  Stereotactic body radiation therapy (SBRT) and hypofractionation using
pencil-beam scanning (PBS) proton therapy (PBSPT) is an attractive option for
thoracic malignancies. Combining the advantages of target coverage conformity
and critical organ sparing from both PBSPT and SBRT, this new delivery
technique has great potential to improve the therapeutic ratio, particularly
for tumors near critical organs. Safe and effective implementation of PBSPT
SBRT/hypofractionation to treat thoracic malignancies is more challenging than
the conventionally-fractionated PBSPT due to concerns of amplified
uncertainties at the larger dose per fraction. NRG Oncology and Particle
Therapy Cooperative Group (PTCOG) Thoracic Subcommittee surveyed US proton
centers to identify practice patterns of thoracic PBSPT SBRT/hypofractionation.
From these patterns, we present recommendations for future technical
development of proton SBRT/hypofractionation for thoracic treatment. Amongst
other points, the recommendations highlight the need for volumetric image
guidance and multiple CT-based robust optimization and robustness tools to
minimize further the impact of uncertainties associated with respiratory
motion. Advances in direct motion analysis techniques are urgently needed to
supplement current motion management techniques.
