Toward a Skin Dose-Area Metric Predictive of Moist Desquamation Using In Vivo Skin Dosimetry and Skin Assessments

Moist desquamation (MD) is a concerning acute side effect of radiation therapy for breast cancer, often seen in skin folds for patients having large or pendulous breasts. In vivo skin dosimetry, clinical assessments, and patient-reported skin reactions were used to determine a relationship between dose-area metrics and the development of MD, to lend insight into skin tolerances and possibly guide future treatment planning dose constraints.

Skin dose was measured using GafChromic film on the inner surface of an early prototype carbon-fiber accessory for breast support to remove the inframammary fold in 20 patients at high risk of developing MD undergoing adjuvant whole breast radiation therapy. Prescribed doses were 42.5 Gray (Gy) in 16 fractions or 50 Gy in 25 fractions using 6 to 15 MV x-rays. To account for fraction size differences, analysis was performed using the equivalent dose in 2 Gy fractions using α/β = 11 (EQD2₁₁). MD was assessed out to 2 weeks post radiation therapy by trained therapists and by a patient-reported outcome questionnaire.

Statistically significant differences in areas receiving 30 to 48 Gy (EQD2₁₁) were observed between patients who did and did not develop MD in the inframammary area. Patients receiving EQD2₁₁ maximum dose ≤ 46 Gy and ≥ 38 Gy to ≤ 50 cm² of their breast skin did not develop MD.

The findings of this study offer insight into the relationship between skin toxicity and areas of skin irradiated to doses up to 50 Gy. Potential skin dose constraints to test in future studies to prevent MD are suggested.