Spot-scanned pancreatic stereotactic body proton therapy: A dosimetric feasibility and robustness study

Terence T. Sio, Kenneth W. Merrell, Chris J. Beltran, Jonathan B. Ashman, Kathleen A. Hoeft, Robert C. Miller, Thomas J. Whitaker, Stephanie K. Wurgler, Erik J. Tryggestad

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


Purpose: We explored the dosimetric potential of spot-scanned stereotactic body proton therapy (SBPT) for pancreatic cancer. Methods: We compared SBPT to stereotactic body intensity-modulated radiotherapy (SB-IMRT) in 10 patients. We evaluated 3 variables in SBPT planning: (1) 4 and 6 mm spot size; (2) single vs. multi-field optimization (SFO vs. MFO); and (3) optimization target volume (OTV) expansion. Robustness analysis was performed with unidirectional isocenter shifts of ±3 mm in x, y, and z and ±3% stopping power uncertainties. Results: SBPT plans had lower V10Gy for the stomach and small and large bowels. Under static robustness, a 5 mm OTV and SFO-6 mm spot size represented the best compromise between target and normal structure. A 4-mm spot-size and 3 mm OTV resulted in significant target underdosing with deformable dose accumulation analysis. Conclusions: This study provides a critical basis for clinical translation of spot size, optimization technique, and OTV expansion for pancreatic SBPT.

Original languageEnglish (US)
Pages (from-to)331-342
Number of pages12
JournalPhysica Medica
Issue number2
StatePublished - Feb 1 2016


  • Intensity-modulated radiation therapy
  • Pancreatic cancer
  • Proton plan robustness
  • Spot-scanned proton therapy
  • Stereotactic body proton therapy
  • Stereotactic body radiation therapy

ASJC Scopus subject areas

  • Biophysics
  • Radiology Nuclear Medicine and imaging
  • General Physics and Astronomy


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