gms | German Medical Science

Objective: Gliomas, the most common human brain tumors, were divided by the WHO according to their malignancy grade, but in the majority of studies no differentiation between grade III and IV gliomas occurs. Our group has access to a large number of grade III gliomas to investigate this tumor grade in particular.

Methods: In total, we examined 37 patients with grade III gliomas, and 9 precursor lesions and recurrences, respectively. We performed two-color fluorescence-in situ hybridization on cryostat tumor tissues with centromere-specific probes for chromosome 7 and 10 and locus specific probes for 1p36 and the telomere-region of 19q. The results were compared with the histopathological diagnosis and the patients’ progression-free and overall survival time.

Results: Almost all grade III astrocytomas (10/11) showed gains of chromosome 7 and losses of chromosome 10. Deletions of 1p36 were observed in half of the cases (6/11), and all tumors showed deletions of 19q (11/11). Oligoastrocytomas showed gains of chromosome 7 (12/14) and losses of chromosome 10 (13/14) in nearly all cases. Furthermore, 6/14 cases showed deletions of 1p36, and in all cases (14/14) deletions of 19q were detected.

Surprisingly, pure oligodendrogliomas also showed a very high proportion of cases with gains of chromosome 7 (11/12) and losses of chromosome 10 (12/12) besides their typical deletions of 1p36 (9/12) and 19q (12/12).

Statistical analyses revealed no correlation between tumor entity, genetic alterations and prognosis. However, Kaplan Meier analysis showed a tendency for a better prognosis in oligodendrogliomas, compared with oligoastrocytomas and astrocytomas.

Conclusions: Interestingly, our study revealed a clear evidence of an important role of all investigated chromosomal regions in these three different anaplastic tumor types. Even if we observed a trend for better survival of pure oligodendroglial tumors, no correlation with the genetic alterations were detectable in our group of patients.