- Having a single nucleotide polymorphism (SNP, C-509T) in the promoter region of the transforming growth factor β (TGFβ1) gene is associated with an increased risk for radiation-induced breast fibrosis 3 years after radiotherapy (RT).
Why this matters
- This is the first study to evaluate prospectively a genomic marker for radiation fibrosis.
- Findings may help to counsel patients and identify potential treatment strategies.
- Cohort of 174 patients nested within an open-label randomized controlled trial who had pathologically confirmed stage 0-IIA breast cancer and who received whole-breast irradiation after breast-conserving surgery.
- Primary outcome: grade ≥2 breast fibrosis at 3 years post-RT.
- Breast fibrosis was assessed by physicians using the Late Effects Normal Tissue/Subjective, Objective, Medical Management, Analytic scale.
- Funding: Conquer Cancer Foundation.
- Patients with the polymorphism (51% of the cohort) were more likely to have breast fibrosis than those without (13.8% vs 3.8%, absolute difference of 10%; P=.02).
- On multivariate analysis, the only factors found to increase breast fibrosis risk were having the polymorphism (OR, 4.47; P=.02) and fair-to-poor postoperative cosmetic outcome (OR, 7.09; P<.001>
- Potential underestimation of effect size because of late toxicities.
- Observational design.