Positron emission tomography Medicare Services Advisory Committee

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1 Positron emission tomography Medicare Services Advisory Committee Authors' objectives To assess the effectiveness of positron emission tomography (PET), the report addressed the following (truncated) six questions pertinent to current practice in Australia. What is the value of pre-operative PET plus usual staging versus usual staging alone in potentially curable non-smallcell lung cancer (NSCLC)? Can PET define the role of surgery in potentially resectable malignant melanoma? What is the value of PET in distinguishing residual cerebral tumour after treatment for malignant glioma? What is the value of PET in evaluating suspected recurrent colorectal cancer? What is the value of pre-surgical PET in refractory epilepsy where there is no focus with concordant results on usual structural imaging and electroencephalography? What is the role of PET in assessing coronary revascularisation in chronic heart disease and impaired ventricular function? Searching MEDLINE was searched from 1996 to January 2000 (the search strategy was available in the report). The Cochrane Library, the NHS EED and HTA databases, and websites of health technology assessment organisations were also searched (dates not reported). Inclusion was restricted to full articles published in English in peer-reviewed journals, although abstracts appear to have been included for coronary revascularisation. Papers included in earlier systematic reviews, and papers referenced in other review articles or identified by members of the expert working party supporting this review, were also eligible for inclusion. Study selection Study designs of evaluations included in the review The general inclusion criteria specified that the studies had to report primary data, include at least 10 participants, and all consecutive patients who fulfilled the study entry criteria had to be included. The studies had to report sufficient information to judge the comparability of case and control groups, use an independent blind comparison with a reference standard, and report that the results of the PET scan did not influence the decision to perform the reference test. The studies also had to provide sufficient detail about the methods used to perform the test to permit replication. Additional criteria specific to the individual review questions were detailed in the report. Specific interventions included in the review Studies using fluoro-2-deoxy-d-glucose (FDG), dedicated PET or gamma camera systems adapted with 511 kev coincidence imaging capability were eligible. The specific criteria stated were: for NSCLC, the use of FDG whole-body PET, conventional staging including a computed tomography (CT) scan of the chest and abdomen; for epilepsy, PET prior to surgery (not after); and for coronary revascularisation, both single-photon emission CT (SPECT) and PET had to be done (or studies restricted Page: 1 / 5

2 to patients negative on SPECT). There was no clear statement about reference standards in the inclusion criteria. There was wide variation in the reference standards used in the individual primary studies. Some details were tabulated in the report. Reference standard test against which the new test was compared There was no clear statement about reference standards in the inclusion criteria. There was wide variation in the reference standards used in the individual primary studies. Some details were tabulated in the report. Participants included in the review The specific criteria stated were as follows. NSCLC: patients with known or suspected NSCLC who were candidates for curative surgery after conventional staging investigations. Melanoma: patients being evaluated for known or suspected metastatic disease, lymph node assessment or high-risk patients. Glioma: patients with suspected recurrent glioma (not primary). Colorectal cancer: patients with suspected recurrence based on clinical features, abnormal imaging or abnormal tumour markers. Epilepsy: patients with epilepsy refractory to medical treatment who were being considered for surgery. Coronary revascularisation: patients being considered for revascularisation. Those considered on SPECT to have nonviable myocardium, or where viability was uncertain, were of special interest. Outcomes assessed in the review Diagnostic accuracy and the impact on clinical decision-making and health outcomes were assessed. Inclusion criteria specific to the individual review questions were detailed in the report. How were decisions on the relevance of primary studies made? The authors did not state how the papers were selected for the review, or how many reviewers performed the selection. Assessment of study quality The report presented a list of published criteria designed to assess the validity of studies of diagnostic tests. These appear to have been used in this review, although this was not clearly stated. It was reported that the studies had been graded using a hierarchy of evidence based on study design from I (highest, systematic review of randomised trials) to IV (lowest, case series). The authors did not state how the papers were assessed for validity, or how many reviewers performed the validity assessment. Data extraction The authors did not state how the data were extracted for the review, or how many reviewers performed the data extraction. Details of the imaging protocol, whether visual or quantitative analysis of PET was used, and the type of PET quantitative analysis were extracted. The results appear to have been extracted as reported in the included studies. Methods of synthesis How were the studies combined? A narrative synthesis was used within each review question and, in some cases, within different aspects of a given question. How were differences between studies investigated? Some differences between the studies were discussed in the text. Tables of the characteristics of the included primary Page: 2 / 5

3 studies, from which differences and similarities could be compared, were presented. Results of the review All of the included primary studies appear to have been case series (explicit only for NSCLC and melanoma). The numbers of studies included per question were 17 for NSCLC, 2 for melanoma (plus 9 mainly about diagnostic accuracy rather than the stated clinical question), 16 for glioma, 5 (in addition to existing reviews) for colorectal cancer, 5 for epilepsy, and 159 for coronary revascularisation (this appears to include existing reviews and primary studies). The quality of the included studies was generally poor. Particular aspects associated with bias in studies of diagnostic tests were pointed out in the narrative summary of the findings. Preoperative staging of NSCLC: 14 case series assessed the accuracy of PET for detecting mediastinal node involvement; 2 of those studies and 3 additional studies assessed the detection of distant metastases. The diagnostic accuracy of these applications appeared to be improved when conventional imaging (CT) was used in addition to PET. The improvement could not be quantified due to various potential sources of bias in the studies. There was no direct evidence that PET improved patient outcomes. Melanoma: based on 2 case series, it was not possible to determine whether changes in patient management that resulted from PET improved patient outcomes. PET appeared to be more accurate than conventional imaging techniques in detecting metastatic disease, but the studies were of a poor quality. Glioma: no studies that reported patient outcomes arising from PET following conventional imaging were found. There was insufficient information of adequate quality to determine whether PET was superior to SPECT/SPET in distinguishing suspected recurrence from radiation necrosis. Colorectal cancer: the findings were based on previous reviews (see Other Publications of Related Interest) and 5 other subsequently published studies that were considered to be of similar quality to those included in a previous review. The concordance of PET and CT for detection of local recurrence and liver metastases was high. The sensitivity of PET was better, but there was insufficient information about how the outcomes were affected by changing management in patients with abnormalities only detectable by PET. Epilepsy: the sensitivity of presurgical PET was reported to be relatively high (no values were given). Some patients who would be helped by surgery would benefit as a result of a positive PET scan. However, there was a lack of information on patients who test negative on PET, but are willing to undergo surgery, and patients who test positive on PET and do not undergo surgery. Coronary revascularisation: it is likely that PET detects viable underperfused myocardium that would respond well to revascularisation; PET seemed to be more sensitive than SPECT. Few data were available to assess the response to revascularisation when viable myocardium was detected by PET but not SPECT. Safety: a large prospective study of the prevalence of adverse reactions reported that none occurred among 81,000 doses of positron-emitting radiopharmaceuticals (including FDG). Published evidence on the safety of the PET procedure as a whole was lacking. Cost information The review addressed cost-effectiveness. Economic modelling studies suggested that PET may be cost-effective or costsaving. However, further validation of the assumptions on which these models were based was called for. Authors' conclusions The report stated that the administration of FDG is safe, but there is insufficient evidence to inform definitive conclusions about the clinical (and cost) effectiveness of FDG PET. Page: 3 / 5

4 CRD commentary The methodological rigour expected of a systematic review of a diagnostic test was not apparent in the report. The reason may be that the report was prepared by the Australian Medicare Services Advisory Committee (MSAC), who commissioned the evidence review, and not by the reviewers themselves. The scope of the review was wide. Studies that did not address the questions directly were included in the review, but it was not entirely clear how those studies were selected; in that respect the reported inclusion criteria were imprecise. The methods used to select the studies, assess study quality and extract the data were not reported, so the potential for bias in the review process is unknown. There is a real possibility of language bias in the review; another possibility, publication bias, was not investigated. The report listed existing reviews under each question, followed by the literature review of primary studies. In some cases (e.g. colorectal cancer), the conclusions were based almost entirely on previous reviews without providing any assurance of the quality of those reviews. In most cases the included primary studies were tabulated clearly, but none of the studies concerning coronary revascularisation were shown. A narrative synthesis may have been appropriate. However, the report contained rather lengthy descriptions of studies of uncertain relevance from which no clear message arose. The implications for practice reflected the MSAC approach whereby advice was sought from an expert committee over and above the systematic review. Implications of the review for practice and research Practice: The authors stated that there was insufficient evidence to inform definitive conclusions about the clinical effectiveness of FDG PET. Nevertheless, a list of MSAC-approved indications were listed in the report. Research: The authors stated that PET needs further evaluation. Ongoing studies were mentioned in relation to some of the questions addressed. Bibliographic details Medicare Services Advisory Committee. Positron emission tomography. Canberra, ACT, Australia: Medicare Services Advisory Committee. Final assessment report Original Paper URL Other publications of related interest Adams E, Asua J, Conde Olasagasti J, Erlichman M, Flynn K, Hurtado-Saracho I, on behalf of INAHTA. Positron Emission tomography: experience with PET and synthesis of the evidence. Stockholm, Sweden: INAHTA Indexing Status Subject indexing assigned by CRD MeSH Tomography, Emission-Computed AccessionNumber Date bibliographic record published 31/03/2004 Date abstract record published 31/03/2004 Record Status This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract Page: 4 / 5

5 Powered by TCPDF ( contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn. Page: 5 / 5