[en] Purpose: 582 consecutive cases of primary intracranial meningioma undergoing resection at the Mayo Clinic, (Rochester, MN) were reviewed to determine overall survival (OS), progression free survival(PFS), prognostic factors predicting recurrence, and to determine the importance of radiation therapy in the management of this tumor. Materials and Methods: Between 1978-1988, 582 cases of primarily resected meningiomas were identified based on the tumor and operative registries where diagnosis was between 1978-1988 inclusive. PFS was identified by radiographic progression. Follow-up was accomplished by chart review, and a detailed questionnaire sent to patients and referring physicians. Estimation of OS and PFS distributions were done by the Kaplan-Meier method. The log rank test was used to assess which factors were associated with PFS. Proportional hazard modeling was performed to obtain a subset of independent predictors of PFS. Results: the median age was 57(5-93). 67% were female. CT identified the tumor in 91% of cases. There was associated edema in 21% and 2% were radiographically en plaque. There were 17 patients with multiple tumors, four of whom had a known diagnosis of neurofibromatosis. Gross total resection (GTR) was accomplished in 80%, radical subtotal or subtotal resection(STR) in 20%, and biopsy in <1%. Peri-operative mortality was 1.4% and 3.2%, 10 days or 90 days from surgery, respectively. OS was significantly, but minimally, decreased from that of an age, sex matched control cohort population. PFS at 5 and 10 years was 85% and 75% with GTR, 75% and 35% for STR, respectively. Factors predicting recurrence at 7.5yrs were on univariate analysis: younger age, location (anterior visual pathway including orbit), STR, surgical findings of en plaque tumor, soft tissue invasion, and dural sinus invasion. Pathologic factors associated with a decrease in PFS were: brain invasion(small subset), tumor sheeting, tumor necrosis, increased (>53) cellularity, and four or more mitoses per 10 HPF. Multivariate analysis indicated young age, male sex, en plaque at surgery, were significant for decreased PFS when only patient characteristics were considered. When treatment and pathologic factors were also considered, then young age, male sex, less than GTR, and tumor sheeting were predictors for decreased PFS. 10 patients had RT after initial resection, two of whom recurred. There were 107 first recurrences. 50 were observed(no intervention within 3 months), 35 treated by surgery alone, 11 had S+RT, and 11 were treated with RT alone. Considering those patients treated at recurrence (n=57), PFS was at 2 and 5 years was 64% and 59% with S alone, 83% and 83% with S+RT or RT alone, (p<0.001). At first recurrence, of the 22 patients treated with RT (19 EBRT, 3 Gamma Unit RT), four ultimately recurred. Including previous RT failures, there were 20 second recurrences. 10 second recurrences were managed with S alone, 4 with S+RT, and 6 with RT alone. Two patients treated with RT+-S at second recurrence recurred (3rd recurrence). RT doses were: adj. RT (4900-5760cGy), mean 5220cGy, first rec. RT (3000-6480cGy) mean 5400cGy with only one pt. dose <4500cGy, second recurrence RT (3060-6006cGy) mean 5076cGy, with two pts. treated <4500 cGy. There were two radiation therapy complications in 42 patients. No dose response was observed. Conclusions: Surgery can be accomplished with excellent results and minimal mortality. Surgery alone was associated with a 10 year radiographic recurrence rate of 25% (GTR), and 65%(STR) stressing the need for long-term follow-up. Prognostic factors predicting radiographic recurrence have been determined. Symptomatic patients at recurrence may benefit from the use of radiation therapy with or without surgical resection