Follow up results of a prospective study to evaluate the impact of FDG-PET on CT-based radiotherapy treatment planning for oesophageal cancer.

BACKGROUND: This prospective study aims to determine the impact of PET/CT on radiotherapy planning and outcomes in patients with oesophageal cancer. METHODS: All patients underwent PET/CT scanning in the radiotherapy treatment position, and received treatment planned using the PET/CT dataset. GTV was defined separately on PET/CT (GTV-PET) and CT (GTV-CT) datasets. A corresponding PTV was generated for each patient. Volumetric and spatial analysis quantified the proportion of FDG-avid disease not included in CT-based volumes. Clinical data was collected to determine locoregional control and overall survival rates. RESULTS: 13 (24.1%) of 57 accrued patients had metastatic disease detected on PET. Median follow up was 4 years. FDG-avid disease would have been excluded from GTV-CT in 29 of 38 patients (76%). In 5 patients, FDG-avid disease would have been completely excluded from the PTV-CT. GTV-CT underestimated the cranial and caudal extent of FDG-avid tumour in 14 (36%) and 10 (26%) patients. 4-Year overall survival and locoregional failure free survival were 37% and 65%. CONCLUSIONS: PET/CT altered the delineation of tumour volumes when compared to CT alone, and should be considered standard for treatment planning. Although clinical outcomes were not improved with PET/CT planning, it did allow the use of smaller radiotherapy volumes.

Modern diagnostic and therapeutic interventional radiology in lung cancer.

Imaging has an important role in the multidisciplinary management of primary lung cancer. This article reviews the current state-of-the-art imaging modalities used for the evaluation, staging and post-treatment follow-up and surveillance of lung cancers, and image-guided percutaneous techniques for biopsy to confirm the diagnosis and for local therapy in non-surgical candidates.

Comparative PET study using F-18 FET and F-18 FDG for the evaluation of patients with suspected brain tumour.

The aim of this prospective pilot study in patients with suspected or known brain tumour was to establish the diagnostic value of O-(2-[(18)F]-fluoroethyl)-L-tyrosine (FET) positron emission tomography (PET) when compared to fluorine-18 fluorodeoxyglucose (FDG) PET. Twenty-five FET PET and FDG PET scans were performed on 21 consecutive patients within 24 months. Final malignant pathology included 11 glioma (eight low-grade, three high grade), two lymphoma, one olfactory ganglioneuroblastoma, one anaplastic meningioma. Benign pathology included two encephalitis and one cortical dysplasia. Definitive pathology was not available in three patients. The accuracy of PET was determined by subsequent surgical histopathology in 12 and clinical/imaging course in nine patients. Median follow-up period was 20 months. FET sensitivity was 93%, specificity 100%, accuracy 96%, positive predictive value (PPV) 100% and negative predictive value (NPV) 91%. FDG sensitivity was 27%, specificity 90%, accuracy 52%, PPV 80% and NPV 45%. FET PET is more accurate than FDG PET for detecting malignant brain lesions, especially low-grade gliomas.

PET/MRI: a different spin from under the rim.

INTRODUCTION: Hybrid imaging is now widely accepted in cancer imaging with increasing use of PET/CT in clinical practice. The advantages of MRI compared to CT with respect to radiation exposure and soft-tissue lesion contrast, as well as the possibility of performing more sophisticated assessment of tissue chemistry, have stimulated interest in the development of hybrid PET/MR imaging systems. OBJECTIVE: While PET/CT simultaneously increases diagnostic quality and patient throughput compared to PET, offsetting the higher cost of this instrumentation, PET/MRI will likely be more expensive again and is currently unlikely to be competitive in terms of throughput. DISCUSSION: To realize the unique potential advantages of combined PET/MRI, we believe that PET/MRI devices should be designed to be a complementary tool running in parallel with PET/CT. The use of PET/CT for whole-body screening could identify lesions requiring more detailed anatomical and biological characterization. Selection of only those patients and those lesions for which this information is critical for treatment selection and planning will provide efficient and easily justified use of what will, for the foreseeable future, be an expensive and limited resource.

Abdominal manifestations of extranodal lymphoma: spectrum of imaging findings.

OBJECTIVE: The purpose of this article is to illustrate the spectrum of appearances of extranodal lymphoma in the abdomen using cross-sectional imaging techniques. CONCLUSION: Extranodal lymphoma in the abdomen can mimic other neoplastic or inflammatory conditions. Although a definitive diagnosis is possible only with biopsy, it is important to consider extranodal lymphoma in the presence of certain imaging appearances in the appropriate clinical setting for the correct diagnosis, accurate staging, and optimal management.

Atypical brown fat distribution in young males demonstrated on PET/CT.

The development of PET/CT has led to the recognition that metabolically active fat, referred to as "brown fat," can accumulate FDG and represents a possible source of false-positive scans in oncology patients. Numerous reports have described the typical appearance of brown fat, which most commonly presents as neck and paravertebral uptake in young female patients. Other described sites of uptake include the mediastinum and retroperitoneum. We present examples of 2 cases of atypical diffuse brown fat uptake seen in the subcutaneous fat of the thighs, abdomen, and pelvis. Both of these patients were young men and did not show uptake in the typical supraclavicular and neck fat. Although rare in our experience, knowledge of this condition may prevent misinterpretation of this finding as an infiltrative condition of the skin, such as lymphoma.

[Clinical application of (18)F-FDG PET/CT to staging and treatment effectiveness monitoring of nasopharyngeal carcinoma].

BACKGROUND & OBJECTIVE: Fluorine-18 fluorodeoxyglucose ((18)F-FDG) PET/CT could increase the accuracy of diagnosis, staging, and treatment effectiveness monitoring of many malignant diseases, such as lung cancer and esophageal cancer. This study was to evaluate the clinical application of (18)F-FDG PET/CT to the staging, restaging, and treatment effectiveness monitoring of nasopharyngeal carcinoma (NPC). METHODS: The reports of whole body (18)F-FDG PET/CT scans, performed from Feb. 2002 to Dec. 2005 on 43 NPC patients (26 men and 17 women with median age of 52 years) in Peter MacCallum Cancer Center, were reviewed. The final diagnoses were made according to medical records, pathologic reports and follow-up information. The accuracy, specificity, sensitivity, positive predictive value (PPV), and negative predictive value (NPV) of (18)F-FDG PET/CT, CT and MRI were calculated and analyzed. RESULTS: The accuracy, specificity, sensitivity, PPV, and NPV of (18)F-FDG PET/CT were 95.3%, 100.0%, 85.7%, 93.8%, and 100.0%, respectively; those of CT and MRI were 65.5%, 79.4%, 64.7%, 81.8%, and 57.9%, respectively. The results of (18)F-FDG PET/CT led to changes in the medical management of 2 staged patients, and 7 restaged patients and 5 patients in monitoring group. (18)F-FDG PET/CT scan affected the therapy plan of 3 restaged patients and 11 patients in monitoring group. Two cases of second primary malignancies(1 case of thyroid carcinoma and 1 case of low grade gastric carcinoma) were detected by (18)F-FDG PET/CT scan. CONCLUSION: (18)F-FDG PET/CT is better than conventional imaging in N and M staging and treatment effectiveness monitoring of NPC.

How do oncologists deal with incidental abnormalities on whole-body fluorine-18 fluorodeoxyglucose PET/CT?

BACKGROUND: Combined positron emission tomography (PET)/computed tomography (CT) using fluorine-18 fluorodeoxyglucose (FDG) is an exciting technique for cancer evaluation, but false-positive results are a recognized limitation. The aim of the study was to evaluate how oncologists deal with focal extrathyroidal FDG abnormalities considered by imaging specialists to be unrelated to the referral indication. METHODS: PET scan reports from a 12-month period from August 2002 to July 2003 in 1727 consecutive patients (mean age, 63 years) were reviewed. Incidental, nonphysiologic FDG abnormalities were classified based on the report conclusion. The frequency with which such abnormalities were investigated by oncologists and the final diagnosis were compared with the imaging diagnosis with a minimum potential follow-up of 2 years (mean, 27.5 months). RESULTS: Incidental FDG abnormalities were reported in 199 (12%) of 1727 patients, including 181 with adequate follow-up. Of 59 cases with a suspected second malignancy, 34 (58%) were actively investigated, with 14 confirmed, 7 unexpected metastatic sites, and 10 other active pathologies. Only 1 further cancer was subsequently detected in the 25 (42%) patients not actively investigated. Conversely, of 122 sites presumed to be benign, only 10 (8%) were actively investigated. Only 2 were proven to relate to malignancy. CONCLUSIONS: Although incidental abnormalities were common, most were benign and appropriately categorized by experienced readers. For actively investigated extrathyroidal abnormalities, a neoplastic basis was confirmed in over 60% of cases. Conversely, for cases deemed most likely benign by the PET/CT report or after review of readily available clinical information by the referring oncologist, the rate of malignancy was less than 2%.

PET/CT: will it change the way that we use CT in cancer imaging?

Accurate staging of cancer is of fundamental importance to treatment selection and planning. Current staging paradigms focus, first, on a detailed delineation of the primary tumour in order to determine its suitability for resection, and, thereafter, on assessment of the presence of metastatic spread that would alter the surgical approach, or mandate non-surgical therapies. This approach has, at its core, the assumption that the best, and sometimes the only, way to cure a patient of cancer is by surgical resection. Unfortunately, all non-invasive techniques in current use have imperfect ability to identify those primary tumours that are able to be completely excised, and even worse ability to define the extent of metastatic spread. Nevertheless, because of relatively low cost and widespread availability, computed tomography (CT) scanning is the preferred methodology for tumour, nodal and systemic metastasis (TNM) staging. This is often supplemented by other tests that have improved performance in particular staging domains. For example, magnetic resonance imaging (MRI), mammography, or endoscopic ultrasound may be used as complementary tests for T-staging; surgical nodal sampling for N-staging; and bone scanning, MRI or ultrasound for M-staging. Accordingly, many patients undergo a battery of investigations but, even then, are found to have been incorrectly staged based on subsequent outcomes. Even for those staged surgically, pathology can only identify metastases within the resection specimens and has no capability for detecting remote disease. As a result of this, many patients undergo futile operations for disease that could never have been cured by surgery. In the case of restaging, the situation is even worse. The sequelae of prior treatment can be difficult to differentiate from residual cancer and the likelihood of successful salvage therapy is even less than at presentation. More deleteriously, patients may be subjected to additional morbid treatments when cure has already been achieved. Thus, in post-treatment follow-up, the presence and extent of disease is equally critical to treatment selection and patient outcome as it is in primary staging. One of the major strengths of positron emission tomography (PET)/CT as a cancer staging modality is its ability to identify systemic metastases. At any phase of cancer evaluation, demonstration of systemic metastasis has profound therapeutic and prognostic implications. Only in the absence of systemic metastasis does nodal status become important, and only when unresectable nodal metastasis has been excluded does T-stage become important. There are now accumulating data that PET/CT could be used as the first, rather than the last test to assess M- and N-stage for evaluating cancers with an intermediate to high pre-test likelihood of metastatic disease based on poor long-term survival. In this scenario, there is great opportunity for subsequently selecting and tailoring the performance of anatomically based imaging modalities to define the structural relations of abnormalities identified by PET, when this information would be of relevance to management planning. Primary staging of oesophageal cancer and restaging of colorectal cancer are illustrative examples of a new paradigm for cancer imaging.

A prospective study to evaluate the impact of FDG-PET on CT-based radiotherapy treatment planning for oesophageal cancer.

BACKGROUND AND PURPOSE: This prospective study sought to determine how the use of combined PET/CT for radiotherapy treatment planning of oesophageal cancer would alter the delineation of tumour volumes compared to CT alone if PET/CT is assumed to more accurately represent true disease extent. PATIENTS AND METHODS: All patients underwent FDG-PET/CT scanning in the radiotherapy treatment position. For each patient, two separate gross tumour volumes (GTV) were defined, one based on CT images alone (GTV-CT) and another based on combined PET/CT data (GTV-PET). Corresponding planning target volumes (PTV) were generated, and separate treatment plans were then produced. For each patient, volumetric analysis of GTV-CT, PTV-CT and GTV-PET was performed to quantify the proportion of PET-avid disease that was not included in the GTV and PTV (geographic miss) if CT data alone were used for radiotherapy planning. Assessment of the cranial and caudal extent of the primary oesophageal tumour as defined by CT alone vs PET/CT was also compared. RESULTS: The addition of PET information altered the clinical stage in 8 of 21 eligible patients enrolled on the study (38%); 4 patients had distant metastatic disease and 4 had unsuspected regional nodal disease. Sixteen patients proceeded to the radiotherapy planning phase of the study and received definitive chemoradiation planned with the PET/CT data set. The GTV based on CT information alone excluded PET-avid disease in 11 patients (69%), and in five patients (31%) this would have resulted in a geographic miss of gross tumour. The discordance between CT and PET/CT was due mainly to differences in defining the longitudinal extent of disease in the oesophagus. The cranial extent of the primary tumour as defined by CT vs PET/CT differed in 75% of cases, while the caudal extent differed in 81%. CONCLUSIONS: This study demonstrates that if combined PET/CT is used for radiotherapy treatment planning, there may be alterations to the delineation of tumour volumes when compared to CT alone, with the potential to avoid a geographic miss of tumour.