Purpose: To quantify CSF levels of polysialic-neural cell adhesion molecule (PSA-NCAM) in patients with medulloblastoma (MB) metastasis, to assess the correlation with other diagnostic techniques (imaging and cytology) and clinical features, and to determine whether it is a suitable marker to monitor response to treatment and subsequent follow-up data.
Patients and methods: PSA-NCAM levels were measured using a double-site enzyme-linked immunoadsorbant assay (ELISA) in 145 samples from 14 controls and 29 patients with MB. Clinical status of patients, imaging, and cytologic data were available at the time of each lumbar puncture. Medians and ranges for the 131 pooled PSA-NCAM concentrations were calculated for the MB versus the control groups, and for MB patients for normal versus abnormal groups at cytology or imaging, and for four clinical subgroups, respectively. For patients with MB, three PSA-NCAM measurements that corresponded to punctures performed during three time periods following surgery were selected. The kappa measure of agreement was calculated between normal and abnormal groups at cytology or imaging, and between groups of patients in remission and refractory, respectively. For the same phases, sensitivity and specificity of PSA-NCAM and cytology tests and their 95% confidence intervals (95% CIs) were computed.
Results: PSA-NCAM was never detected in control CSF. PSA-NCAM concentration medians were higher in CSF with metastatic cells or that corresponded to abnormal imaging than in the corresponding normal groups (P < .05). The PSA-NCAM concentration median was significantly higher (P < .05) in CSF from patients refractory to treatment or who relapsed than from patients in remission. Agreements between PSA-NCAM and clinical status and between PSA-NCAM and cytology were excellent during and after treatment. The sensitivity of PSA-NCAM test was always better than that of cytology, whereas its specificity was lower for phases that corresponded to more than 1 month following surgery. However, specificity was 100% for patients refractory to treatment or with relapse.
Conclusion: PSA-NCAM measurement appears to be a new biologic marker of possible use in the management of patients with MB.