Everolimus was the first approved mTOR inhibitor for HR+/HER2− breast cancer and showed an improved PFS in several clinical trials (Bachelot et al., 2012; Yardley et al., 2013), whereas another mTOR inhibitor, temsirolimus, showed only moderate activity in HR+ breast cancer patients with age ≤ 65 years, but this randomized phase III trial was terminated for futility as total PFS was not improved by temsirolimus plus letrozole as first-line therapy, so the best suitable population for temsirolimus needs to be further identified (Wolff et al., 2013). This evidence concerns the gene MTOR and breast carcinoma.