Detection of the primary tumor has a key role in the management of patients with unknown primary tumors (UPT). The aim of this study was to perform a meta-analysis of the literature to evaluate the accuracy of (18)F-FDG PET in primary tumor detection in patients with UPT.
Methods: Systematic methods were used to identify, select, and evaluate the methodologic quality of the studies as well as to summarize the overall findings of sensitivity, specificity, and detection capacity of the primary tumor. The search strategy consisted of identifying studies published between January 1994 and May 2001 indexed in MEDLINE and CANCERLIT. Studies identified by manually searching reference lists of retrieved studies or by reviewing abstracts from recent conference proceedings were also included. Inclusion criteria were studies that evaluated primary tumor detection with (18)F-FDG PET in patients with UPT. Exclusion criteria were duplicated studies or those outdated by subsequent ones. The statistical analysis included 95% confidence intervals (CI) of sensitivity and specificity, both in the pooled data and in the types of studies found. Variation in accuracy between studies was analyzed calculating the natural logarithm of the odds ratio (ln OR) due to study characteristics. Funnel plots of sensitivity and specificity and the summary receiver-operating-characteristic (ROC) curve were also represented.
Results: Fifteen studies met the inclusion criteria and were analyzed. Although sample sizes were small, compliance with the methodologic quality criteria was adequate. Heterogeneity analysis showed that differences in the study quality did not correlate with differences in study results. The 95% CI of sensitivity and specificity presented global homogeneity, estimating the sensitivity at 0.87 (95% CI, 0.81-0.92) and the specificity at 0.71 (95% CI, 0.64-0.78). The summary ROC curve showed a good relationship between sensitivity and specificity. The ln OR presented significant values in >75% of the studies.
Conclusion: (18)F-FDG PET could be useful in patients with UPT for the detection of the primary tumor. (18)F-FDG PET has intermediate specificity and high sensitivity, indicating the existence of few false-negative results, an important feature in the management of oncologic patients that could suggest its utility in the initial stages of the management process.