Clinical efficacy of tumor-treating fields for newly diagnosed glioblastoma.
2046 Background: Recent clinical trials have shown that adding tumor treating fields (TTF) to the Stupp protocol (SP) has increased survival after glioblastoma (GBM) diagnosis. However, whether this regimen improves population-based survival for patients with GBM remains unknown. Methods: We retrospectively identified adult patients with newly diagnosed GBM treated at our institution from January 2000 to July 2017 (n = 438, median age: 63 years).We grouped patients into three time periods for comparison: 2000-2004 (group 1, prior to SP), 2005-2013 (group 2, SP) and 2014-2017 (group 3, adding TTF to SP). The Kaplan-Meier method was used to estimate survival. Statistical analysis included unadjusted group comparisons by Chi-square and Log-rank tests and adjusted group comparisons using logistic and Cox models. Results: Thirty-seven percent (43/117) of patients with GBM in group 3 received TTF with SP therapy; when compared to those who received SP only, these patients had significant improvements in 6-month and 1-year overall survival (OS) rates (100.0% vs. 82.4%, p < 0.01; 86.0% vs. 66.2%, p < 0.05, respectively) (unadjusted for prognostic factors including sex, age, KPS and extent of resection) and an increased trend of median OS (479.0 vs. 448 days, p = 0.269). However, after adjusting for those prognostic factors, we didn’t find a statistically better survival for patients treated with TTF (OR: 6.156, p = 0.097, OR: 2.102, p = 0.185, respectively). Furthermore, multivariate Cox proportion hazards model after adjusting for those prognostic factors showed no significant survival benefits for patients treated with TTF and SP compared to those treated with SP only (HR = 0.797, p = 0.648). In addition, we didn’t find significant increases of 6-month, 1-year survival rates and median OS for patients in group 3 when compared to those in group 2 who had seen increased trends of survival trends when compared to those in group 1. Conclusions: Although adding TTF to SP appeared to benefit patients with GBM, this effect might be due to selection bias, e.g., TTF was offered to those patients with better prognostic factors. Ascertaining the long-term benefits of TTF requires further investigation.