Refining M1 stage in medulloblastoma: criteria for cerebrospinal fluid cytology and implications for improved risk stratification from the HIT-2000 trial

BACKGROUND

Medulloblastoma is the most common malignant paediatric brain tumour, and cerebrospinal fluid (CSF) dissemination (M1 stage) is a high-risk prognostic factor. Criteria for CSF evaluation and for differentiating M0 from M1 stage are not clearly defined, and the prognostic significance of M1 stage in this context is unknown.

PATIENTS AND METHODS

CSF investigations from 405 patients with medulloblastoma of the prospective multicenter trial HIT-2000 (HIirnTumor-2000) were reviewed. Data from 213 patients aged ≥4 years were related to 5-year progression-free (5y-PFS) and overall survival.

RESULTS

Patients with cytological tumour dissemination only (M1 stage only) aged ≥4 years (n = 18) and patients with radiologically detected metastases (M2/3, n = 85) showed a worse 5y-PFS than M0 patients (n = 110) without signs of metastatic disease (5y-PFS 61.1% and 59.6% vs 80.7%; p < 0.02 and p < 0.01, log rank). Patients with positive samples drawn early after surgery who turned negative within 14 days postoperatively (n = 9) and patients with atypical cells (n = 6) showed a 5y-PFS similar to M0 patients. No tumour cells were detected in samples containing <10 nucleated cells. Analysis of cytological criteria showed a better predictive value for tumour cell clusters than ≥2 individual tumour cells.

CONCLUSION

Based on our results, we suggest that CSF medulloblastoma staging should be performed 14 days postoperatively by lumbar puncture, and specimens should contain at least 10 nucleated cells. Cytological tumour dissemination alone (M1 stage only) appears a high-risk prognostic factor associated with an outcome comparable to M2/M3 stage. Tumour cell clusters seem to have a greater impact on prognosis than single tumour cells. This should be validated further.

PATH-07. QUALITY ASSURANCE IN CEREBROSPINAL FLUID CYTOLOGY ASSESSMENT FOR MEDULLOBLASTOMA STAGING LEADS TO POTENTIAL IMPROVED RISK-GROUP ASSESSMENT IN THE PROSPECTIVE MULTICENTER HIT-2000 TRIAL

BACKGROUND

Cerebrospinal fluid (CSF) dissemination of medulloblastoma (M1 stage) is a high-risk prognostic factor. However, because diagnostic criteria for M1 staging are missing we specified process-related and cytomorphological parameters influencing the predictive value of the CSF status.

PATIENTS AND METHODS

CSF samples and cytology reports from 405 medulloblastoma patients of the prospective multicenter trial HIT-2000 were reviewed and related to 5-year progression free survival (5y-PFS).

RESULTS

Tumor cells were detected in 237/1073 CSF cytospins. M1-patients and M2/3 patients with radiologically detected metastases showed a worse 5y-PFS than M0 patients (54% and 52% vs. 76%; p=0.01 and p&lt;0.001). Lumbar sampling was more sensitive than ventricular sampling. M0 diagnosed specimens containing &gt;50% lytic cells and/or less than 10 nucleated cells showed a decreased 5y-PFS (61%). Further investigation of cytological parameters revealed a poor outcome for cases harboring &gt; 3 tumor cell clusters and individual tumor cells (5y-PFS 33%) vs. cases with ≥ 2 individual tumor cells but no clusters (5y-PFS 61%). In bi-variable Cox-regression, ≥ 2 vs. 0 or 1 tumor cells were associated with a Hazard Ratio (HR) of 0.52 (95%-Confidence Interval (CI): 0.12, 2.30; p=0.39), whereas &gt; 3 vs. no tumor cell clusters were associated with a HR of 8.94 (95%-CI: 1.66, 48.22; p=0.01).

CONCLUSIONS

CSF staging in medulloblastoma should comprise lumbar specimens with &lt;50% lytic cells and a minimum of 10 nucleated cells. The predictive value of CSF cytology in M1 cases may predominantly depend on tumor cell clusters. The latter finding needs to be confirmed in prospective trials.