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Session: Best of Professional [Return to Session]

Adaptive Planning Using PreciseART for Glioblastoma Patient Wearing Tumor Treating Fields Device

Y Qin*, R Tobias, R Foster, M Pankuch, Northwestern Medicine Chicago Proton Center, Warrenville, IL

Presentations

MO-E115-BOP-F1-4 (Monday, 7/11/2022) 1:15 PM - 1:45 PM [Eastern Time (GMT-4)]

Exhibit Hall | Forum 1

Purpose: In radiation therapy we are seeing more glioblastoma patients wearing tumor treating fields (TTF) device. The location of TTF electrodes changes every few days as they were taken off and repositioned on the scalp to reduce skin irritation. This study aimed to evaluate the dosimetric impact of changing electrode locations throughout a 15 fraction Radixact treatment, utilizing the adaptive planning module of PreciseART (Accuray Inc).

Methods: Patient with Optune@ TTF attached on scalp was placed in a head mask and scanned using MVCT on Radixact. A plan with 4005cGy prescription was created using Precision treatment planning system. Entrance through the electrodes were not avoided due to their repositioning every 3 days. For each fraction, an MVCT was acquired. The treatment plan was recalculated on the MVCT after applied shifts. A new composite DVH was generated after each fraction. A total composite dose was summarized after treatment completion. All organs-at-risk (OAR) doses are analyzed.

Results: Compared to the planned dose, actual delivered D95% PTV was 1.4% lower; maximum dose to the brainstem was 4.5% lower; maximum dose to the brain was 2.3% higher; all other OAR dose metrics agree with the plan metrics within 24cGy. 3D dose difference map revealed the largest dose difference occurred outside of PTV in low dose region. Replan constraint threshold was not exceeded. No additional processing time was needed as PreciseART automatically recalculated and added each fraction after treatment. Physician was able to view the composite plan anytime. Automatic alert would be sent if dose deviation threshold was crossed.

Conclusion: In this case study, changing location of TTF electrodes did not result in clinically significant dose difference. PrecisionART provided a convenient platform for tracking delivered dose on these intrinsically difficult setup cases.

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