Breast cancer is the most frequently diagnosed cancer and the second leading cause of cancer death in American women. Post-surgery adjuvant radiotherapy (RT) significantly reduced the local recurrence rate. However, many patients develop early adverse skin reactions (EASRs) that impact quality of life and treatment outcomes.

We evaluated an inflammatory biomarker, C-reactive protein (CRP) in predicting RT-induced EASRs in 159 breast cancer patients undergoing RT. In each patient, we measured pre- and post-RT plasma CRP levels using a highly-sensitive ELISA CRP assay. RT-induced EASRs were assessed at weeks 3 and 6 using the National Cancer Institute Common Toxicity Criteria (v3.0). Association between EASRs and CRP levels were assessed using logistic regression models after adjusting for potential confounders.

RT-induced grade 2+ EASRs were observed in 8 (5%) and 80 (50%) patients at weeks 3 and 6 (end of RT), respectively. At the end of RT, significantly higher proportion of African Americans developed grade 3 EASRs (13.8% vs. 2.3% in others); grade 2+ EASRs were significantly associated with: change of CRP>1 mg/L (OR=2.51; 95%CI=1.06, 5.95, p=0.04), obesity (OR=2.08; 95%CI=1.03, 4.21, p=0.04), or combined both factors (OR=5.21; 95%CI=1.77, 15.38, p=0.003).

This is the first study to demonstrate that an inflammatory biomarker CRP is associated with RT-induced EASRs, particularly combined with obesity.

Future larger studies are warranted to validate our findings and facilitate the discovery and development of anti-inflammatory agents to protect normal tissue from RT-induced adverse effects and improve quality of life in breast cancer patients undergoing RT.