Comparison of Adult and Pediatric Pilocytic Astrocytomas Using Competing Risk Analysis: A Population-based Study

Background: Pilocytic astrocytoma(PA) is a relatively benign tumor occurring primarily in the pediatric population. Comparison of characteristics and survival of this tumor between adult and pediatric patients in a single, population-based study is yet to be performed.

Objective: We aimed to directly compare the characteristics and survival of pilocytic astrocytoma between pediatric and adult patients in a single, population-based study.

Methods: We utilized the SEER database using data from 1983 to 2016. All patients with histologically confirmed, intracranial pilocytic astrocytoma were included and divided into a pediatric(age<18 years) or adult group. Due to lower risk of tumor-specific-mortality, we utilized a competing risk analysis to account for mortality from other causes. Univariable and multivariable competing risk analysis(CRA) was performed, and sub-distribution hazard ratio(SHR) or adjusted SHR(aSHR) was reported.

Results: A total of 4357 patients comprised the final cohort, with 3014(69.2%) pediatric patients. As compared to the pediatric group, adult patients were predominantly White(p < 0.01), with PA less likely fully resected(p = 0.01), smaller tumor size(p < 0.01), and were less often located in the cerebellum(p < 0.01). Multivariable CRA revealed a worse prognosis for the adult group(p < 0.01), regional or distal extension(p < 0.01), and non-cerebellar locations including frontal(p < 0.01), parietal(p < 0.01), ventricular(p < 0.01) or brainstem(p < 0.01). Improved prognosis was seen with more recent year-of-diagnosis(2003-2016, p = 0.03), gross-total/total resection(p < 0.01), and biopsy only patients(p = 0.02).

Conclusions: Pilocytic astrocytomas in adult patients have a worse prognosis than pediatric patients. Cumulative incidence of cancer-specific-mortality is higher in adults when adjusted for other factors. PAs with regional or distal extension and non-cerebellar locations carry worse outcomes. Surgery remains an effective treatment and GTR/TR should be achieved when possible.