Cerebellar pilocytic astrocytoma case series

A institutional database was screened for patients with PA treated between 2000 and 2019. Patients ≤ 18 years of age with complete clinical records, preoperative contrast enhanced magnetic resonance imaging (MRI) and postoperative follow-up time of ≥ 6 months were suitable for study inclusion. Functional outcome was quantified with the modified Ranking Scale (mRS) score and assessed at admission, at discharge and at every follow-up investigation. Predictors of hydrocephalus, cranial nerve deficits and tumor recurrence were evaluated.

A total of 57 pediatric patients with a mean age of 7.7 ± 4.8 years were included in the analysis. 27 (47.3%) children suffered from hydrocephalus at diagnosis, out of which 19 (33.3%) required a subsequent VP-Shunt. 22 (39.3%) patients had a partial resection, of which 9 (40.9%) went through second-look surgery. 2 patients with initially radiological confirmation of complete resection, had a tumor recurrence at FU and needed second-look surgery. Among the children requiring second-look surgery, 7 (63.6%) had a complete resection. Favorable outcome (mRS≤2) after initial and second-look surgery was observed in 52 patients (91.2%). Univariate analysis identified tumor location in the floor of the 4th ventricle (p = 0.030), and repeated surgery for tumor remnant removal (p = 0.043) as predictors for post-operative cranial nerve deficits. Multivariate analysis confirmed this independent association. The incidence of tumor recurrence occurred more often in patients with previous partial resection (p = 0.009) as well as in lesions located in the cerebellar peduncles (p = 0.043). Partial resection remained an independent predictor after multivariate logistic regression analysis (p = 0.045).

Incomplete resection of posterior fossa PA is a risk factor for tumor recurrence and repeated surgery to remove tumor remnants increases the risk of new postoperative deficits. Thus, the risk of iatrogenic deterioration due to second look surgery should be implemented in the primary pre- and intraoperative decision-making ¹⁾.

In a retrospective study of 73 patients operated on for cerebellar pilocytic astrocytomas, results of treatment, outcome and biological behaviour of residual tumour were analysed. Complete tumour resection proven by CT or MRI scans within 1 year after surgery was achieved only in 69% of cases. In 31% of cases the surgeon's opinion on the extent of surgical resection was not borne out by the result of postoperative neuroimaging. Progression of residual tumour or tumour recurrence appeared in 19% of patients. 1 patient showed metastatic spread along the craniospinal axis, and in 1 patient malignant degeneration appeared during follow-up. Stable residual tumour or regression of residual tumour was seen in 14% of patients. Outcome after surgical treatment, which was combined with irradiation in 10 patients (14%), was favourable in 80% and unfavourable in 20% of patients. This outcome of treatment was not influenced by a second operation for progression of residual tumour or recurrent tumour. Characteristics of patients with tumour progression after the first operation did not differ from those of the whole group. There were 17 reoperations for residual or recurrent tumour, 10 of which took place within 4 years after the initial surgical treatment. Surgery-related morbidity was 15% and mortality 4%. Irradiation to residual tumour in 8 patients was followed by complete regression in 1 patient, progression in 4 patients and no changes in 1 patient. For the remaining 2 patients the effect of irradiation on the residual tumour is unknown. Factors that determine the prognosis are discussed on the basis of this retrospective analysis and the data from the literature. It is concluded that optimal treatment for a cerebellar pilocytic astrocytoma does not consist solely in surgery with the aim of total tumour removal and careful tumour handling in order to avoid spread of tumour cells and subsequent metastases and additional radiation therapy is strictly selected cases, but also in posttreatment follow-up based on direct postoperative neuroimaging, preferably by MRI. An algorithm for postoperative follow-up management is presented ²⁾.