In a recent report, Di Cosimo and colleagues recently reported that the combination of dalotuzumab (DALO; “MK-0646”; anti-IGF-1R antibody) and ridaforolimus (RIDA; “MK-8669”; mTOR inhibitor) had evidence of antitumor activity in estrogen receptor positive (ER+)/proliferative breast cancer patients that were refractory to multiple chemotherapy regimens. This evidence concerns the gene ESR1 and breast cancer.