In the model, TGF-β1 trajectory group 1 (β = 0.27, p = 0.013), left-sided breast cancer (β = 0.39, p = 0.001) and the use of AI (β = 0.29, p = 0.011) were significantly associated with a reduction in GLS from before RT to 3 years. This evidence concerns the gene TGFB1 and breast cancer.