Characteristics of Brain Metastases Identified by PET-CT Imaging in Patients with Lung Cancer

Contrast enhanced magnetic resonance imaging (MRI) could not be performed in all patients due to some contraindications. We aimed to demonstrate the characteristics of brain metastases that could be diagnosed with positron emission tomography - computed tomography (PET-CT) among patients with lung cancer.

Four hundred thirty nine patients diagnosed with lung cancer and brain metastasis between 2019 and 2023 were evaluated. A total of 642 brain metastasis lesions were identified, of which 286 were detectable on PET-CT. Univariate and multivariate logistic regression analyses were used to identify independent predictors of PET-CT positivity.

Out of all patients, 86.6% were male and the mean ± SD age was 64.8±9.3. Comorbidities were present in 205 patients (46.7%), with chronic obstructive pulmonary disease (COPD) being the most prevalent (27.1%). The majority of metastases were located in the frontal lobe (37.2%) followed by the parietal lobe (26.6%). Notably, PET-CT negative lesions were more likely to have peritumoral edema than PET-CT positive lesions had (67% vs. 56%, p=0.004). The median tumor diameter for PET-CT positive lesions was larger than PET-CT negative lesions (18 vs 10 mm, p<0.001). The discriminative accuracy of tumor diameter in predicting PET-CT positivity was found to be high, with an area under the curve (AUC) of 0.70 (95% CI: 0.65 to 0.73). For an optimal cut-off value of 14 mm, sensitivity of tumor diameter was 71.68% and specificity was 58.71.

Brain metastases larger than 14 mm and those without peritumoral edema tend to have increased detectability with PET-CT in a large group of lung cancer patients. Since the diagnostic role of PET-CT could not be fully analyzed due to the study design, further research including patients without brain metastases is recommended.