RECURRENCE PATTERNS AND ANAPLASTIC CHANGE IN A LONG-TERM STUDY OF PILOCYTIC ASTROCYTOMAS

Thirty-six cases of pilocytic astrocytomas treated at the Childrens Ho spital of Los Angeles from 1984 through 1995 were reviewed. The mean a ge at initial presentation was 8 years (range 15 months to 14 years). These patients were followed for an average of 5.5 years. No patient w as given chemotherapy or radiation therapy after the initial surgery f or pilocytic astrocytoma. Twenty-three patients (64%) had a gross tota l resection with no residual tumor on immediate postoperative imaging studies. Three of these children had tumor recurrences 2-5 years after their initial surgery, requiring re-excision of their tumors. All 3 p atients are subsequently tumor-free, with follow-up ranging from 4 to 10 years. In 4 patients with residual tumor involving the brainstem, t here has been neither imaging evidence of tumor enlargement nor progre ssion of clinical findings at 2.5, 4, 6 and 6 years, respectively. Nin e of the 13 patients with residual tumor underwent re-excision, either for progression of symptoms or documented tumor growth on imaging stu dies. The second operation was undertaken an average of 1 year (range 1 month to 6 years) after the first. In 4 of these children (11% of ou r whole series), the recurrent tumor was classified as anaplastic astr ocytoma. Three of these 4 children received radiation and/or chemother apy, with only 1 patient showing disease progression in the follow-up period. Repeat blinded histopathological examination of these tumors c onfirmed both diagnoses. However, it was noted that 3 of the 4 pilocyt ic astrocytomas which subsequently showed anaplastic change initially displayed increased perivascular cellularity, while only 2 of the rema ining 32 tumors exhibited this feature. These results encourage contin ued vigilance in the follow-up of pilocytic astrocytomas, and describe a histological feature which might indicate a more aggressive disease course.