Innovation path to sustainable world - breast cancer prevention

I had the privilege of presenting in this thematic area for the Shanghai Forum and addressed the priority for prevention. This contrasted with a preceding talk that advocated for greater emphasis on genomic testing to focus prevention activities within the Chinese population. Using diabetes and breast cancer examples I contrasted the time course of disease development and the importance of acting now with our current information, particularly given the dramatic changes in diet and physical activity among children in China over the past 25 years. Needless to say, diet has moved to more western pattern increasing risk of diabetes and cancer, physical activity has declined.

The immediacy of providing health services makes demands on health systems that draw the focus away from using the knowledge we already have. Lets look at the evidence on breast cancer as an example of why we need to act quickly to reduce the global burden. Already, breast cancer is the number 1 cancer diagnosis among women in the world. In 2012, 1.7 million women were diagnosed with breast cancer (25% of all new cancer cases).

In Asia the incidence rate of breast cancer in women under age 50 continues to rise. For example, data from the shanghai tumor registry included in the IARD report on cancer are summarized below.

	35-39	40-44	45-49
1998-2002	32.0	76.5	104.4
1993-1997	35.6	60.6	86.9
1988-1992	31.5	61.1	81.5

This is no surprise because age at first menstrual period has fallen from an average of 16 or 17 for women born in 1930 to 14 for women born in 1970 ¹ and down to 12 for women born in Beijing by 1990 (menarche assessed through 2004). This age at menarche is slightly younger in cities and a little older for those in rural settings.

Figure 1. Age at menarche by year of birth for women in China from Lewington et al IJE 2014.

The number of children has plummeted throughout the world. Although the number of babies born continues to rise to a possible record of 136 million babies in 2007 (May 23, 2014: http://www.worldwatch.org/node/5645). This is explained by the number of women between age 15 and 49, which has double in the past 435years, to 1.7 billion. Thus, even with fewer babies born for each women, the total births rise and global population is projected to pass beyond 9 billion, stressing our ability to feed and provide health services for all.

Back to number of children… in China up to 1950 women had an average of 5 babies (urban) or 6 children (in rural settings) - see figure 2, ale drawing on Lewington et al IJE 2014. 

The age a women has her first baby has increased from 19 in 1950 to 25 or more in 1995.

Children historically were spaced about 3 years apart and this has increased in the recent past of those who have more than 1 child.

Based on one survey of several hundred thousand women, …

As a society or civilization, we have effectively extended the interval from first menstrual period to first birth from about 2 years to almost 18. This given an increase in the number of menstrual periods on average before first birth from say fewer than 26 menstrual periods; to some 234 cycles (18yrs x13 cycles/year), before the full cellular differentiation that accompanies breast development during first pregnancy; this is an increase of more than 200 cycles. Furthermore, it represents almost 18 more years of breast risk accumulation before the protection of first pregnancy. Lifestyle during this time of life determines life long risk of breast cancer.

Using our validated model of breast cancer incidence ^2,3 we know that, if a woman has a first baby at 19 and has the weight and height of average women in China born 1925 to 1978 ⁴ then at age 50 she would have an incidence rate of about 50 cases per 100,000 women. In contrast the current incidence in the USA is 182 cases per 100,000 women (SEER data).

If, however, we apply the new normal, menarche at 12, first birth at 27, and only 1 birth (consistent with China and Korea today) then we expect an incidence of about 147 cases per 100,000 women at age 50. The current incidence in Korea closely reflects these numbers, as do data from Shanghai. Shifting patterns of reproductive characteristics of women in a population dramatically change breast cancer incidence.

So what are we ignoring?

Strong evidence supports higher intake of vegetables in the diet are related to lower risk of breast cancer. Soy intake in childhood and adolescence is related to lower risk ^5-7, as is higher fiber intake ⁸ and higher vegetable protein intake ^8-10. Yet, China has had a hugged drop in consumption of vegetable sources in the diet and greatly increased intake of animal sources. The data from the China National Health Survey for children 2 to 18 years of age are summarized in the figure. We note a 50% increase in animal sources and a 70% decrease in course fiber sources in the diet over the 120 years form 1991 to 2011 ¹¹.

Physical activity in adolescence is directly related to lower risk of breast cancer ^12,13 – yet we see continuing trends with industrialization to lower physical activity. Driven largely by a drop in occupational activity women in china have decreased their overall activity by about 50% from 1991 to 2011 ¹⁴.

These dietary changes and reductions in physical activity will combine to exacerbate the increase in risk driven by changing reproductive patterns.

Of course, with higher education we see women drinking more alcohol.

In China, for example, women without high school education report abstaining from alcohol. Based on data from 500,000 men and women enrolled in the China Kadoorie Biobank cohort study born 1925 to 1978; overall 63% of women reported never drinking alcohol ¹⁵.  When stratified by education alcohol consumption increased with level of education. Among women with no formal education 71% never drank alcohol, while for women with college or university education, 47.8 % never drank. Alcohol a known breast carcinogen is increasing and will add further to the burden of breast cancer. Importantly, intake between first menstrual period and first birth drives risk of premalignant and invasive breast lesions ^16,17.

Recommendations

While the world health organization recommends not smoking, eating a healthy diet, being physically active, and limiting alcohol intake, the importance of age is ignored^18.  For beast cancer, the leading cancer burden among women in the world, we must refocus on the critical period before age 30 when breast cells are most susceptible to risk and lifetime risk is set.

If we act and act now, supported by additional resources devoted to implementing prevention, bringing messages and sustaining lifestyle and risk reduction strategies during the critical time points in life, we can achieve a world-wide turn around overcoming outrage. The burden of the leading cancer diagnosed in women can decrease now and for future generations.

Literature cited

1.         Lewington S, Li L, Murugasen S, et al. Temporal trends of main reproductive characteristics in ten urban and rural regions of China: the China Kadoorie Biobank study of 300 000 women. Int J Epidemiol. Mar 17 2014.

2.         Rosner BA, Colditz GA, Hankinson SE, Sullivan-Halley J, Lacey JV, Jr., Bernstein L. Validation of Rosner-Colditz breast cancer incidence model using an independent data set, the California Teachers Study. Breast cancer research and treatment. Nov 2013;142(1):187-202.

3.         Colditz GA, Rosner B. Cumulative risk of breast cancer to age 70 years according to risk factor status: data from the Nurses' Health Study. American journal of epidemiology. Nov 15 2000;152(10):950-964.

4.         Chen Z, Chen J, Collins R, et al. China Kadoorie Biobank of 0.5 million people: survey methods, baseline characteristics and long-term follow-up. Int J Epidemiol. Dec 2011;40(6):1652-1666.

5.         Wu AH, Yu MC, Tseng CC, Pike MC. Epidemiology of soy exposures and breast cancer risk. Br J Cancer. Jan 15 2008;98(1):9-14.

6.         Korde LA, Wu AH, Fears T, et al. Childhood soy intake and breast cancer risk in Asian American women. Cancer Epidemiol Biomarkers Prev. Apr 2009;18(4):1050-1059.

7.         Yang G, Shu XO, Li H, et al. Prospective cohort study of soy food intake and colorectal cancer risk in women. Am J Clin Nutr. Feb 2009;89(2):577-583.

8.         Liu Y, Colditz GA, Cotterchio M, Boucher BA, Kreiger N. Adolescent dietary fiber, vegetable fat, vegetable protein, and nut intakes and breast cancer risk. Breast cancer research and treatment. Apr 16 2014.

9.         Berkey CS, Willett WC, Tamimi RM, Rosner B, Frazier AL, Colditz GA. Vegetable protein and vegetable fat intakes in pre-adolescent and adolescent girls, and risk for benign breast disease in young women. Breast cancer research and treatment. Sep 2013;141(2):299-306.

10.       Su X, Tamimi RM, Collins LC, et al. Intake of fiber and nuts during adolescence and incidence of proliferative benign breast disease. Cancer causes & control : CCC. Jul 2010;21(7):1033-1046.

11.       Zhai FY, Du SF, Wang ZH, Zhang JG, Du WW, Popkin BM. Dynamics of the Chinese diet and the role of urbanicity, 1991-2011. Obes Rev. Jan 2014;15 Suppl 1:16-26.

12.       Bernstein L, Henderson BE, Hanisch R, Sullivan-Halley J, Ross RK. Physical exercise and reduced risk of breast cancer in young women. J Natl Cancer Inst. 1994;86:1403-1408.

13.       Maruti SS, Willett WC, Feskanich D, Rosner B, Colditz GA. A prospective study of age-specific physical activity and premenopausal breast cancer. Journal of the National Cancer Institute. May 21 2008;100(10):728-737.

14.       Ng SW, Howard AG, Wang HJ, Su C, Zhang B. The physical activity transition among adults in China: 1991-2011. Obes Rev. Jan 2014;15 Suppl 1:27-36.

15.       Millwood IY, Li L, Smith M, et al. Alcohol consumption in 0.5 million people from 10 diverse regions of China: prevalence, patterns and socio-demographic and health-related correlates. Int J Epidemiol. Jun 2013;42(3):816-827.

16.       Liu Y, Tamimi RM, Berkey CS, et al. Intakes of alcohol and folate during adolescence and risk of proliferative benign breast disease. Pediatrics. May 2012;129(5):e1192-1198.

17.       Liu Y, Colditz GA, Rosner B, et al. Alcohol intake between menarche and first pregnancy: a prospective study of breast cancer risk. Journal of the National Cancer Institute. Oct 16 2013;105(20):1571-1578.

18.       World Health Organization. Global Action Plan for Prevention and Control of Noncommunicable Diseases, 2013-2020. http://www.who.int/cardiovascular_diseases/15March2013UpdatedRevisedDraftActionPlan.pdf: World Health Organization,; MArch 15, 2013 2013.

The 8IGHT WAYS Guide to Preventing Breast Cancer (Excerpt): What is Risk? What is Prevention?

An excerpt from the upcoming e-book: The 8IGHT WAYS Guide to Preventing Breast Cancer (Colditz and Dart)

What is Risk? What is Prevention? 

The word “risk” gets thrown around a lot these days.  And that’s actually a great thing, particularly when it comes to breast cancer.  By knowing your risk of breast cancer, and what factors make up that risk, you can make better informed decisions not only about your breast health but how you choose to mentally and emotionally deal with the issues of breast health and breast cancer. 

In technical – and very dry – terms, the risk of a disease is the chance of getting that disease over a certain period of time.  The most common timeframes used to describe risk are 10-year increments and something called “lifetime risk” – the chance of ever developing the disease as an adult. 

When it comes to breast cancer, lifetime risk is the one most women would recognize by the ratio “one in eight.”   “One in eight” describes an average American woman’s lifetime risk of ever developing breast cancer, meaning that out of every 8 women, 1 will develop the disease.  This translates to about a 12 percent chance of being diagnosed with breast cancer from age 18 until about age 85.

Compared to many other health risks, this is a pretty high percentage, but certainly not the highest for a major disease.  The lifetime risk of heart disease, say, is about 50 percent. 

Not surprisingly, looking at breast cancer risk in shorter 10-year segments can make things look less daunting – and in some ways provides a better sense of actual risk. Because diseases like cancer and heart disease are more common as women age – and to be blunt, because everyone eventually dies of something – lifetime risks can easily inflate the perception that a disease is more threatening than it actually is.  This is because so much of the risk accumulates very late in life.  

For some perspective, let’s look at the risks of breast cancer across a couple ten-year age groups:  the average woman’s risk of developing breast cancer from age 40 to age 50 is 1.5 percent, and from age 60 to 70 is 3.5 percent (1). This means that out of a 100 forty year old women, 1.5 would develop breast cancer by the time they turned 50.  Likewise, out of 100 fifty year old women, 3.5 would develop breast cancer by the time they turned 60.  (Of course, these are statistical “people” since you can’t have half a person.).

As expected, these 10-year risks are much smaller than the average lifetime risk of 12 percent.  Though they still show breast cancer to be a prominent disease – these risks are about three times higher than those of colon cancer for the same age groups – they also show that breast cancer is not as imminent a threat as many women fear.  It’s not uncommon for younger women to overestimate their risk of dying from the disease over the next 10 years by up to 20 times (2).

Many factors determine a woman’s risk of breast cancer, including things she has control over, like exercise and diet, and things she has little or no control over, like genetics and family history.   Focusing efforts on those factors that can be changed for the better can lower the risk of breast cancer. 

In other words, it can help prevent it. 

An Ounce (or More) of Prevention

Prevention has become a real buzzword of late, and that makes many a health professional jump for joy.  Why?  Well, let’s look at the classic “river story” parable, which we’ll paraphrase. 

A woman was walking on a riverbank and saw someone floating down the river yelling for help.  The woman picked up a large tree branch and fished the person out.  No sooner did she do that then another person came floating down.  She fished that person out.  Then another and another and another came down.  She asked others to help rescue the people. And they did.  Still, more and more came floating down, and the helpers were soon overwhelmed, realizing they couldn’t help everyone. 

The woman decided to quickly run up-river to see why so many people were falling in.  On a popular bridge over the river, she found a large, obscured hole that people were falling through.  She patched it, and people no longer fell into the river through the hole.

This story perfectly illustrates the power of prevention.  By working to stop problems early on, you can help avoid bigger, harder issues later on.  We’ll never be able to stop all the people from falling into the river.  But repairing as many holes as we’re able to can help cut way down on the number of people who fall in and need heroic rescue downstream.

It’s the same way with diseases like cancer and heart disease.  A healthy lifestyle can cut down on the number of people who develop a disease.  And although we’ll likely never be able to stop 100 percent of cancers or heart attacks, prevention still offers the most realistic, efficient, and effective way of tackling the burden of chronic diseases the world over.

References

1.         Howlader N, Noone AM, Krapcho M, Garshell J, Neyman N, Altekruse SF, Kosary CL, Yu M, Ruhl J, Tatalovich Z, Cho H, Mariotto A, Lewis DR, Chen HS, Feuer EJ, C. KA. (National Cancer Institute, Bethesda, MD, 2013).

2.         W. C. Black, R. F. Nease, Jr., A. N. Tosteson, Perceptions of breast cancer risk and screening effectiveness in women younger than 50 years of age. J Natl Cancer Inst 87, 720-731 (1995); published online EpubMay 17

Letter to the Editor on Diet and Cancer: "No Myth"

Photo: Flickr/ToastyTreat

As we mentioned in a previous post on CNiC, an article in the New York Times last week called the link between diet and cancer risk, in essence, a "myth."  In that post, we note that "the article's conclusions [about the links between diet and cancer] demonstrate a lack of understanding of the science."  To further make that point - and address a couple others - we also responded with a letter to the editor of the New York Times, printed below. 

April 21, 2014 

letters@nytimes.com 

To the Editor: 

Re: “An Apple a Day, and Other Myths.” 

There are strong links between the foods we eat and our cancer risk – for the author, George Johnson, to conclude otherwise is an incorrect interpretation of evidence that sends the wrong message at a critical time in the health of the nation.  

Cancer will become the top cause of death in the United States within the next few years, and despite hopes to the contrary, it is very unlikely that advances in diagnosis and treatment will have a major impact on the burden of the disease in the foreseeable future.  Yet, today, strong evidence shows that 50 percent or more of all cancers is preventable with relatively simple behaviors – including eating a healthy diet. 

Good studies show that too much alcohol, red meat, and processed meat as well as inadequate fruits, vegetables, and folate (found in many plant foods) have important links to cancer risk or mortality.  And other associations are developing.   

We need to do all that we can to address the growing burden of cancer.  A healthy diet is one established way to do that, and that is no myth. 

Graham A. Colditz, MD, DrPH

Setting the Record Straight: The Impact of Diet on Cancer Risk

Photo: Flickr/Mike65444

An article posted earlier this week on the New York Times website stated that the link between diet and cancer risk was, in essence, a "myth."  And while links between diet and cancer are not as strong as those with some other chronic diseases, like heart disease, the article's conclusions demonstrate a lack of understanding of the science.

Yesterday, the American Institute for Cancer Research (AICR) - whose reports were referenced in the piece - posted their own response to the article detailing many links between diet and cancer, with AICR Director of Research, Susan Higginbotham, PhD, RD, stating: "If there’s one thing AICR’s research has shown, and continues to show, it’s that when it comes to cancer risk, diet does matter.”

As detailed in many of our scientific publications, consumer brochures, and risk assessment tools, we agree. Diet has an important impact on cancer risk.  Calories alone, and the weight gain they can cause, can impact at least 11 different cancers.  Too much alcohol is a key risk factor for colon and breast cancer - even at moderate levels of intake.  Fruits and vegetables can lower the risk of certain types of breast cancer.  Too much red meat - particularly processed meats - can substantially increase colon cancer risk.  Adequate calcium and vitamin D can lower colon cancer risk. And inadequate folate (a B vitamin found in many plant foods) has been linked to overall cancer mortality.  Strong associations with other dietary risk factors are quickly developing.

The message that cancer is a disease that can be prevented is extremely important.  It is also a message that is still just gaining momentum with both physicians and the public.  To greatly downplay the potential impact of diet on cancer risk is not true to the science and can lead to important missed opportunities for prevention.

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Prevention Resources

Our 8IGHT WAYS® series is filled with great tips for improving your health and lowering cancer risk.

8IGHT WAYS to Stay Healthy and Prevent Cancer  

8IGHT WAYS to Prevent Breast Cancer 

8IGHT WAYS to Prevent Colon Cancer 

CANCER SURVIVORS' 8IGHT WAYS to Stay Healthy After Cancer

Our popular risk assessment tools are also great resources for learning about your risk and getting personalized prevention plans.

Your Disease Risk website 

Zuum - Health Tracker app for iPad