P17.10 * GEMISTOCYTIC ASTROCYTOMAS: MONO-INSTITUTIONAL EXPERIENCE

Abstract

Gemistocytic astrocytoma (GA) is variant of diffuse astrocytoma, characterized by the presence of at least 20% gemistocytic neoplastic astrocytes (usually around 35%, in the past 60%). They represent 9-19% of astrocytic tumors with median age at diagnosis of 40 years. Population-based studies on low grade gliomas suggest a worse prognosis for GA compared to fibrillary or protoplasmatic variants. WHO classification does not qualify GA as a high grade astrocytoma, since there is insufficient data to define gemistocytic morphology as an independent prognostic indicator. The mOS reported is 2.5 years, with a 5-year survival rate of 30%. In the present study we retrospectively identified all consecutive patients with proven gemistocytic astrocytoma diagnosed and treated in our Institution between 1985 and 2012 with the aim to correlate the clinical and histopathological findings with survival. Primary endpoint was OS in the whole group of patients and secondary endpoint was OS correlated to age and presence of anaplasia. A total of 78 patients (28 female, and 58 male), with median age at diagnosis 46 years, underwent surgical procedure at diagnosis (42% second surgery and 8% third surgery). In 32% (25/78 patients) of patients focal signs of anaplasia were described at diagnosis. 63% (49/78) underwent postoperative radiotherapy and 70.5% (55/78) underwent chemotherapy at different time points and with different schedules and drugs (nitrosureas, PCV, fotemustine, temozolomide). Median OS (in 78 patients) was 54 months (range 3-327 months). 26 patients were alive at the end of 2012. The mOS in 53 patients without anaplasia was 86 months (p 0,7 95%CI), mOS in 25 patients with anaplasia was 51 months (p 0,7 95%CI), mOS in 51 patients < 50 years was 86 months (p 0,27 95% CI), mOS in 27 patients ≥ 50 years was 42 months (p 0,27 95%CI). Despite several limitations of the study, our data show a median OS similar to other studies, with a better prognosis in patients younger than 50 years and in patients without focal anaplasia at diagnosis (data not statistically significant). Gemistocytic astrocytoma still continues to be enigmatic both in terms of definition and prognostic implications. Whether these tumors should be considered high grade astrocytomas remains open. Future prospective studies should clarify the value of gemistocytic morphology as an independent prognostic factor, and should investigate the molecular mechanisms that promote the formation of gemistocytes.