Pilocytic astrocytoma: a retrospective review

Purpose: The principle objective of this study is to determine the role of radiation therapy in the management of pilocytic astrocytoma. The specific aims are to assess the results of surgical resection +/- radiation therapy, the dose-response relationships for local tumor control, and the prognostic indicators. Materials and methods: Between Jan. 1970 and Dec. 1995, 60 patients with pilocytic astrocytomas (27 cerebellum, 23 hypothalmus/brain stem, 4 temporal, 3 frontal, and 3 occipital) were seen. All pathologic slides were reviewed and confirmed. Of these, 30 patients had surgery only (8 subtotal resections and 22 total resections), 8 had biopsy followed by radiotherapy (6) or chemotherapy (2), 21 had surgery and postoperative radiotherapy (20 subtotal resections and 1 total resection) and 1 was observed only. The radiation dose was 40.6 Gy/31fr/44ds to 60.2 Gy/35fr/49ds (mean = 52.1 Gy). Results: The overall 5- and 10-year actuarial survival rate was 93% and 93%, and the relapse-free survival rate was 86% and 80%, respectively. Eight patients developed local recurrence and one had leptomeningeal spread. Two patients receiving chemotherapy (vincristine + carboplatin) had persistent but stable disease. The one patient who was observed eventually required surgical resection 25 months later. Subtotal resection without RT: The local recurrence rate was 38% ((3(8))) if no RT was given after subtotal resection. Only 2 of the 3 recurrences were salvaged. All 22 patients who had tumor totally resected had local tumor control. Subtotal resection/biopsy only plus RT: Radiation therapy was effective in controlling the gross disease in 75% ((15(20))) of patients with subtotal resection, and 100% ((6(6))) of patients with biopsy only. In 14 patients receiving a tumor dose ≥ 51 Gy, 13 (93%) had local control, in comparison, to (11(15)) (73%) receiving a tumor dose <51 Gy had tumor control. Location of tumor: Sixty-three percent ((17(27))) of patients with tumor in cerebellum had tumor totally resected whereas none of 23 patients with tumor in the hypothalmus/brain stem did. Similarly, the local control rate was 93% in cerebellar tumors, compared with 60% in hypothalmus/brain stem. Conclusion: 1) Radiation therapy should be employed if the tumor is incompletely resected or the tumor was biopsied only. 2) A dose of 51-55 Gy appears to be adequate to control the majority (93%) of the tumors. 3) Radiation therapy is not needed if tumor is totally removed. 4) Location of tumor is prognostically related, with the best prognosis in cerebellum and the worst in hypothalamic region