ESR1 and breast cancer: In the California Teachers Study (CTS), taking 3 or more tablets per week of low-dose aspirin (but not regular strength aspirin) was associated with a reduced risk of breast cancer overall, and especially for the ER+/HER2− subtype (HR 0.80; 95% CI 0.66, 0.96) with no association for ER− breast cancer [16]; however, a prior analysis within the CTS showed a statistically significant increased risk of ER− breast cancer associated with daily, long-term use of aspirin (unspecified dose) [17].