While prognostic factors in early stage breast cancer are well documented, few studies have examined predictors of the rate of metastatic progression. The purpose of this study was to examine cytotoxic T-cell lymphocyte (CTL) count as a marker of disease status in women with metastatic breast cancer. This study examined CTL subset counts as predictors of subsequent survival in 113 women with metastatic or recurrent breast cancer. Samples were measured by flow cytometry using monoclonal antibodies for cell surface antigens for percentages and absolute numbers of CTLs (CD3/CD8), total lymphocytes, T cells (CD3), helper T cells (CD3/CD4), and total white blood cell (TWC) count. Higher CTL counts emerged as a significant predictor of longer survival up to 7 years later (Wald = 7.40, p = 0.007; Cox regression model). The relationship of higher CTL count with enhanced survival was independent of the effects of medical treatment. CTLs were significantly associated with TWC count (r = 0.42, p < 0.001). However, TWC count was not associated with subsequent survival time. Higher CTL count was associated with Karnofsky performance status (r = 0.27, p = 0.004). However, after adjustment for the Karnofsky score, the CTL count/survival relationship remained significant (Wald = 4.33, p = 0.038). In conclusion, there is a robust relationship between CTL count and survival that is independent of the effects of medical treatments, TWC count, and Karnofsky performance status. Moreover, a reduced CTL count may be a mediator or marker of more rapid disease progression in metastatic breast cancer.
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