Friday, October 19, 2012

Adolescent alcohol and physical activity important for breast cancer prevention

Alcohol is a well-documented cause of breast cancer. Risk increases by approximately 7% for each 10 g of alcohol consumed daily by adult women.1-3 That is for each drink of beer wine or liquor, risk increases about 7% more compared to a never drinker. About one third of the population of US women never drinks. We have previously written on the mechanism for this increase in risk among adult women (see related posts).
Today we turn to the role of alcohol in early adult life and how it can increase risk of breast cancer by driving normal breast cell along the pathway to begin changes that are precursors or intermediate steps on the way to breast cancer. This evidence is behind our post on how parents can help lower risk for their daughters (see post Early Life and Later Breast Cancer Risk: "Hey, Mom & Dad")
First, we know that early menarche or first menstrual period, and late age at first birth, are each related to increased risk of breast cancer. In fact, during the interval between menarche and first birth the breast cells accumulate risk (or DNA damage) of progressing to cancer at a faster rate than any other time in the life of a woman. After first pregnancy, the rate of risk accumulation slows and after each subsequent birth it slows more. Finally at menopause, the rate of increase slows even more and is largely driven by circulating estrogen levels after menopause.
We have studied alcohol intake and risk of premalignant breast lesions in a number of settings and note that we see a strong increase in risk when we follow women from late adolescence into their early adult years. Alcohol intake reported in late adolescence and early adulthood increases subsequent risk of the most aggressive premalignant lesions that carry increased risk of developing invasive breast cancer.4,5
For example, our data from the follow-up of over 6000 late adolescent and young adult women and their subsequent risk of biopsy confirmed benign breast disease shows that those who have a family history of breast cancer or if their mother has a history of breast cancer – then drinking alcohol increases the risk of breast cancer precursor lesions.
Women with a family history of breast cancer who drank an average of one drink per day in late adolescence and early adult years have a doubling in their risk of biopsy confirmed benign breast disease compared to those who never drink alcohol. Given much concern among women as to what they can do to lower breast cancer risk or prevent breast cancer in their children (grandchildren, nieces, etc.) these data document that limiting alcohol intake will help avoid the increase in risk that goes with drinking 6.
During the time from menarche to first birth we might also expect lifestyle factors to lower risk – slowing the accumulation of damage to DNA in breast cells and reducing the long-term accumulation of risk of breast cancer. We, and others, have studied physical activity, or exercise, as one possible strategy to reduce risk. A number of studies now show that higher levels of activity from menarche through the premenopausal years is related to substantially lower risk of invasive breast canner.
Bernstein showed as early as 1994 that women who were active in physical exercise for 3.8 hours or more per week had half the risk for beast cancer of women who were not active at all 7. Subsequent studies confirm this protection – both in retrospective recall of activity and in prospective studies such as the Nurses’ Health Study II where women reported their activity through high school and were then followed over time to see who went on to develop breast cancer and who did not 8.
While much interest and research continues to explore how diet may modify the benefits of activity or prevent the adverse effects of alcohol in adolescence on breast cancer risk, to date the studies are few and not yet consistent enough to conclude that we can prevent breast cancer through diet in these years.  There is, however, promising evidence that higher fiber intake may reduce risk – and this is safe and recommended approach to a health diet in general 9. Likewise rowing evidence points to soy intake through childhood and adolescent years as the most protective time for this dietary factor to lower risk for beast cancer 10 11.

Related CNiC posts

Further evidence that alcohol causes breast cancer

Literature Cited

Wednesday, October 17, 2012

Early Life and Later Breast Cancer Risk: "Hey, Mom & Dad"

"Breast cancer" and "youth" are two terms not often linked together.  But there's a growing body of evidence showing that certain factors early in life - like diet, activity, and weight - can have an important impact on a woman's breast cancer risk later in life. 

To help parents guide their daughters toward optimal breast health - as well as lifelong good health - we developed the "Hey, Mom & Dad" card (below).  A high resolution file (PDF) can be downloaded: here.  A regular resolution file (PDF) can be downloaded: here.

For details on the science behind the "Hey, Mom & Dad" card, please see the slideshow "Integrating Risk Across the Lifespan: The Case of Breast Cancer Prevention" and the "Prevention Papers: Breast Cancer Prevention."

Wednesday, October 10, 2012

Breast cancer prevention

Overwhelming evidence indicates that the majority of breast cancer can be prevented with what we know now (see slide show: "Integrating Risk Across the Lifespan: The Case of Breast Cancer Prevention"). Let me review some of the justification for this statement. We know that we know from migrant studies that the rates of breast cancer vary substantially between countries and increase in the second generation after migration. We have also seen rapid changes in the rate of breast cancer within countries. For example, in Korea that the rate of breast cancer in women under 50 has doubled over a decade in large part reflecting changing reproductive patterns. Age at menarche has decreased and the number of children and age at first birth have changed to increase breast cancer risk. Later age at first birth and fewer births combine to drive up the rate of breast cancer.

We also have strong evidence from randomized trials of selective estrogen receptor modulators including tamoxifen and raloxifene where breast cancer incidence is halved. Finally in the high risk set of women with genetic predisposition through BRCA1/2 genes, surgery to remove the ovaries halves the risk of subsequent breast cancer.

Given this sort of evidence and data on other lifestyle factors that clearly modify risk, one might ask “why are we not acting to promote strategies that will prevent breast cancer now?”  A range of reasons persist, including aversion to side effects from drug therapy to reduce breast cancer.

In addition to the evidence summarized above a growing body of research points to growth and development through the adolescent and early adult years as fundamental to the level of breast cancer risk experienced throughout the rest of life. Many studies clearly document that faster growth and greater height are related to increased risk of premalignant or benign breast lesions and also invasive breast cancer. Growing evidence also points to the adverse affect of alcohol consumption during adolescent and early adult years on risk of premalignant breast lesions and on risk of breast cancer.

In addition to the adverse effect of alcohol we reported the higher fiber intake during the adolescent years is related to lower risk of subsequent premalignant breast lesions. Perhaps equally as important is the strong and consistent evidence that higher levels of physical activity from menarche through the premenopausal years substantially reducing risk of breast cancer. These lifestyle factors offer much hope for prevention of breast cancer among our daughters and granddaughters, nieces, and grand nieces. Importantly, we have shown that the benefits of these lifestyle exposures during adolescent years are present for those with a family history of breast cancer as well as those without.

Other strong evidence arguing for the importance of exposures before the adult years comes from the evidence of radiation and risk of breast cancer. Both data from atomic bomb survivors as well as follow-up studies of women who receive radiation therapy for treatment of lymphoma showed that the breast is particularly susceptible to the carcinogenic effect of radiation before age 20.

Moving forward with prevention, we must focus on more than just the individual measures of alcohol intake, physical activity, and growth. Children grow up in the broader context of society, their schools and neighborhoods. Access to safe places to be active are entwined within this societal context. If we are to achieve the prevention of breast cancer we must consider the broader social environment in which children and young adults grow to maturity. Access to healthy diet with fruits, vegetables, and higher fiber foods, adequate physical activity, and limited or no alcohol are key components of this approach. With these healthy behaviors, we can substantially reduce risk of breast cancer through the premenopausal years.

Additional resources are listed below: