BRCA2 and breast cancer: However, power was sufficient to rule out a twofold or greater increase in the odds of developing breast cancer based on one-sided 95% CIs for the following risk factors: obesity for ATM or BRCA2 carriers; smoking and alcohol for CHEK2 carriers; not breastfeeding for ATM carriers; not having oophorectomy for BRCA2 or CHEK2 carriers; not having tubal ligation for CHEK2 carriers; and NSES for carriers of PVs in any gene.