Potential role of ventricular tumor markers in CNS germ cell tumors

There is increasing reliance on oncoprotein assays such as the β-subunit of human chorionic gonadotropin (β-hCG) and alpha-fetoprotein (AFP) for diagnosis or confirmation of histology of central nervous system (CNS) germ cell tumors (GCT), but the relative diagnostic sensitivity and reliability of assays from serum (S), lumbar (L), and ventricular (V) cerebrospinal fluid (CSF) are uncertain.

A total of 86 patients with CNS GCT were identified from our database. Fourteen patients had contemporaneous β-hCG and/or AFP measurements from serum, ventricular, and lumbar CSF at diagnosis (n = 13) or relapse (n = 1), constituting the subjects for this report. Their primary tumor sites were: pineal (n = 8), suprasellar (n = 1), or both (n = 5). Their mean age at diagnosis was 16.0 years (range 9.1-25.9). The male:female sex ratio was 13:1.

For the germinoma-treated patients (n = 8), the median (range) β-hCG values (S, V, L) were 0 (0-6.9), 7.0 (0-57.4), 8.3 (0-34.0) mIU/ml. For patients managed as mixed malignant GCT (MMGCT) (n = 6), the median (range) β-hCG values (S, V, L) were 3.9 (0-58.0), 3.6 (0-147.0), 61.8 (0-358.0) mIU/ml. The median (range) AFP values were 7.5 (0-27,400.0), 2.0 (0-2,981.0), 3.0 (0-14,015.0) ng/ml. Lumbar CSF β-hCG values were equal or greater than those in ventricular CSF or serum in 12 of 13 cases (92.3%). All patients with MMGCT had lumbar AFP equal or greater than the ventricular CSF values, while serum AFP values remained highest.

Ventricular CSF values cannot be considered a replacement for lumbar CSF. Lumbar CSF is the most reliable source of tumor markers to establish baseline and follow-up diagnostic endpoints.