Cerebrospinal fluid gastrin releasing peptide in the diagnosis of leptomeningeal metastases from small cell carcinoma

BACKGROUND, The clinical diagnosis of leptomeningeal metastases is often di fficult to substantiate. Patients with an underlying malignancy typically p resent with neurologic symptoms referable to multiple levels of the neuraxi s. Although most patients have an abnormal cerebrospinal fluid (CSF), less than 60% have evidence of malignant cells on cytologic examination from a s ingle lumbar puncture, and the disease is usually advanced in patients with positive results. An elevated serum level of gastrin releasing peptide (GR P) in patients with small cell carcinoma has emerged as one of the most use ful markers for disease activity. METHODS. A patient with small cell carcinoma presented with signs of mening itis and an abnormal CSF. However, the CSF gave repeatedly negative cytolog ic results. Hence, serum and CSF were analyzed for GRP. RESULTS. The CSF GRP level was elevated by more than six orders of magnitud e above the serum level. An autopsy demonstrated extensive meningeal and pa renchymal brain involvement by small cell carcinoma. CONCLUSIONS. The diagnosis of leptomeningeal metatases in patients with sma ll cell carcinoma can be established by CSF GRP testing, even when cytologi c examination is negative. Cancer 2001;91:2122-6. (C) 2001 American Cancer Society.