The effect of the time interval between temozolomide and radiotherapy in adjuvant high-grade glioma treatment

Abstract

Purpose/Objective(s) The standard of care for high grade glioma (HGG) treatment consists of postoperative radiotherapy and temozolamide (TMZ). The effect of time between TMZ administration and RT on treatment outcomes is not well defined. The purpose of this study was to examine the interval between oral administration of TMZ and RT, and its effect on treatment outcomes in patients with HGG. Materials/Methods The clinical data of 277 patients with HGG treated between 2009 – 2021 at four centers were retrospectively analyzed. The following are the inclusion criteria: Pathologically proven grade ≥3 glial tumors, ≥18 years old, and completion of curative RT with concurrent oral 75 mg/m2/day TMZ. Patients who were unable to take oral TMZ, or had previously been treated with TMZ and/or RT were excluded. The TMZ to RT interval (TRI) was calculated from the time of oral TMZ administration to the time of RT fraction. In relation to the TMZ half-life, the interval time was divided into <2 h and ≥2 h groups. Progression free survival (PFS) is calculated as the time between the end of RT and clinical or radiological progression. Overall survival (OS) is calculated from the time of diagnosis to the last follow-up. Results The median age was 58 years (range: 19–81). 159 patients (57.4%) were male, while 118 (42.6%) were female. 75.4% of patients had an ECOG performance score (ECOG PS) of 0–1, and 54.5% had gross total resection (GTR). The median fraction and total RT doses were 2 Gy (1.8–3) and 60 Gy (40–60), respectively. The median follow-up was 15.2 months (range: 1.9–75.1) for the entire cohort. Two-year OS and PFS rates were 35% and 15%, respectively. After completion of RT, disease progression occurred in 255 patients (92.1%) at a median of 6.4 months (range, 0.2–64.9). The 2-year OS was 42.8% for patients with a TRI >2 hours and 32% for patients with a time interval of ≤2 hours (p = 0.18). Similarly, there was no statistically significant difference in 2-year PFS between the two groups (12.8% vs. 9%; p = 0.95). Age, ECOG PS, and type of surgery were all significant prognostic factors for OS and PFS in univariate analysis. In multivariate analysis, advanced age [HR = 1.03 (95% CI, 1.01 – 1.04); p<0.001], poor ECOG PS [HR = 2.14 (95% CI, 1.56 – 2.94); p<0.001], and incomplete surgical resection [HR = 1.39 (95% CI, 1.06–1.84); p = 0.02] were independent predictors of poorer OS. Similarly, age [HR = 1.02 (95% CI, 1.01 – 1.03); p = 0.002], ECOG PS [HR = 1.57 (95% CI, 1.17 – 2.09); p = 0.002], and type of surgery [HR = 1.41 (95% CI, 1.10 – 1.80); p = 0.006] were all significant prognostic factors for PFS in multivariate analysis. Conclusion We found that advanced age, poor performance status, and incomplete surgical resection were all predictive of poor OS and PFS in this current study. However, we were unable to detect a statistically significant effect of the time interval between oral administration of TMZ and RT. Validation of our findings will require a longer follow-up period and randomized trials.