The following is a summary of “Skin dose-volume predictors of moderate-severe late side effects after whole breast radiotherapy,” published in the February 2024 issue of Oncology by Ciccheti et al.

Radiation-induced toxicity remains a significant concern following whole breast radiotherapy, potentially impacting the quality of life for a considerable number of patients. Their objective was to develop a Normal Tissue Complication Probability (NTCP) model capable of predicting late toxicities by integrating dosimetric parameters of the breast dermis with relevant clinical factors. Researchers used a retrospective analysis of a large mono-institutional cohort comprising early-stage breast cancer patients treated between 2009 and 2017 (n = 1066) to define the skin structure as the outer CT body contour’s 5 mm inner isotropic expansion. Patients received tangential-field radiotherapy, delivering 40 Gy in 15 fractions to the entire breast. 

Toxicity assessments were conducted during follow-up using SOMA/LENT scoring, with the study endpoint focused on moderate-severe late toxicity, specifically Fibrosis-Atrophy-Telangiectasia-Pain (FATP G ≥ 2) occurring within 42 months post-radiotherapy completion. Employing a machine learning pipeline, the study group constructed a logistic model that amalgamated clinical factors with absolute skin dose-volume histogram (DVH) parameters to predict late toxicity outcomes. The observed FATP G2 + rate stood at 3.8 %, with 40 out of 1,066 patients experiencing side effects. Cross-validation techniques were employed following variable preprocessing to identify the optimal performing model. Ultimately, a 4-variable model was selected, incorporating Post-Surgery Cosmetic alterations (Odds Ratio, OR = 7.3), Aromatase Inhibitors (as a protective factor with OR = 0.45), V20 Gy (50 % of the prescribed dose, OR = 1.02), and V42 Gy (105 %, OR = 1.09). Additionally, factors were transformed into an adjusted V20Gy parameter. 

In conclusion, their study quantified the association between late reactions and skin DVH parameters in delivering 40 Gy/15 fr, highlighting the independent role of V20 and V42. Notably, a limited number of clinical factors significantly influenced the risk profile for late toxicity development.

Source: sciencedirect.com/science/article/abs/pii/S016781402400104X