161 - Evaluating the Relationship of Baseline Skin Pigmentation Phenotype on the Evolution of Radiation Dermatitis
Presenter(s)
A. K. Yoder1, A. F. M. Salem Jr2, K. N. Nordlund2, R. Lin2, S. F. Shaitelman2, C. D. Fuller1, A. Lee3, C. R. Goodman2, B. A. Guadagnolo1, A. J. Bishop1, A. Farooqi1, and D. Mitra1; 1Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 2The University of Texas MD Anderson Cancer Center, Houston, TX, 3Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, TX
Purpose/Objective(s): Radiation dermatitis (RD) is a common toxicity of radiotherapy (RT) that can cause pain, desquamation, and increased risk of infection and treatment breaks. We hypothesize that baseline skin pigmentation alters the physical manifestation of RD progression such that standard RD grading scales may inadequately capture the dynamic range of patients with darker pigmentation.
Materials/Methods: Between 2022 – 2024 we enrolled 60 patients on a prospective study to evaluate biophysical properties of skin during fractionated RT (<3 Gy/fraction). Eligible patients received skin D50 cc>48 Gy. Weekly while on treatment, erythema and melanin were measured within the RT field using a handheld spectrophotometer (Mexameter MX-18). Matched timepoint photos were graded by 3 blinded radiation oncologists using the RTOG Modified RD Scale. For analysis, patients were grouped by established baseline Fitzpatrick (FZ) melanin levels. Lighter baseline pigmentation was defined as melanin <250 (FZ 1-3) vs. darker baseline skin pigmentation defined as melanin >250 (FZ 4-6). RD, erythema, and melanin readings during treatment were compared between cohorts using independent t-tests.
Results: Fifty-eight patients receiving RT were eligible for analysis: 20 patients with breast cancer, 19 with head and neck malignancies, and 19 with sarcoma. The distribution by race and ethnicity was: 35 non-Hispanic White (57%), 9 Hispanic (14%), 7 Asian (11%), and 4 non-Hispanic Black (6%). Fifty patients (83%) had FZ 1-3 skin type (mean melanin 63 (sd 83) while 10 patients (17%) had FZ 4-6 skin type (mean melanin 281 (sd 178). Median RT dose was 60 Gy in 2 Gy/fraction in both cohorts. Mean skin D50cc was similar between the two cohorts (FZ 1-3 55.6Gy (sd 7.8) vs FZ 4-6 58.7Gy (sd 4.6), p=0.29). Peak blinded RD grade was significantly higher in the FZ 4-6 cohort (2.5 (sd 0.4)) vs. FZ 1-3 cohort (2.1 (sd 0.6), p=0.017). Maximum change in erythema from baseline was higher in patients with FZ 1-3 (185 (sd 82) vs FZ 4-6 70 (sd 32), p<0.001). However, peak change in melanin was higher in patients with FZ 4-6 (281 (sd 178) vs FZ 1-3 63 (sd 83), p<0.001). While RD rose steadily for FZ 1-3 patients (average of 0.30 (sd 0.11) change per week for weeks 1-3 and 0.23 (sd 0.04) for weeks 4-6), this was not the case for patients with FZ 4-6 skin, where minimal change was seen from weeks 1-3 (average change of 0.16 (sd 0.13)) followed by a much larger average change from weeks 4-6 (0.69 (sd 0.08)).
Conclusion: Patients with lighter skin pigmentation (FZ 1-3) exhibit a steady increase in clinical RD and quantitative erythema during fractionated RT. In contrast, patients with darker skin pigmentation (FZ 4-6) exhibit a later spike in clinical RD with progressive hyperpigmentation and minimal induction of erythema. Given that conventional RD grading scales lack granularity in assessing hyperpigmentation, existing metrics are inadequate in assessing RT-induced skin toxicity for patients with darker baseline skin pigmentation.