The Role of Long Non-Coding RNAs in Breast Cancer Diagnosis and Treatment Based on Evidence from Clinical Studies: A Scoping Review

Background/Objectives: The aim of this scoping review was to investigate the current role and possible clinical applications of long non-coding RNAs (lncRNAs) in breast cancer diagnosis and treatment. Methods: A thorough search of the PubMed/MEDLINE and Scopus/EMBASE databases was carried out in accordance with the PRISMA-ScR guidelines. The inclusion criteria were as follows: Studies with lncRNA analyses of specimens from breast cancer patients and clinically relevant studies. The exclusion criteria were as follows: in silico and in vitro studies involving animal models; reviews; case series; case reports; comments; editorials; and papers not written in English. The study protocol was registered in the Open Science Framework. Results: After the identification of 1139 records, 312 publications were retrieved and 228 articles were selected for data extraction. Data analysis and the synthesis of evidence showed that lncRNA studies were conducted in breast tumor specimens in 212 studies and in blood samples from breast cancer patients in 20 studies. The most commonly used method was quantitative RT-PCR (in 216 studies), while many studies were complemented by in vitro (n = 177) and animal experiments (n = 75). There were 39 studies that included at least 100 specimens from breast cancer patients. Conclusions: At present, lncRNA analysis is not used in routine clinical practice. Clinically relevant findings coupled by results from in vitro and animal experiments suggest that various lncRNAs after appropriate validation may be used as biomarkers for breast cancer diagnosis and treatment, most notably HSAT164, CCAT2, HOTAIR, and MALAT1. To this end, larger studies involving clinical specimens from clinically relevant subgroups of breast cancer patients will be needed.