Silent brain metastasis in the initial staging of lung cancer:: Evaluation by computed tomography and magnetic resonance imaging

OBJECTIVE: Brain metastases are common in patients with lung cancer and influence both prognosis and treatment decisions. The aim of this study was to evaluate the incidence of silent brain metastasis during the initial staging of lung cancer using cranial computed tomography (CT) and magnetic resonance imaging (MRI). PATIENTS AND METHODS: We performed a retrospective analysis of lung cancer patients with no neurologic signs or symptoms who were evaluated by cranial CT, MRI, or both at the time of diagnosis. Results were checked using data obtained during systematic monitoring of progression. The incidence of brain metastasis was analyzed by sex, age, histology, and TNM stage. RESULTS: Silent brain metastasis was detected in 8.3% of the 169 patients with lung cancer. The detection rate was 7.9% in the cranial CT group and 11.3% in the cranial MRI group. The percentage of false positives and false negatives was 0% and 1.9%, respectively. Cranial MRI performed better than CT in detecting multiple brain metastases (72.8% vs 50%) and metastases smaller than 1 cm (36.3% vs 16.7%). The incidence of brain metastasis was lower in patients aged over 70 years and higher in patients with adenocarcinoma (20% compared to 5.3% to 5.9% for other histologic subtypes, P=.01). No association was found with TNM stage. CONCLUSIONS: The incidence of silent brain metastasis is high in patients under 70 years of age, particularly in patients with adenocarcinomas, even in initial stages. This should be taken into consideration when planning staging procedures. Cranial MRI seems to be more accurate than cranial CT for detecting multiple metastases and small metastases.