ADRB2 and breast cancer: β2-Adrenergic receptor (β2-AR) antagonists, including nonselective β-blockers (nsBBs) that block both β1- and β2-AR, have been found to inhibit these effects in several preclinical models.13,17,18,19 This inhibition has not been demonstrated to the same extent for selective BBs (sBBs), which target only β1-ARs.18 In a randomized clinical trial20 in patients undergoing mastectomy for breast cancer, perioperative treatment with the nsBB propranolol reduced biomarkers associated with metastasis.