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Session: Adaptive Treatment Planning and Delivery [Return to Session]

Retrospective Clinical Evaluation of a Decision-Support Software for Adaptive Radiotherapy of Head & Neck Cancer Patients

S Gros1,2*, A Block1,2, B Lee1,2, B Emami1, A Santhanam3, (1) Loyola University Chicago, Stritch School of Medicine, Department of Radiation Oncology, Maywood, IL, (2) Loyola University Medical Center, Maywood, Illinois, (3) University of California, Los Angeles, Los Angeles, CA


SU-H300-IePD-F6-3 (Sunday, 7/10/2022) 3:00 PM - 3:30 PM [Eastern Time (GMT-4)]

Exhibit Hall | Forum 6

Purpose: To evaluate the clinical need for an automated decision-support software platform for Adaptive Radiation Therapy (ART) of Head-and-Neck cancer (HNC) patients.

Methods: We tested RTapp (SegAna), a new ART software platform for deciding when a treatment replan is needed, to investigate a set of 27 HNC patients’ data retrospectively. For each fraction, RTapp estimated dose distributions and cumulative doses received by targets and OARs from daily CBCT in real-time. RTapp also included a prediction algorithm that analyzed dosimetric parameters (DP) trends against user-specified thresholds to proactively trigger adaptation up to 4 fractions ahead. The DPs evaluated for ART were based on treatment planning dose constraints. Warning (V95<95%) and adaptation (V95<93%) thresholds were set for PTVs, while OAR adaptation endpoints of +10% (DE10) were set for all Dmax and Dmean DPs. Any threshold violation at end-of-treatment (EOT) triggered a review of DP trends to determine the threshold-crossing fraction Fx. The prediction model accuracy was determined as the difference between calculated and predicted DP values with 95% confidence intervals (CI95).

Results: RTapp identified 17/27 studies (63%) for violating PTV coverage or parotids Dmean at EOT. Eleven PTVs had V95<95% (mean coverage decrease of -6.8 ±3.0%) including 5 flagged for adaptation at median Fx=8 (range: 1-18). Seventeen parotids exceeded their Dmean constraints with a median increase of +2.95 Gy (range: 0.99-6.31Gy) at EOT, including 9 with DP>DE10. The differences between predicted and calculated PTV V95 and parotids Dmean was up to 7.6% (mean±CI95: -2.9±4.6%) and 5Gy (mean±CI95: +0.3±1.6Gy), respectively. For parotids, a median Fx of 5 ranged between 1-23 with a lack of specific trend demonstrating that the need for treatment adaptation may be verified for every fraction.

Conclusion: Integrated in an ART clinical workflow, RTapp aids in predicting whether specific treatment would require adaptation up to four fractions ahead of time.


Deformation, Image-guided Therapy, Software


TH- External Beam- Photons: adaptive therapy

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