Breast cancer is the most common diagnosed cancer in women. It’s not the most common cause of cancer death in women. That goes to lung cancer which occurs much less frequently than breast cancer but the morbidity is a great deal higher. These numbers have remained fairly stable over time. The mortality has also remained fairly stable although in some subgroups it has decreased. In women of higher socioeconomic status, more of those patients seem to be not having recurrent breast cancer or being cured, perhaps because of the effect of early detection through mammogram and education.
There are a number of risk factors that have been noted for breast cancer. The greatest risk factor is probably age and the peak incidence of breast cancer occurs between the fifth and sixth decade. If you’ve had a previous history of breast cancer in one breast, you’re certainly at increased risk to develop a second breast cancer either in the breast that’s had lumpectomy and radiation or in the other breast. Family history clearly puts you at some risk and depending on the number of members of the family that are positive and the closeness of the relationship dictates the risk. If you have a first degree relative that had bilateral premenopausal breast cancer, you probably have a lifetime risk of breast cancer that comes close to 50%.
Of course, now there are genes that we’ve identified that are inherited in an autosomal dominant way that confer lifetime risk in the 80% range and these are BRAC-1 and BRAC-2 genes. Other genes that are associated with breast cancers, P53, abnormality in the P53 gene and the ataxia telangiectasia gene that’s not been cloned.
Anything that prolongs cycling or the estrogenic cycling of the breast tissue probably is related to a slight increased risk of breast cancer. So never having a pregnancy or having a late age for first pregnancy, early menarche or late menopause all confer some increased risk for breast cancer. Prior radiation to the chest is clearly an increased risk for breast cancer particularly if it’s a lose dose radiation that occurs in the prepubertal years.