Association of cancer antigen 15-3 with distant recurrence in immunohistochemically defined breast cancer subtypes in Canadian Cancer Trials Group MA.32.

Abstract

Background: Circulating levels of cancer antigen (CA) 15-3 have been associated with distant breast cancer recurrence; data on breast cancer subtypes are sparse. We examined associations of CA 15-3 with outcomes across immunohistochemically defined breast cancer subtypes in MA.32.

Methods: A total of 3649 participants with T1-3, N0-1, M0 breast cancer were randomly assigned; 2740 (75.1%) provided blood at entry (mean = 278 days postdiagnosis) and 6 months later. Prognostic associations of baseline and 6-month change in CA 15-3 with distant recurrence-free survival (RFS) were examined in luminal (estrogen receptor-positive and/or progesterone receptor-positive, HER2-negative), triple-negative (estrogen receptor, progesterone receptor, HER2 negative) and HER2-positive (any estrogen receptor, progesterone receptor) breast cancer using Cox proportional hazards models.

Results: Mean age was 52 years. Breast cancer was luminal in 1589 (58.7%), triple negative in 655 (24.2%), and HER2 positive in 464 (17.1%) participants. Median follow-up was 96 months. CA 15-3 at study entry was not associated with outcome in any subtype. Rising CA 15-3 at 6 months was associated with poor distant RFS in luminal and triple-negative breast cancer (hazard ratio [HR] per 25% increase = 1.41, P < .0001, and HR = 1.35, P < .0001, respectively). New elevations in CA 15-3 at 6 months were adversely associated with distant RFS in those with luminal or triple-negative breast cancer (HR = 4.14, 95% CI = 2.69 to 6.38; P < .001; and HR = 3.57, 95% CI = 1.59 to 7.99; P = .002, respectively). In HER2-positive breast cancer, CA15-3 was not associated with distant RFS.

Conclusion: Rising CA 15-3 was associated with reduced distant RFS in luminal and triple-negative breast cancer but not in HER2-positive breast cancer.

Clinical trial registration: ClinicalTrials.gov NCT01101438.