Optimal Timing of Organs-at-Risk-Sparing Adaptive Radiation Therapy for Head-and-Neck Cancer Under Re-Planning Resource Constraints

Authors

Fatemeh Nosrat
Cem Dede
Lucas B McCullum
Raul Garcia
Abdallah S R Mohamed
Jacob G Scott
James E Bates
Brigid A McDonald
Kareem A Wahid
Mohamed A Naser
Renjie He
Aysenur Karagoz
Amy C Moreno
Lisanne V van Dijk
Kristy K Brock
Jolien Heukelom
Seyedmohammadhossein Hosseinian
Mehdi Hemmati
Andrew J Schaefer
Clifton D Fuller

Publication Date

1-1-2025

Journal

Physics and Imaging in Radiation Oncology

Abstract

Background and purpose: Prior work on adaptive organ-at-risk (OAR)-sparing radiation therapy has typically reported outcomes based on fixed-number or fixed-interval re-planning, which represent one-size-fits-all approaches and do not account for the variable progression of individual patients' toxicities. The purpose of this study was to determine the personalized optimal timing of re-planning in adaptive OAR-sparing radiation therapy, considering limited re-planning resources, for patients with head and neck cancer (HNC).

Materials and methods: A novel Markov decision process (MDP) model was developed to determine optimal timing of re-planning based on the patient's expected toxicity, characterized by normal tissue complication probability (NTCP), for four toxicities. The MDP parameters were derived from a dataset comprising 52 HNC patients treated between 2007 and 2013. Kernel density estimation was used to smooth the sample distributions. Optimal re-planning strategies were obtained when the permissible number of re-plans throughout the treatment was limited to 1, 2, and 3, respectively.

Results: The MDP (optimal) solution recommended re-planning when the difference between planned and actual NTCPs (ΔNTCP) was greater than or equal to 1%, 2%, 2%, and 4% at treatment fractions 10, 15, 20, and 25, respectively, exhibiting a temporally increasing pattern. The ΔNTCP thresholds remained constant across the number of re-planning allowances (1, 2, and 3).

Conclusion: In limited-resource settings that impeded high-frequency adaptations, ΔNTCP thresholds obtained from an MDP model could derive optimal timing of re-planning to minimize the likelihood of treatment toxicities.

Keywords

Personalized adaptive radiation therapy, Organs at risk, Normal tissue complication probability, Markov decision process, Optimal strategy, Markov decision process, Normal tissue complication probability, Optimal strategy, Organs at risk, Personalized adaptive radiation therapy

DOI

10.1016/j.phro.2025.100715

PMID

40123771

PMCID

PMC11926540

PubMedCentral® Posted Date

1-27-2025

PubMedCentral® Full Text Version

Post-print

Published Open-Access

yes