Abstract
Positron emission tomography (PET) imaging with 2-deoxy-2-[18F]-fluorodeoxyglucose (FDG) was proposed as prognostic marker in radiotherapy. Various uptake metrics and cut points were used, potentially leading to inflated effect estimates. Here, we performed a meta-analysis and systematic review of the prognostic value of pretreatment FDG–PET in head and neck squamous cell carcinoma (HNSCC) and non-small cell lung cancer (NSCLC), with tests for publication bias. Hazard ratio (HR) for overall survival (OS), disease free survival (DFS), and local control was extracted or derived from the 57 studies included. Test for publication bias was performed, and the number of statistical tests and cut-point optimizations were registered. Eggers regression related to correlation of SUVmax with OS/DFS yielded p = 0.08/p = 0.02 for HNSCC and p < 0.001/p = 0.014 for NSCLC. No outcomes showed significant correlation with SUVmax, when adjusting for publication bias effect, whereas all four showed a correlation in the conventional meta-analysis. The number of statistical tests and cut points were high with no indication of improvement over time. Our analysis showed significant evidence of publication bias leading to inflated estimates of the prognostic value of SUVmax. We suggest that improved management of these complexities, including predefined statistical analysis plans, are critical for a reliable assessment of FDG–PET.
Highlights
Positron emission tomography (PET) offers a non-invasive method to assess functional biological characteristics of a tumor in an individual patient with cancer
FDG–PET imaging is primarily used for staging purposes, as a supplement to anatomical images, but advances in the availability of PET imaging led to an increased interest in the feasibility of PET guided radiotherapy planning [8]
We reviewed the methodology of published studies of the prognostic value of FDG in head and neck squamous cell carcinoma (HNSCC) and non-small cell lung cancer (NSCLC), and assessed the evidence of publication bias
Summary
Positron emission tomography (PET) offers a non-invasive method to assess functional biological characteristics of a tumor in an individual patient with cancer. Several studies investigated the prognostic value of FDG–PET, and dose escalation to PET-positive areas within the tumor is one of the potential strategies for increasing effect of radiotherapy [9–12]. Despite the widespread use of FDG, only few prospective studies exist for this tracer—the value of FDG as prognostic factor was mainly tested in retrospective cohort studies, for example [13]. The lack of prospective clinical studies with study registration, formalized sample size estimation and a predefined statistical analysis plans. All of this leads to a risk of “fishing expeditions” with a high risk of false positive findings, exaggerated effect sizes, and subsequent publication bias. Multiple testing is a well-described contributor to false positive findings; when comparisons are made for several subgroups or multiple variables, without adjustment of the type I error rate (false positives)
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