Magnetic resonance imaging characteristics of brain metastases in small cell lung cancer

BACKGROUND: Lung is the most common primary site of brain metastases (BMs). For different pathological types of BMs have some similar characteristics, it is still a challenge to confirm the origin based on their characteristics directly. BMs of small cell lung cancer (SCLC) have favorable therapeutic expectations due to their high sensitivity to radiotherapy. This study sought to identify unique characteristics of BMs in SCLC, aiming to assist in clinical decision‐making. METHODS: Patients diagnosed with BMs of lung cancer who received radiotherapy from January 2017 to January 2022 were reviewed (N = 284). Definitive diagnosis of BMs of SCLC was reached for 36 patients. All patients underwent head examination using magnetic resonance imaging. The number, size, location, and signal characteristics of lesions were analyzed. RESULTS: There were 7 and 29 patients with single focus and non‐single focus, respectively. Ten patients had diffuse lesions, and the remaining 26 patients had a total of 90 lesions. These lesions were divided into three groups according to size: <1, 1–3, and >3 cm (43.33%, 53.34%, and 3.33%, respectively). Sixty‐six lesions were located in the supratentorial area, primarily including cortical and subcortical lesions (55.56%) and deep brain lesions (20%). Moreover, 22 lesions were located in the infratentorial area. According to diffusion‐weighted imaging and T1‐weighted contrast enhancement, the imaging characteristics were classified into six patterns. Hyperintensity in diffusion‐weighted imaging and homogeneous enhancement was the most common pattern of BMs in SCLC (46.67%), while partial lesions showed hyperintensity in diffusion‐weighted imaging without enhancement (7.78%). CONCLUSIONS: The manifestations of BMs in SCLC were multiple lesions (diameter: 1–3 cm), hyperintensity in diffusion‐weighted imaging, and homogeneous enhancement. Interestingly, hyperintensity in diffusion‐weighted imaging without enhancement was also one of the characteristics.