An online adaptive plan library approach for intensity modulated proton therapy for head and neck cancer

Radiother Oncol. 2022 Nov;176:68-75. doi: 10.1016/j.radonc.2022.09.011. Epub 2022 Sep 20.


Background and purpose: In intensity modulated proton therapy (IMPT), the impact of setup errors and anatomical changes is commonly mitigated by robust optimization with population-based setup robustness (SR) settings and offline replanning. In this study we propose and evaluate an alternative approach based on daily plan selection from patient-specific pre-treatment established plan libraries (PLs). Clinical implementation of the PL strategy would be rather straightforward compared to daily online re-planning.

Materials and methods: For 15 head-and-neck cancer patients, the planning CT was used to generate a PL with 5 plans, robustly optimized for increasing SR: 0, 1, 2, 3, 5 mm, and 3% range robustness. Repeat CTs (rCTs) and realistic setup and range uncertainty distributions were used for simulation of treatment courses for the PL approach, treatments with fixed SR (fSR3) and a trigger-based offline adaptive schedule for 3 mm SR (fSR3OfA). Daily plan selection in the PL approach was based only on recomputed dose to the CTV on the rCT.

Results: Compared to using fSR3 and fSR3OfA, the risk of xerostomia grade ≥ II & III and dysphagia ≥ grade III were significantly reduced with the PL. For 6/15 patients the risk of xerostomia and/or dysphagia ≥ grade II could be reduced by > 2% by using PL. For the other patients, adherence to target coverage constraints was often improved. fSR3OfA resulted in significantly improved coverage compared to PL for selected patients.

Conclusion: The proposed PL approach resulted in overall reduced NTCPs compared to fSR3 and fSR3OfA at limited cost in target coverage.

Keywords: Daily adaptive radiotherapy; Head and neck cancer; Intensity modulated proton therapy; Inter-fraction motion; Plan library; Proton therapy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Deglutition Disorders*
  • Head and Neck Neoplasms* / radiotherapy
  • Humans
  • Organs at Risk
  • Proton Therapy* / adverse effects
  • Proton Therapy* / methods
  • Radiotherapy Dosage
  • Radiotherapy Planning, Computer-Assisted / methods
  • Radiotherapy, Intensity-Modulated* / adverse effects
  • Radiotherapy, Intensity-Modulated* / methods
  • Xerostomia*