ESR1 and neoplasm: The primary analyses show that the SUVmax is significantly higher in ER-negative (SMD 0.66, P < 0.0001), PR-negative (SMD 0.56, P < 0.0001), HER2-positive (SMD − 0.29, P = 0.0043) or Ki-67-positive (SMD − 0.77, P < 0.0001) primary tumours compared to their counterparts.