Tumor-associated mononuclear cells in the tumor bed of triple-negative breast cancer associate with clinical outcomes in the post-neoadjuvant chemotherapy setting

Abstract

Purpose: To evaluate the clinical role of tumor-associated macrophages, including foamy (FM) and hemosiderin-laden macrophages (HLM) in the tumor bed (TB) of triple-negative breast cancer (TNBC) post-neoadjuvant chemotherapy (NACT).

Methods: We conducted a pathologic review of 129 women, diagnosed with TNBC between 2002 and 2016 at our institute. The residual cancer burden (RCB) was calculated. We estimated the percentage of tumor-infiltrating lymphocytes (TILs) in the core needle biopsy (CNB), and FM, HLM, and TILs (in TB) [the combined cells are designated as tumor-associated mononuclear cells (TAMNC)]. The information on patient demographics, chemotherapy regimen, recurrence-free survival (RFS), and overall survival (OS) was extracted from the medical records.

Results: Pathologic complete response (pCR) was achieved in 34.1% of the women. TILs (10% increment in CNB) only were associated with pCR in the multivariable analysis [odds ratio 1.04 (1.02, 1.06) (p = 0.0003)]. Immune cells associated with better OS included TAMNC (≤ 30%) [hazard ratio (HR) 4.32 (1.93, 9.66) (p = 0.0004)], and FM (0%) [HR 2.30 (1.06, 4.98) (p = 0.036)]. While increased HLM (10% increment) was statistically significant with HR 0.93 and 95% CI (0.88 to 0.98) (p = 0.0061), using a cutoff of 0%, HLM (0%: negative vs. ≥ 1%: positive) achieved only borderline significance with HR 2.05 (0.98, 4.31) (p = 0.058). Similarly, these immune cells were also associated with better RFS: TAMNC (≤ 30%) [HR 4.57 (2.04, 10.21) (p = 0.0002)], FM (0%) [HR 2.80 (1.23, 6.35) (p = 0.014)], and HLM (0%) [HR 2.34 (1.07, 5.11) (p = 0.03)]. TILs (in TB) were not associated with any clinical outcomes.

Conclusions: Although TILs may play a role in the response to NACT, they may not be critical to the prognosis after NACT. Instead, FM and HLM may assume this role. More studies are warranted.

Keywords: Foamy macrophages; Hemosiderin laden macrophages; Neoadjuvant chemotherapy; Triple-negative breast cancer; Tumor microenvironment; Tumor-infiltrating lymphocytes.