The current study was performed to investigate the frequency of leptomeningeal metastases (LMM) in patients with small cell lung carcinoma (SCLC) as well as the effect of LMM on survival, any correlation between the location of the LMM and survival, and a possible increased risk of LMM among patients with brain metastases (BM) located in the posterior fossa.

Between 1980-2003, 458 consecutive patients with SCLC were enrolled in the current study. Patients underwent regular neurologic examination and imaging of the brain before, during, and after treatment. The diagnosis of LMM was established by either the presence of malignant cells in the cerebrospinal fluid or positive clinical symptoms and signs supported by radiologic findings on magnetic resonance imaging.

The group of patients in the current study had a 2% prevalence of LMM and the 2-year cumulative incidence of LMM was found to be 10%. The median survival after the diagnosis of LMM was reported to be 1.3 months. The median survival among patients with LMM located in the spinal cord was 2.4 months. The reported LMM-free survival 2 years after the diagnosis of SCLC was 78% for patients without BM and 61% for those patients with BM. Approximately 15% of the patients with BM located in the posterior fossa developed LMM, whereas only 10% of patients with cerebral BM did.

The current prospective study found a 2-year cumulative incidence of LMM of 10%, with a prevalence of 2%. Patients with LMM located in the spinal cord appeared to survive longer than patients with cranial LMM. SCLC patients with BM located in the posterior fossa may be at a higher risk of developing LMM compared with patients with cerebral BM.