Molecular subtypes of breast cancer: Can it be determinant for preoperative MRI planning?

Abstract

Abstract Background The purpose of this study was to determine whether molecular subtype, which is an important prognostic factor for breast cancer, can be used as a determinant for preoperative breast MRI indication. Concordantly, we also searched for whether women with luminal A subtype tumors with better prognosis may not require preoperative MRI for staging.Materials and methods A total of 150 women who underwent preoperative breast MRI with a diagnosis of breast cancer from January 2015 through December 2018 were included in the study. Subtypes were classified as luminal A, luminal B, HER-2 overexpressing, and triple negative according to immunohistochemical markers. Preoperative breast MRI findings were evaluated due to the ACR breast lexicon. Morphological, kinetic and diffusion features or the presence of additional findings on MRI were compared with molecular subtypes. Statistical analyses were performed between the luminal A subtype and the other subtypes.Results The subtype distribution was luminal A, 30.7%; luminal B, 50%; HER-2 over-expressing, 10%; and triple negative, 9.3%. Tumor size was significantly higher in luminal A subtype than in non-luminal A subtypes (p = 0.03). There was no statistically significant difference between the two groups according to morphological, kinetic and diffusion features; the presence of multifocal, multicentric, or contralateral disease; or tumor extension. Additionally, there was no statistically significant difference between the two groups according to nipple, skin, pectoral muscle involvement or the presence of axillary and internal mammary lymph nodes.Conclusions The presence of additional findings and local extensive disease in women with breast cancer is seen in luminal A subtype with very high rates. In addition, luminal A subtype was found to be related to increased tumor size. Non-mass enhancements, which are less detectable in other imaging modalities, are also seen in luminal A subtype at the same rate as other molecular subtypes. Consequently, our study showed that preoperative breast MRI must be performed in all molecular subtype groups.