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Phys Med. 2016 Feb;32(2):331-42. doi: 10.1016/j.ejmp.2015.12.009. Epub 2016 Feb 13.

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

Author information

1
Department of Radiation Oncology, Mayo Clinic, 200 First St. SW, Rochester, MN 55901, USA; Department of Radiation Oncology, Mayo Clinic Hospital, 5777 E. Mayo Blvd., Phoenix, AZ 85054, USA.
2
Department of Radiation Oncology, Mayo Clinic, 200 First St. SW, Rochester, MN 55901, USA.
3
Department of Radiation Oncology, Mayo Clinic Hospital, 5777 E. Mayo Blvd., Phoenix, AZ 85054, USA.
4
Department of Radiation Oncology, Mayo Clinic Hospital, 5777 E. Mayo Blvd., Phoenix, AZ 85054, USA. Electronic address: Tryggestad.Erik@mayo.edu.

Abstract

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.

KEYWORDS:

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

PMID:
26883369
DOI:
10.1016/j.ejmp.2015.12.009
[Indexed for MEDLINE]

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