OBJECTIVE : The role of clinician-measured breast length and bra cup size in the development of radiodermatitis over time and the efficacy of using multiple measurements of skin toxicity during radiotherapy were piloted. The feasibility of measures to be used in a larger future study was assessed. METHODS : Participants included women receiving normofractionated or accelerated external breast radiotherapy provided in the supine position using 3-dimensional conformal techniques at a US community cancer center. Acute skin toxicity was assessed using the RTOG scale in 7 areas within the treatment field across 6 timepoints. The total score for the 7 areas was calculated each week. Breast length was measured, examined as an acute radiodermatitis risk factor, and compared against reported bra cup size. RM-ANOVAs examined radiodermatitis using maximum skin toxicity and 7 sites in the radiotherapy field over 6 timepoints. Correlation was implemented to explore the relationship between study variables. RESULTS : Forty women consented to this study. Increase in breast length significantly correlated with increase in maximum RTOG score (p = .04); increased RTOG score in the upper medial breast quadrant (p = .04), upper lateral quadrant (p = .02), lower lateral quadrant (p = .02), inframammary fold (p = .001); with increasing BMI (p = .002) and bra cup size (p = .0003). The clinician-measured breast lengths and participant-reported bra cup sizes were discordant. Participants completed all measures and measurements including breast length. CONCLUSIONS : Our results suggest that measuring breast length and assessing radiodermatitis in multiple areas of the treatment field is feasible. These measures may increase the sensitivity of skin toxicity assessment.