First Dosimetric and Biological Verification for Spot-Scanning Hadron Arc Radiation Therapy With Carbon Ions

Area of Science:

• Radiation Oncology
• Medical Physics
• Cancer Biology

Background:

• Spot-scanning hadron arc radiation therapy (SHArc) is an emerging ion beam delivery technique.
• SHArc potentially offers enhanced dose conformity and improved dose-averaged linear energy transfer (LETd) redistribution.
• Understanding its dosimetric and biological effectiveness is crucial for clinical translation.

Purpose of the Study:

• To present the first dosimetric validation of carbon ion SHArc delivery.
• To conduct in vitro verification of carbon ion SHArc.
• To compare SHArc with intensity-modulated particle therapy (IMPT) for treating hypoxic conditions.

Main Methods:

• SHArc and IMPT plans were created for homogeneous physical or biological dose delivery in a PMMA phantom.
• IMPT plans were optimized for LETd-boosting strategies.
• Dosimetric verification used an ionization chamber; in vitro studies employed A549 lung cancer cells for clonogenic survival and 53BP1 foci assays under normoxic and hypoxic conditions.

Main Results:

• Dosimetric measurements and clonogenic assays showed good agreement with planned doses and survival distributions.
• Carbon ion SHArc demonstrated potential to overcome hypoxia-induced radioresistance, as confirmed by survival fractions and foci.
• LETd-boosted IMPT achieved similar target LETd as SHArc but with higher entrance dose; SHArc offered a lower dose bath and larger treatment volume.

Conclusions:

• The first proof-of-principle for carbon ion SHArc delivery was successfully demonstrated.
• Experimental evidence supports SHArc as a promising approach for treating hypoxic tumors.
• SHArc presents an attractive alternative for targeted radiation therapy in challenging tumor environments.