Dose Coverage Dependence on Bolus Thickness In Post-Mastectomy Breast Cancer Treatment
Abstract
Purpose
This study seeks to understand the relationship between bolus thickness and dose coverage for the treatment of post-mastectomy breast cancer patients. With the advent of novel bolus materials and 3D printing, it is possible to use bolus with thicknesses outside of the standard 0.5 cm or 1.0 cm. Such granularity in bolus thickness can be used in tandem with an understanding of how dose coverage depends on bolus thickness for more patient-specific care.
Methods
Dose coverage statistics were collected on plans made for a sample patient with different beam energy and bolus thickness combinations. This patient was planned for beam energies of 10x MV, 15x MV, 6x/10x MV and 6x/15x MV, with bolus thicknesses of 0.2 cm, 0.3 cm, 0.5 cm, 0.8 cm, and 1.0 cm. A total of 20 plans were generated. We recorded V90% and V80% of a 5mm skin rind, 3mm skin rind, 2mm subcutaneous tissue rind, and the chest wall as our dose coverage statistics for each plan.
Results
For all four targets of interest, coverage increases as bolus thickness increases up to 0.5 cm, at which point the coverage statistics plateau and do not improve as bolus thickness increases. This behavior holds over all four beam energy combinations under consideration.
Conclusion
Using thinner bolus can deliver dosimetrically equivalent results to using thicker bolus, meaning it is possible to plan with a daily thinner bolus that is equivalent to every-other-day plans using a thicker bolus. A daily, thin bolus could potentially have a skin-sparing effect, and a daily bolus could minimize the risks during treatment set-up inherent in altering bolus regimes.