The importance of regulating and improving the tumor immune microenvironment is increasingly being recognized. While it has been reported that therapeutic agents for hyperlipidemia, in particular statins, can induce cancer cell growth suppression and anti-metastatic effects in breast cancer, few studies have investigated the correlation between improvement of lipid metabolism and antitumor immune response and cancer prognosis in vivo.
Except for patients with ductal carcinoma in situ, 938 breast cancer patients treated with curative surgery were examined. The correlation between serum levels of total-cholesterol and triglyceride, and clinicopathological features, including neutrophil-to-lymphocyte ratio (NLR) and tumor-infiltrating lymphocytes (TILs), and prognosis was evaluated retrospectively.
194 patients were receiving treatment for hyperlipidemia. Recurrence-free survival (RFS) and overall survival (OS) did not differ significantly between users of the drug for hyperlipidemia or non-users (p = 0.782, log-rank) (p = 0.304, log-rank). Among postmenopausal patients with hormone receptor (HR)-positive/human epidermal growth factor receptor 2 (HER2)-negative breast cancer, who were treated for hyperlipidemia, the group with good serum lipid level had significantly better RFS (p = 0.014, log-rank). Also, good serum lipid control was significantly correlated with low-NLR (p = 0.024) and high-TILs in resected tumors (p = 0.039). In addition, lipophilic statin users had lower recurrence rate than hydrophilic statin users (8.2 % vs 16.0 %).
After curative surgery, almost postmenopausal patients with HR-positive breast cancer are treated with adjuvant endocrine therapy, including aromatase inhibitor (AI). Recently, it is reported that AI treatment increases local aromatase activity and promotes autocrine estrogen signaling in AI-resistant metastatic tumor. Our study suggests that good control of lipid metabolism may have a relationship with improvement in these tumor immune microenvironment and favorable outcome.
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