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Treating the Contents and Not the Container: Dosimetric Study of Hair-sparing Whole Brain Intensity Modulated Radiation Therapy

Hematogenous metastatases are the most common adult central nervous system malignancies. The standard treatment of these patients continues to include whole brain radiation. An unavoidable toxicity of this treatment is acute iatrogenic alopecia. This alopecia is a significant cause of patient distress. Our purpose was to quantify the sparing of the hair bearing skin that could be achieved by using a complex hair-sparing approach. To achieve this goal, we treat an anthropomorphic phantom with both conventional and inverse-planned intensity-modulated portals. The skin dose was evaluated through dose-volume histograms and thermo-luminescent dosimetry. The median calculated dose was reduced by 38%. The average measured dose at five surface points was reduced by 53% — from 95% of the prescription dose with the conventional plan, to 44%, with the IMRT plan. This sparing was achieved while maintaining adequate target coverage. Because of the low radiation tolerance of the hair follicle, this dose reduction is not expected, on its own, to eliminate radiation alopecia but bears promise in combination with other toxicity-sparing strategies.