gms | German Medical Science

Objective: Loss of heterozygosity (LOH) 1p/19q has been associated with a better overall prognosis in oligodendroglial tumours. Whether this finding is treatment independent and similarly important for astrocytomas, still remains unclear. This prospective study evaluates 1. the incidence of LOH 1p/19q in oligodendroglial tumours as compared to astrocytoma (WHO II/III), 2. the intratumoural distribution of this marker and 3. the prognostic impact of LOH 1p/19q.

Methods: 111 adult patients with a primary or recurrent oligodendroglial tumour or astrocytoma (62 astrocytoma WHO II, 24 astrocytoma WHO III, 20 oligodendroglial tumours WHO II, 5 oligodendroglial tumours WHO III) were included (03/2003-09/2005). LOH 1p/19q analysis was performed from stereotactic biopsies in 64 (1-5 specimens for LOH analysis were taken from different targets for elucidation of the intratumoural distribution) and open resection in 47 patients. In 69 patients with a WHO II glioma harbouring a favourable prognostic profile, radiotherapy and/or chemotherapy was performed at the time of tumour progression. Prognostic factors were obtained from multivariate analysis and life analysis was done with the Kaplan-Meier method.

Results: Incidence of LOH 1p/19 was significantly higher in tumours with an oligodendroglial component (p<0.001, 64% in oligodendroglial tumors vs. 29% in astrocytoma). Stereotactic biopsy revealed no LOH 1p/19q-heterogeneity within the individual tumours investigated (64 tumours with either histology). Length of survival was significantly longer in oligodendroglial tumours WHO II/III with LOH 1p/19q (p<0.001, 5-year survival-rate 90% vs. 30%). Moreover, in those patients with oligodendroglial tumours undergoing delayed treatment (17 patients), progression free survival was still longer for those with LOH 1p/19q (p<0.001, median progression free survival 60 months vs. 20 months). In contrast, a similarly powerful impact of LOH1p/19q in astrocytic tumours could not be detected (p>0.05). A correlation between LOH1p/19q status and the risk of malignant transformation was not found in either of these low-grade tumour entities.

Conclusions: There was no intratumoural heterogeneity for LOH1p/19q in astrocytoma and oligodendroglial tumors. Oligodendroglial tumours (WHO II or III) should be regarded as a distinct tumour entity. The prognostic impact of this marker seems to be al least in part treatment-independent in these tumours. The role of LOH1p/19q in pure astrocytoma is far less important.