The diagnostic performance of 18 fluorine-fluorodeoxyglucose PET for brain metastases: a systematic review and meta-analysis

Abstract

Introduction: Brain metastases may manifest as hypermetabolism or hypometabolism compared with normal brain activity on 18 fluorine-fluorodeoxyglucose PET ( 18 F-FDG PET). We aim to undertake a systematic review and meta-analysis to determine the diagnostic accuracy of FDG PET for detecting brain metastases from different extracranial primary cancers.

Methods: PubMed and EMBASE were searched systematically. Study selection and quality assessment were performed independently by two authors. Meta-analysis was performed using a bivariate random-effects model. Subgroup analysis and meta-regression would be performed if heterogeneity was found.

Results: A total of 2227 patients from 11 studies were included in the review and analysis. Using the bivariate random-effects model, summary patient-based sensitivity and specificity for all 11 studies were estimated to be 0.440 [95% confidence interval (CI)] 0.295-0.597) and 0.997 (95% CI, 0.977-1.000). In view of significant between-study heterogeneity ( I2 = 74.0% for sensitivity and I2 = 67.3% for specificity), subgroup analyses were performed. Meta-regression showed significantly higher patient-based summary sensitivity for the three better-quality studies (a total of 1037 patients) with satisfactory index test (counting both hypermetabolism and hypometabolism as positive index test) and satisfactory reference standards (other imaging and clinical follow-up) compared with other included studies [0.735 (95% CI, 0.601-0.836) vs 0.304 (95% CI, 0.223-0.400), P value = 0.000].

Conclusion: Our systematic review and meta-analysis showed that FDG PET has overall limited sensitivity and excellent specificity in the detection of brain metastases from extracranial primary cancers. Importantly, subgroup analyses showed that the sensitivity can be significantly improved by raising awareness of asymmetrical hypometabolism. Further studies are warranted to assess the benefits of including the brain in FDG PET studies for all or certain groups of oncological patients.