Retrospective study of qualitative assessment in detecting synchronous and metachronous malignancies in adult cancer patients by 18F-FDG PET/CT.

OBJECTIVES: The study aimed to evaluate the frequency of incidental suspicious lesions detected by flourine-18 fluorodeoxyglucose PET/computed tomography (18F-FDG PET/CT) scans done for staging or restaging in adult cancer patients. We further determined the detection rate of synchronous and metachronous malignancies in these suspicious lesions after further investigations. MATERIALS AND METHODS: This retrospective analysis evaluated the consecutive patients with 18F-FDG PET/CT scans done in Queen Elizabeth Hospital (QEH), Hong Kong between July 2021 and June 2022. The adult cancer patients who underwent staging or restaging 8F-FDG PET/CT were included while the remaining were excluded. Patients' demographics, primary cancer type, tumor markers, and pathological analyses for the incidental suspicious lesions were reviewed to establish the detection rate of synchronous and metachronous malignancies. RESULTS: A total of 2054 patients fulfilled inclusion criteria with age ranging from 18 to 93 years old. Out of the 2054 patients, 304 (14.8%) were found to have incidental suspicious lesions. Of these, 206 patients (67.8%) underwent further investigations including pathological analyses. Subsequently, 84 of these 206 patients (40.8%) had pathologically proven synchronous or metachronous malignancies. CONCLUSION: The detection rate of incidental suspicious lesions in adult cancer patients who underwent 18F-FDG PET/CT scans for staging or restaging was 14.8% and the rate of synchronous and metachronous malignancies in these suspicious lesions was 40.8%. The treatment plan of these patients may potentially be altered, which should be included in the cost-benefit analysis of using this imaging modality.

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

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.