). Forty-two patients with irradiated HNSCCs underwent 49 FDG-PET scans between 3 and 6 months after the end of radiotherapy. The mean follow-up time after the first FDG-PET scan was 17 months. The result of the FDG-PET scan was true-positive in 6 patients, false-positive in 7 patients, and true-negative in 29 patients. The sensitivity, specificity, positive predictive value, and negative predictive value of FDG-PET scanning were 100%, 81%, 46%, and 100%, respectively. We conclude that FDG-PET scanning is useful for prediction of therapy outcome in irradiated HNSCCs. No biopsy is needed for at least 1 year if an FDG-PET scan is negative. If the scan is positive and the biopsy is negative, decreased FDG uptake measured in a follow-up scan indicates that a local recurrence is unlikely.

The value of PET, CT and in-line PET/CT in patients with gastrointestinal stromal tumours: long-term outcome of treatment with imatinib mesylate

Purpose

Gastrointestinal stromal tumours (GIST) are mesenchymal neoplasms of the gastrointestinal tract that are unresponsive to standard sarcoma chemotherapy. Imaging of GIST patients is done with structural and functional methods such as contrast-enhanced helical computed tomography (ceCT) and positron emission tomography (PET) with ¹⁸F-fluorodeoxyglucose (FDG). The aim of this study was to compare the prognostic power of PET and ceCT and to evaluate the clinical role of PET/CT imaging.

Methods

All patients with GIST undergoing PET or PET/CT examinations were prospectively included in this study, and the median overall survival, time to progression and treatment duration were documented. The prognostic significance of PET and ceCT criteria of treatment response was assessed and PET/CT was compared with PET and ceCT imaging. Data for 34 patients (19 male, 15 female, 21–76 years) undergoing PET or PET/CT for staging or restaging were analysed.

Results

In 28 patients, PET/CT and ceCT were available after introduction of treatment with the tyrosine kinase inhibitor imatinib mesylate (Gleevec; Novartis, Basel, Switzerland). Patients without FDG uptake after the start of treatment had a better prognosis than patients with residual activity. In contrast, ceCT criteria provided insufficient prognostic power. However, more lesions were found on ceCT images than on PET images, and FDG uptake was sometimes very variable. PET/CT delineated active lesions better than did the combination of PET and ceCT imaging.

Conclusion

Both PET and PET/CT provide important prognostic information and have an impact on clinical decision-making in GIST patients. PET/CT precisely delineates lesions and thus allows for the correct planning of surgical interventions.

Bronchioalveolar Cell Carcinoma: Radiologic Appearance and Dilemmas in the Assessment of Response

Bronchioalveolar cell carcinomas (BACs), a subset of primary lung adenocarcinomas, are uncommon. Histologically, they are a diverse group of malignancies. The diagnosis is restricted to adenocarcinomas that grow in a lepidic manner and that have no stromal, vascular, or pleural invasion. Their histologic diversity leads to varied radiologic manifestations that are often indistinguishable from those of other primary non-small-cell lung cancers (NSCLC). However, typical manifestations, many of which can be attributed to lepidic growth, have been reported. Radiologic manifestations include a solitary peripheral pulmonary nodule, airspace disease, and multiple nodules and a combination of these findings can be present in a single patient. The most common manifestation, a solitary pulmonary nodule, is usually indistinguishable from other primary NSCLC. However, pseudocavitation and air bronchograms within the nodule can be useful in suggesting the correct diagnosis. In addition to aiding in the diagnosis of BAC, radiologic imaging is an important component in the evaluation of the therapeutic efficacy of treatment; serial measurements of tumor size before and after treatment are commonly used to assess response. However, BACs that are consolidative or ground-glass in nature present challenges in tumor-response determination. Other imaging modalities, such as positron emission tomography scanning, may prove helpful in assessing the metabolic response to therapy but have yet to be proven effective.

FDG PET and high-dose therapy for aggressive lymphomas: toward a risk-adapted strategy

PURPOSE OF REVIEW

Functional metabolic imaging through fluorine-18 fluorodeoxyglucose positron emission tomography has recently come to the forefront in the management of various solid and hematologic malignancies. This review summarizes the developments in risk assessment through positron emission tomography in patients with lymphoma and the implications for management.

RECENT FINDINGS

In addition to improving staging and response assessment, positron emission tomography has emerged as a strong prognostic tool in patients with aggressive lymphomas. A positron emission tomographic scan performed after only a few cycles of chemotherapy can accurately predict relapse risk, and most studied patients with abnormal positron emission tomographic scans have had distinctly poorer clinical outcomes than patients with negative scans.

SUMMARY

With confirmation of these findings, a more individualized, risk-adapted approach to the treatment of aggressive lymphomas will be feasible. Early identification of high-risk patients through the combination of positron emission tomography and existing prognostic indices could lead to earlier implementation of intensive therapies and improved clinical outcomes.

Sequential preoperative fluorodeoxyglucose-positron emission tomography assessment of response to preoperative chemoradiation: a means for determining longterm outcomes of rectal cancer

BACKGROUND

We have previously demonstrated that fluorodeoxyglucose-positron emission tomography (FDG-PET) can assess extent of pathologic response of primary rectal cancer to preoperative chemoradiation. Our goal was to determine the prognostic significance of FDG-PET assessment of rectal cancer response to preoperative chemoradiation.

STUDY DESIGN

Fifteen patients with locally advanced primary rectal cancer (clinically bulky or tethered, or ultrasound evidence of T3-4 disease, N1 disease, or both) deemed eligible for preoperative radiation and 5-FU-based chemotherapy (5,040 cGy to the pelvis and 2 cycles of bolus 5-FU/leucovorin) were prospectively enrolled from May 1997 to September 1998. FDG-PET was performed before and 4 to 5 weeks after completion of preoperative chemoradiation. FDG-PET parameters included maximum standard uptake value (SUV(max)), total lesion glycolysis (TLG), and visual response score. Patients were prospectively followed after operation, and disease status was determined.

RESULTS

All patients demonstrated some degree of response to preoperative therapy based on pathologic examination. At a median followup of 42 months (range 23 to 54 months), 11 patients had no evidence of disease and 4 had died of disease. The mean percentage decrease in SUV(max) (DeltaSUV(max)) was 69% for patients free from recurrence and 37% for patients with recurrence (p = 0.004). DeltaSUV(max) >or= 62.5 and deltaTLG >or= 69.5 were the best predictors of no-evidence-of-disease status and freedom from recurrence. Patients with DeltaSUV(max) >or= 62.5 and deltaTLG >or= 69.5 had significantly improved disease-specific and recurrence-free survival (p = 0.08, 0.02 and p = 0.03, 0.01, respectively).

CONCLUSIONS

Our results indicate that FDG-PET assessment of locally-advanced rectal cancer response to preoperative chemoradiation may predict longterm outcomes.