PROLIFERATIVE CHARACTERISTICS OF JUVENILE PILOCYTIC ASTROCYTOMAS DETERMINED BY BROMODEOXYURIDINE LABELING

BROMODEOXYURIDINE (BUdR) LABELING studies were performed to characterize the biological and clinical behavior of 50 juvenile pilocytic astrocytomas (JPAs) from 47 patients. Each patient received an I.V. infusion of BUdR before tumor resection; the excised tumor specimens were stained by the immunoperoxidase method with anti-BUdR monoclonal antibody to determine the BUdR labeling index (LI), or percentage of S-phase cells. The BUdR LI ranged from 0.22 to 4.3% (< 1% in 34 and greater-than-or-equal-to 1% in 16; mean +/- SE, 1.05 +/- 0.13%). Tumors from younger patients often had higher LIs, but as the age of the patients increased, the frequency of tumors with LIs greater-than-or-equal-to 1% decreased. Tumors from male patients had higher LIs than those from female patients (1.36 +/- 0.20% [SE] vs. 0.75 +/- 0.13%; P < 0.01), and tumors in the cerebellum had higher LIs than those in the hypothalamus (1.39 +/- 0.24% vs. 0.87 +/- 0.15%; P < 0.05). The LI did not correlate with the gross appearance of the tumor (solid or cystic) or with outcome after the initial diagnosis. Overall, there was no difference in the LIs of primary and recurrent tumors. Four tumors (3 primary and 1 recurrent) that recurred after subtotal resection had a higher mean LI than 32 tumors that did not recur after subtotal resection (2.6 +/- 0.7% vs. 0.74 +/- 0.09%; P < 0.005). None of 14 totally resected tumors (mean LI, 1.3 +/- 0.2%) has recurred. Our results suggest that most JPAs grow slowly, as reflected by their low BUdR LIs, but some JPAs have high LIs, which indicate a high proliferative potential. Some JPAs with high LIs recurred, but, in most cases, the clinical course was excellent regardless of the LI. These observations suggest that the growth rate of JPAs is programmed to change. Tumor growth appears to slow down (but may not cease) by the time the patient reaches about 20 years of age. Therefore, if the mass effect is controlled until the growth rate slows, the clinical course may be favorable and follow-up at a longer interval may be possible. Treatments that have long-term side effects, such as radiation therapy, should be avoided until other treatment options have been exhausted.