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

Goodwin PJ, Chen BE, Gelmon KA, Whelan TJ, Ennis M, Ligibel J, Stos PM, Shepherd LE et al.

JNCI cancer spectrum, 2026

3,649 participants

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 =…

How strong is the evidence?

Evidence Hub reads this as a randomized trial, done in people. Its evidence level is 2 of 5 (High · randomized trial). Randomized trials of a reasonable size are the strongest single-study design. Reported size: 3,649 participants or records.

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