ESR1 and breast cancer: For example, in a study of 1250 HER2 positive breast cancer patients it was shown that in the ER negative subgroup of patients, obese individuals were more likely to develop distant metastases at 5 years (33.4%, 95% CI: 22.1–50.5) than those in the overweight (17.9%, 95% CI: 12.3–25.9) or under/normal weight (17.5%, 95% CI: 13.8–22.4) groups (310).