Quantitative assessment of infiltrating macrophages could provide clues for predicting the prognosis in the patients with immune checkpoint inhibitor-associated myocarditis
H Yamamoto, T Nishikawa, T Otani, T Yasui, K Hatakeyama, M FujitaAbstract
Background
Pathological findings, such as infiltration of T cells into myocardial tissue are useful in diagnosing immune checkpoint inhibitor-associated myocarditis (irMyocarditis). However, there is a lack of evidence regarding the infiltration of macrophages (CD68- or CD163-positive cells) in irMyocarditis and the correlation between the severity of macrophage infiltration and the prognosis of the patients with irMyocarditis remains to be elucidated.
Purpose
The objective of this study is to quantitatively assess the severity of macrophage infiltration by mechanically counting the number of CD68- or CD163-positive cells in myocardial specimens from the patients with irMyocarditis and to elucidate how the severity of macrophage infiltration correlates with the prognosis of the patients with irMyocarditis.
Methods
This multicentre retrospective observational study included 37 patients diagnosed with irMyocarditis. Myocardial specimens were immunostained using antibodies against CD68 or CD163, then, the number of positive cells was automatedly counted using a bioimage analysis software. We evaluated the number of cells per high power field (HPF) as both the average among the whole tissue and the hotspot, the HPF where the density of cells was highest in the tissue. The primary outcome of this study was major adverse cardiovascular events (MACE), a composite outcome of cardiovascular death, ventricular tachyarrhythmia, and complete atrioventricular block, and the secondary outcomes were acute decompensated heart failure (ADHF) and immune related adverse events (irAEs) in organs other than the heart.
Results
The number of infiltrating macrophages was significantly greater in the group of patients with MACE compared with the group of patients without MACE for CD68- or CD163-positive cells. This significant difference was observed both in the average of whole tissue and in the hotspot. The median of CD68-positive cells in the hotspot was 250 cells/HPF in MACE(+) group whereas 34 cells/HPF in MACE(-) group (p=0.012). The median of CD163-positive cells in the hotspot was 234 cells/HPF in MACE(+) group whereas 22 cells/HPF in MACE(-) group (p=0.0044) (Figure 1). When we defined the outcomes as the composite of MACE or ADHF, the median of CD163-positive cells in the hotspot was significantly greater in MACE/ADHF(+) group than in MACE/ADHF(-) group (73 cells/HPF vs. 17 cells/HPF; p=0.001)(Figure 2). We also evaluated CD163/CD68 ratio to investigate how the macrophage composition, M1- or M2-dominant, affects the prognosis of the patients with irMyocarditis. As a result, the patients who developed noncardiac irAEs following the onset of irMyocarditis had significantly lower CD163/CD68 ratio than the patients without noncardiac irAEs (0.08 vs. 0.68; p=0.046).
Conclusion
Quantitative assessment of infiltrating macrophages could provide clues for predicting the prognosis, such as MACE, ADHF, or following irAEs, in the patients with irMyocarditis.Figure 1 Figure 2