High-sensitivity C-reactive protein (hs-CRP) as a biomarker for trastuzumab-induced cardiotoxicity in HER2-positive early-stage breast cancer: a pilot study.

Monitoring of left ventricular ejection fraction (LVEF) is the current standard for detection of trastuzumab-induced cardiotoxicity; however, time-to-diagnosis and cost of assessment are suboptimal in women with early-stage breast cancer. We assessed the utility of B-type natriuretic peptide (BNP), high-sensitivity C-reactive protein (hs-CRP), and cardiac troponin I (cTnI) as serum biomarkers for early detection of trastuzumab-induced cardiotoxicity. Fifty-four women with human epidermal growth factor receptor 2 (HER2)-positive early-stage breast cancer were prospectively enrolled, and the relationship between elevated serum BNP, hs-CRP, and cTnI levels and clinically significant decreases in LVEF was examined. LVEF was monitored at 3-4 month intervals during trastuzumab treatment. Laboratory testing for candidate biomarkers was repeated every 3 weeks with each cycle of trastuzumab. Trastuzumab-induced cardiotoxicity was defined as a decrease in LVEF of ≥15% or to a value below 50%. A clinically significant decrease in LVEF was observed in 28.6% of women. Abnormal hs-CRP (≥3 mg/L) predicted decreased LVEF with a sensitivity of 92.9% (95% CI 66.1-99.8) and specificity of 45.7% (95% CI 28.8-63.4), and subjects with normal hs-CRP levels (<3 mg/L) have 94.1% negative predictive 94.1% (95% CI 70.3-99.9) suggesting that normal hs-CRP levels may be associated with low future risk for decreased LVEF; however, no association with BNP or cTnI was observed. A false positive would have a relatively low associated cost in breast cancer patients undergoing adjuvant trastuzumab therapy and would indicate continuation of routine observation during treatment through traditional means. The maximum hs-CRP value was observed a median of 78 days prior to detection of cardiotoxicity by decreased LVEF, and those with normal levels were at lower risk for cardiotoxicity. Regular monitoring of hs-CRP holds promise as a biomarker for identifying women with early-stage breast cancer at low risk for asymptomatic trastuzumab-induced cardiotoxicity. To our knowledge, this is the first study documenting the utility of a less expensive, reproducible, easily obtainable biomarker with rapid results for evaluating cardiotoxicity related to trastuzumab therapy.