High relative levels of satellite alpha transcripts predict increased risk of bilateral breast cancer and multiple primary cancer in patients with breast cancer and lacking BRCA‑related clinical features.

Patients with breast cancer who undergo surgery have a risk of developing multiple cancers in the contralateral breast and other organs. We previously reported that overexpression of satellite alpha transcripts (SAT) facilitates chromosomal instability, which is involved in the development of multiple tumors in patients with colorectal and gastric cancer. In this study, we elucidated the significance of SAT in the development of multiple tumors in patients with breast cancer. Relative expression of SAT (rSAT) was calculated in normal and tumor tissues from 167 patients. In total, 27 patients developed bilateral breast cancer (BBC) and 27 patients showed multiple primary cancer (MPC), with patients with BBC and MPC showing higher rSAT levels in tumor tissues than those in patients with single breast cancer (SBC) (P=0.0312 and P=0.0420, respectively). Additionally, higher rSAT levels in tumor tissues from patients with BBC were a significant factor according to univariate analysis, and multivariate analysis showed that rSAT >1.5 was a significant predictor of MPC [hazard ratio (HR): 2.96; P=0.0243); however, we did not clarify the involvement of SAT in normal tissues. Excluding 71 patients with BRCA‑related clinical features, rSAT levels were higher in patients with BBC and MPC than in patients with SBC in tumor tissues and normal tissues (P<0.05). Significant predictors according to univariate analysis included rSAT >1.5 in tumor tissues, rSAT >2.4 in normal tissues, and T <2, whereas those for multivariate analysis included rSAT >2.4 in normal tissues for BBC (HR: 22.7; P=0.00120) and MPC (HR: 13.0; P=0.00601). Our data indicated that patients with breast cancer and high rSAT levels in their breast tissues exhibit a 10‑ to 20‑fold increased risk for the development of multiple cancers when harboring no BRCA‑related clinical features.