Main Session
Sep
27
PQA 01 - Gastrointestinal Cancer and Central Nervous System
2216 - Optimization of TTFields Delivery Using Segmentation-Based Treatment Planning with Head-Flexible Arrays
Presenter(s)
Wenyin Shi, MD, PhD - Thomas Jefferson University, Philadelphia, PA
W. Shi1, N. Urman2, N. Shapira2, A. Naveh2, N. Avgeropoulos3, L. Lustgarten3, A. Lipson3, O. Bakalo3, P. Conlon3, and M. T. Ballo4; 1Department of Radiation Oncology, Sidney Kimmel Medical College & Cancer Center at Thomas Jefferson University, Philadelphia, PA, 2Novocure Ltd, Haifa, Israel, 3Novocure Inc, Portsmouth, NH, 4Cleveland Clinic Foundation, Cleveland, OH
Purpose/Objective(s):
TTFields therapy is a physical modality that delivers electric fields to tumors through adhesive arrays placed on the skin. Preclinical and clinical studies have shown treatment effectiveness to correlate with field intensity. For patients with GBM, treatment planning requires generating an array layout that maximizes field intensity at the tumor, which has conventionally been performed with software using morphometric inputs and predefined field simulations from healthy head models. In contrast, SBTP utilizes full contouring of the tumor and abnormal tissue types within the tumor bed, assigns tissue-specific electrical properties, simulates the whole brain field distribution for each patient, and generates an array layout that maximizes power density (PD) to a defined region of interest. PD, a dose metric deriving from field intensity, quantifies the rate of energy delivered to the tissue. This retrospective analysis compared dose metrics between array layouts planned using SBTP vs non-SBTP (NovoTAL) with head-flexible arrays.Materials/Methods:
A retrospective cohort of patients with newly diagnosed GBM initiating TTFields was assembled. Cohort selection criteria included a prior NovoTAL layout plan, unifocal disease per MRI, and sufficient MRI quality for segmentation. Tumor segmentation was done by an independent medical team and reviewed by a radiologist. For SBTP-generated layouts, the region of interest for dose optimization included enhancing tumor plus a 3 mm margin. For NovoTAL layouts, dose was measured for the same region of interest. Calculated dose metrics were normalized to an input current of 2 Amps and included local minimum power density (LMiPD; mW/cm3), local minimum field intensity (LMiFI; V/cm), and local average field intensity (LAFI; V/cm). Volumetric dose coverage was analyzed for the combined cohort and compared between SBTP and NovoTAL.Results:
Among 133 commercial TTFields use cases randomly screened, 60 cases with valid NovoTAL layouts and sufficient MRI quality were included. Average LMiPD (2.83 vs 2.46 mW/cm3), LMiFI (1.57 vs 1.45 V/cm), and LAFI (1.98 vs 1.86 V/cm) to the CTV were significantly higher with SBTP vs the NovoTAL layout (P < 0.001 for each). SBTP was superior to NovoTAL in 63.3% of cases based on LMiPD, non-inferior in 23.3% of cases, and inferior in 13.3% of cases. Average edge-to-edge array distance was increased 62% for layouts generated with SBTP. Additionally, dose-volume coverage to the brain was higher for SBTP vs non-SBTP layouts at LMiPD thresholds of 1 mW/cm3 (96% vs 80%), 2 mWcm3 (66% vs 52%), and 3 mWcm3 (41% vs 31%).Conclusion:
In a large real-world cohort study, dosimetric performance was improved for array layouts generated with SBTP vs non-SBTP, providing rationale for the use of SBTP with head-flexible arrays to better optimize TTFields delivery for patients with newly diagnosed GBM. Future investigations to explore dose-outcome associations are warranted.