Adult Weight Gain Increases Postmenopausal Breast Cancer Risk
Posted Aug 25 2010 7:10am
As I have mentioned in several previous blogs , weight gain and obesity have been shown to increase breast cancer risk dramatically in postmenopausal women. However, little is know about whether weight gain or excess body weight effect breast cancer risk differently in different breast cancer groups. Two new studies have explored the impact of body weight on (1) breast cancer hormone receptor status and (2) breast cancer risk in BRCA1/2 mutation carriers.
In the first of these two new breast cancer studies, breast cancer researchers conducted an analysis of several research papers to determine if weight gain differentially effected breast cancer risk in breast cancers with different hormone receptor characteristics. According to this study, the combined risk for estrogen receptor positive (ER+) breast cancers and ER+/progesterone receptor positive (PR+) breast cancers was doubled in postmenopausal women with the highest category of weight gain compared to postmenopausal women with the least weight gain. The risk for ER-/PR- breast cancers was increased by 33% for postmenopausal women with the highest level of adult weight gain. No links were observed between adult weight gain and the risk of ER+/PR- breast cancer tumors. This study indicates that adult weight gain was linked to both ER-/PR- and ER+/PR+ breast cancers; however, breast cancer risk was substantially greater for ER+/PR+ breast cancers compared to ER-/PR- breast cancers.
In the second breast cancer research study, investigators examined the possible impact of obesity on breast cancer risk in BRCA1/2 mutation carriers . Information on body weight, height, body mass index and breast cancer were collected by questionnaire in a nationwide study that included over 700 BRCA1/2 carriers, over 200 of whom developed breast cancer. The following relationships were observed in postmenopausal women carrying the BRCA1/2 mutations
Being taller than 5'6" increased breast cancer risk by about 1.7-fold when compared to being shorter.
A current body weight of more than about 159 lbs doubled breast cancer risk.
Being overweight (BMI of 25 or higher) increased breast cancer risk by 46%
Gaining more than about 10 lbs as an adult or experiencing a 20% weight gain as an adult were linked to about a 60% increased breast cancer risk.
However, in this study, the breast cancer researchers observed no association between body weight/BMI and premenopausal breast cancer risk. This second study suggests that postmenopausal women carrying either the BRCA1 or BRCA2 gene mutation might still be able to decrease their risk for developing breast cancer by maintaining a healthy body weight throughout their lives.
Overall, these two new breast cancer studies add to the growing amount of evidence that adult weight gain and obesity are major risk factors for postmenopausal breast cancer. These studies also point out that the increased breast cancer risk linked to obesity and weight gain might impact breast cancer characteristics. Maintaining a healthy body weight throughout life, while not always easy, remains an achievable lifestyle modification that can reduce one's breast cancer risk.