gms | German Medical Science

Objective: Sporadic pilocytic astrocytomas (PA) WHO grade I are rare CNS neoplasms occurring mainly during the 1^st two decades of live with a preference of infratentorial location. In paediatric patients, BRAF V600E mutations and BRAF/KIAA1549 gene fusions are frequent molecular events, and complete resection (CR) has been shown to be curative. However, due to the even lower incidence, little is known about the clinical course and the molecular characteristics of PA in adults.

Method: 36 patients 17 years and older treated for PA at our department between 1996 and 2014 were retrospectively identified. Demographic, treatment, neuroimaging, and survival data and the presence of molecular markers were collected from our institutional database and from medical records. Patients with a follow-up (FU) over 24 months (n=22) were included in the survival analysis employing log-rank tests. Fisher’s exact test was used for comparisons of proportions.

Results: This single-centre study analysed 36 adult patients with a median age of 28.5 years (range 17-66 years) and a median follow-up of 34.5 months (range 0-205 months). Supra- (47%) and infratentorial (53%) location was evenly distributed and was not age-dependent (p=0.74). Radiographically confirmed CR was achieved in 23 patients (64%), making use of intraoperative MRI (iMRI) in 12 cases with additional resection in 7 cases. The extent of resection (EOR) was not location-dependent (p=0.3) but trended to impact on the frequency of tumour relapse, with 2 relapses occurring after complete and 6 relapses after partial resection (p=0.07). A second relapse was observed in 4 cases, even in 1 patient with two previous CR. Non-surgical treatment intensity was low. Median progression-free survival (PFS) was 27.5 months (range 0-135 months). There was 1 tumour-related death. Molecular markers were available in a minority of tumours, but presence of BRAF V600E (1/13 cases) and BRAF/KIAA1549 (3/10 cases) was rare. In patients with a FU over 24 months, PFS was non-significantly prolonged after CR (135 vs. 46 months; p=0.18).

Conclusions: Adult PA patients follow a more aggressive clinical course compared with paediatric patients as tumour relapse occurred in 36% of cases; even after CR. Tumour location was not predictive of patient outcome. IMRI helped to maximize the EOR, which in turn showed a trend for a prolonged PFS and a lower frequency of tumour relapse and stresses the importance of maximum safe resection also in adult PA patients.