Significance of iodine symporter for prognosis of the disease course and efficacy of neoadjuvant chemotherapy in patients with breast cancer of luminal and basal subtypes

Abstract

The aim of the research was to study the relation between expression of Na⁺/I⁻symporter (NIS) in breast cancer (BC) of different molecular subtypes and sensitivity of BC cells to neoadjuvant chemotherapy (NACT) and to assess whether NIS expression may be used as a predictive marker of treatment efficacy. Materials and Methods: The study included 148 women with BC of stage II–III who were treated at the Precarpathian Clinical Oncology Center during 2012–2017. All patients were treated with NACT that included 2–6 cycles of chemotherapy by FAC, AC scheme with 21 day intervals. NACT efficacy was evaluated every 2 cycles by mammography according to RECIST criteria. Morphological and immunohistochemical study of NIS expression was performed by the standard methods on paraffin sections of surgically resected tumors. Results: The heterogeneity of different molecular BC subtypes regarding response to the NACT has been found. Her2/neu-positive and basal BC subtypes were the least susceptible to the NACT (p < 0.05). It was shown that NIS expression is related to the sensitivity of luminal B and basal BC subtypes to the NACT. The highest expression of NIS and impairment of its functional activity was registered in the group of patients with tumors resistant to NACT (stabilization of the disease or its progression) of luminal B (220 ± 8.6 points) and basal subtypes (290 ± 11.3 points) (p < 0.05). It was revealed that the disease-free survival of patients with BC of luminal B and basal subtypes was higher in the absence of NIS expression in tumor cells (p < 0.05). Conclusions: The results indicate that NIS can be used as an objective criterion for predicting the sensitivity of luminal B and basal BC subtypes to NACT, which will provide improved treatment outcomes in this group of patients.