Magnetic Resonance Imaging Features Associated with a High and Low Expression of Tumor-Infiltrating Lymphocytes: A Stratified Analysis According to Molecular Subtypes.

Simple Summary: Tumor-infiltrating lymphocytes (TILs) in breast cancer are known as promising predictive biomarkers associated with responses to neoadjuvant chemotherapy and immunotherapy, and they are also prognostic biomarkers associated with progression-free survival. The rate of high vs. low TILs in hormonal receptor 2-positive, HER2-negative (HR+/HER2−), HER2-positive (HER2+), and Triple-negative (TN) patients were compared. The high-TIL cases significantly increased from 18% in HR+ to 37% in HER2+ and 44% in TN. The MRI features among these three subtypes, as well as the features between high- vs. low-TIL cases in each subtype, were compared. The HER2+ cancer patients were more likely to present non-mass enhancement (NME). In the HR+ cohort, high-TIL cases were more likely to result in peritumoral edema. In the TN subjects, high-TIL cases were more likely to present as regular shapes and circumscribed margins. The results of this study suggest that TIL status may be determined from pre-treatment diagnostic MRI to assist in the selection of optimal treatments. A total of 457 patients, including 241 HR+/HER2− patients, 134 HER2+ patients, and 82 TN patients, were studied. The percentage of TILs in the stroma adjacent to the tumor cells was assessed using a 10% cutoff. The low TIL percentages were 82% in the HR+ patients, 63% in the HER2+ patients, and 56% in the TN patients (p < 0.001). MRI features such as morphology as mass or non-mass enhancement (NME), shape, margin, internal enhancement, presence of peritumoral edema, and the DCE kinetic pattern were assessed. Tumor sizes were smaller in the HR+/HER2− group (p < 0.001); HER2+ was more likely to present as NME (p = 0.031); homogeneous enhancement was mostly seen in HR+ (p < 0.001); and the peritumoral edema was present in 45% HR+, 71% HER2+, and 80% TN (p < 0.001). In each subtype, the MR features between the high- vs. low-TIL groups were compared. In HR+/HER2−, peritumoral edema was more likely to be present in those with high TILs (70%) than in those with low TILs (40%, p < 0.001). In TN, those with high TILs were more likely to present a regular shape (33%) than those with low TILs (13%, p = 0.029) and more likely to present the circumscribed margin (19%) than those with low TILs (2%, p = 0.009). [ABSTRACT FROM AUTHOR]

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