Univariate and multivariate statistical analysis of high-grade gliomas: The relationship of radiation dose and other prognostic factors

Univariate and multivariate statistical analyses were used to examine the relationships between duration of survival and multiple variables in the presentation and treatment of 82 patients with high-grade gliomas (16 grade 3, 66 grade 4). The median survival time of the eight patients who received ⩽40 Gy to the tumor bed was 16 weeks and was 17 weeks for the three who received between 40 and 50 Gy. Patients who received 50–60 Gy had a median survival time of 62 weeks, compared to 54 weeks in patients who received 60–70 Gy. These differences in median survival time were statistically significant between the extremes ( p = 0.0001), as well as between the 40–50 Gy group and the 50–60 Gy group ( p = 0.02). However, no significant difference could be detected between the groups receiving 50–60 Gy versus 60–70 Gy. Univariate analysis also identified preoperative performance status, age, histologic grade, extent of surgery, and seizure history as prognostic factors. Cox multivariate analysis was performed to identify variables that were significant in independently predicting duration of survival. Although contemporary studies have shown many variables to be significant in predicting survival, our analysis found that many of them were not independently predictors. The variables which indenpently predicted improved duration of survival were greater total radiation dose to the tumor bed ( p < 0.0001), superior preoperative performance status ( p = 0.003), and grade 3 versus grade 4 ( p = 0.04). Younger age at diagnosis was marginally significant ( p = 0.07). In the group of 60 patients receiving >50 Gy, a discriminant analysis was also performed. The patients were divided into two groups based on apparent clusters of survival times: ⩾60 weeks versus 60 Gy.