Main Session
Sep
27
PQA 01 - Gastrointestinal Cancer and Central Nervous System
Presenter(s)
Neil Mookerjee, MD - Thomas Jefferson University, Philadelphia, PA
N. Mookerjee1, I. Alnahhas2, N. Martinez3, J. Glass3, K. Sarmiento4, T. Zhan5, and W. Shi4; 1Department of Radiation Oncology, Thomas Jefferson University Hospital, Philadelphia, PA, 2Department of Radiation Oncology, Thomas Jefferson University, Philadelphia, PA, 3Dept of Neurosurgery, Thomas Jefferson University Hospital, Philadelphia, PA, 4Department of Radiation Oncology, Sidney Kimmel Medical College & Cancer Center at Thomas Jefferson University, Philadelphia, PA, 5Dept of Pharmacology and Experimental Therapeutics, Thomas Jefferson University, Philadelphia, PA
Purpose/Objective(s):
Tumor Treating Fields (TTFields) added to standard temozolomide therapy improve progression-free survival (PFS) and overall survival (OS) in patients with newly diagnosed glioblastoma (ndGBM). Higher TTFields compliance has been associated with improved PFS and OS. It remains unclear whether percent compliance alone or cumulative exposure more accurately predicts benefit. We hypothesized that cumulative TTFields exposure would demonstrate a stronger association with OS and PFS than compliance percentage alone.Materials/Methods:
This is a single institution retrospective review of adult patients with ndGBM who received TTFields treatment. Inclusion criteria included =1 month of TTFields use and Karnofsky Performance Status =60 at diagnosis. Demographic, clinical, and TTFields treatment variables were obtained from electronic medical records and the TTFields device database. Exposure variables included duration of TTFields use, compliance, and a cumulative exposure metric defined as the number of months on TTFields therapy multiplied by the percent compliance. OS and PFS were evaluated using multivariable Cox proportional hazards models adjusted for age at surgery, gross total resection, MGMT methylation status, and sex.Results:
A total of 106 patients were included in this study. The median age at surgery was 59.6 years, 50% had gross total resection, and 37% had MGMT methylation. The median TTFields duration was 8.1 months, and the median compliance was 59%. Longer TTFields duration was associated with improved OS (HR 0.96, 95% CI 0.93–0.98; P<.001) and PFS (HR 0.95, 95% CI 0.93–0.97; P<.001). Each additional month of therapy reduces the hazard of death (HR 0.96) and progression of disease (HR 0.95). Compliance percentage alone was not associated with OS or PFS after adjustment. Cumulative exposure was associated with improved OS (HR 0.94; P<.001) and PFS (HR 0.93; P<.001). Gross total resection was associated with improved PFS (HR 0.61; P=.024). MGMT methylation was protective for OS (HR 0.56; P=.018) and PFS (HR 0.47; P=.002). Increasing age was associated with worse outcomes (OS HR 1.02; P=.019; PFS HR 1.03; P=.002).Conclusion:
This study showed that TTFields treatment duration and cumulative exposure were independently associated with improved OS and PFS. Compliance percentage alone was not independently predictive. These findings suggest that cumulative exposure may better reflect clinical benefit than compliance percentage alone. Further investigation incorporating time-dependent modeling may help account for differences in treatment duration driven by survival and underlying tumor biology.