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Cancer Prevention and Screening

In June 2008, our guest expert in Le Club's Ask the Expert segment was Dr. Christine Friedenreich, a cancer epidemiologist and research scientist with the Division of Population Health of the Alberta Cancer Board (ACB).

Dr. Friedenreich studies patterns of disease in populations, and has spent much of her career identifying modifiable risk factors for cancer.

She is an adjunct professor in the Faculties of Medicine and Kinesiology of the University of Calgary (U of C), and holds a career award from the Alberta Heritage Foundation for Medical Research.

Dr Friedenreich completed her doctorate in Epidemiology at the University of Toronto in 1990, and postdoctoral work at the International Agency for Research on Cancer (IARC) in Lyon, France and at the U of C between 1990 and 1994.

Her current research is focused on understanding the role of physical activity in reducing the risk of developing cancer, and in improving quality of life and survival after a cancer diagnosis.

Here are Dr. Friedenreich’s answers to your questions on Cancer Prevention and Screening:

Q: My mother died in 1979 from metastasized colon cancer, so now I have a cancer phobia. Other than psychiatric counselling, how can I protect myself from stomach, liver, pancreas, spleen and kidney cancer?  I already know about preventing colon and skin cancers...just not the rest.

A: The best approach for reducing cancer risk is to follow the guidelines established by the Canadian Cancer Society which include not smoking, being physically active, maintaining a healthy weight, eating a balanced diet that is rich in fruits and vegetables and low in red meat, limiting alcohol intake and sun exposure.

These guidelines apply to all cancer sites. For more information on these lifestyle factors, please read the American Institute for Cancer Research/World Cancer Research Fund's report on Food, Nutrition and Physical Activity for Cancer Prevention that was released in November 2007. This comprehensive review of over 7,000 studies conducted worldwide provides site-specific recommendations that you may find useful.


Q: I was diagnosed with a rare skin cancer a few years ago: mycosis fungoides (cutaneous t-cell lymphoma). I had treatment for it and it is currently 'under control' meaning it is NOT active. But as I have been told, I still have it, and will always have it. Are there certain supplements or foods I should increase in my diet to keep the cancer at bay, so to speak?

I guess what I am asking is, are there some foods that help fight cancer, and is boosting the immune system what I should be concentrating on?

A: The best approach for any cancer is to eat a balanced diet rich in fruits and vegetables, low in red meat and alcohol. There are no known supplements that can be taken to boost the immune system that should be concentrated on specifically.


How can a woman prevent and eliminate calcification in breast tissue?

A: There is nothing that a woman can do to prevent and eliminate calcification in breast tissue. The main risk reducing strategy for breast cancer is to be physically active by exercising for at least 30 minutes per day for at least five days per week.


Q: Is it possible to predetermine if a woman will get cancer by 'making a link' with the wax that she produces in the ears?

A: The association between ear wax and breast cancer risk has not been sufficiently studied to make any kind of statement regarding causality. At least 20 studies need to be conducted on a topic using different populations from around the world, different study designs and that demonstrate a strong effect with evidence for a dose-response and some underlying biologic plausibility. At present, none of these criteria for causality have been met for ear wax and breast cancer.


Q: I would like to know if asymmetrical breasts (one breast smaller than the other) can develop cancer.  Is this abnormal?  Is it possible to correct this with surgery and have normal symmetrical breasts? Thank you very much.

A: All women have breasts that are not perfectly symmetrical or even the same size. Hence, it is not abnormal, nor does it increase breast cancer risk, and hence no surgery is required to correct the asymmetry with respect to breast cancer risk reduction.


I live in downtown Toronto, and tend to walk everywhere. I applaud the fact that there is no smoking allowed in bars and restaurants. Unfortunately, I find that just by walking along the city streets I am fighting my way through clouds of smoke every day, because there are so many smokers outside in doorways. Sometimes I get home and can actually smell cigarettes in my hair. Add to that the smog and exhaust fumes I am taking in just by living here. My question: Is this kind of exposure significantly increasing my risk of lung cancer, or other types? What can I do to protect myself? Should I think seriously about moving to the suburbs, or even a smaller city? Thank you.

A: It is unlikely that being exposed to air pollution by living in an urban centre is increasing your risk of lung cancer or other cancer types, however, these types of associations have not been well studied given the difficulty in measuring exposure to air pollution in a population-based study.

If you have the ability to move to another setting with lower air pollution and wish to do it for other reasons besides your cancer risk, then, you can certainly do so. However, such a move would not be warranted based solely on your desire to reduce your risk of lung cancer. Maintaining a healthy diet with lots of fruits and vegetables, being physically active and not smoking are the main lifestyle changes you can make to reduce your lung cancer risk.


Q: Is there more that I could be doing to prevent cancer from returning? I am 64 and have been taking Arimidex since September 2007 after breast cancer. I have been eating healthy, walking a half hour a day and keeping an optimistic attitude. I am still in recovery mode after having chemotherapy, surgery and radiation, ending in January 2008. I want so very much to return to my old healthy self as quickly as possible and remain that way.

A: Congratulations! You are already doing most of what has been shown to reduce a recurrence of breast cancer. In addition to a healthy diet and regular exercise, ensure that you maintain your weight in a healthy range (body mass index or BMI at less than 25). Keep up the positive attitude, and you will soon be feeling much better once you have overcome the effects of your treatments.


Q: I've heard a lot about environmental causes of cancer, but I've also heard that environmental cause and effect can't always be proven without a doubt. If that's true, could you comment on why that is? And how can I assess all these news stories I hear so that I can make the best choices to avoid cancer, without becoming completely obsessed?

A: There are several environmental causes of cancer that are clearly understood including lifestyle factors such as diet, exercise, smoking, sun exposure and weight gain that can be controlled by an individual. Other environmental factors, such as air, water and soil contamination with chemicals have also been extensively studied and classified by the International Agency for Research on Cancer (part of the World Health Organization). These classifications signify how strong the evidence is regarding whether or not these exposures are carcinogens.

For many occupational exposures (i.e. exposures that occur in the workplace), much better controls have been established to ensure that these exposures are kept to a minimum. For other environmental and occupational exposures, the evidence is not yet well established because either the research has not been done or the research has shown inconclusive results. For these factors, more research is needed.

In this field, it is quite difficult to definitely determine causality since a number of criteria need to be met including the strength of the association (how much is the risk increased), the temporal association (did the exposure occur before the disease onset), the consistency of the association (do the same results occur if the study is repeated in several different places around the world using different populations and study designs), the biologic plausibility (does the association make biologic sense) to name just a few. For many environmental exposures, we only know that there may be some kind of association.

The best approach for an individual is to focus on the factors that are modifiable and for which personal control exists. These factors include lifestyle choices such as smoking, alcohol use, dietary intake and physical activity. All of these factors have been clearly shown to be associated with cancer risk and by modifying these exposures, personal risk of cancer can be decreased by nearly 50 percent. Hence, do not become obsessed with possible environmental exposures since the risks with most of these exposures are much lower than for the lifestyle ones just listed (particularly for smoking).

Q: I will be 53 in August and I do not have any children.  What is the single most important advice you can give me to prevent cancer – especially breast cancer?

A: As a woman who is likely perimenopausal or menopausal, your risk of breast cancer increases as you age. Hence, the most important means of decreasing your risk of this cancer is to stay physically active and maintain a healthy body weight (below a BMI of 25) throughout your life. Even if you have been inactive before menopause, you can reduce your breast cancer risk after menopause significantly by being physically active.


Q: Is a macrobiotic diet and life style helpful in terms of cancer prevention?

A: Being physically active, eating a balanced diet that is rich in fruits and vegetables, minimizes red meat and alcohol intake, not smoking, reducing sun exposure and maintaining a healthy weight throughout lifetime are all excellent means for reducing cancer risk.


Q: What are the best prevention methods and screening tests for ovarian cancer?

A: Currently there are no screening tests for ovarian cancer but this is an area of active research effort. The best prevention for ovarian cancer is to maintain a healthy weight by staying physically active and eating a balanced diet.


Q: At what age should a woman begin breast cancer screening and colorectal cancer screening if family history is not known?

A: In Canada, the current recommendations for both breast and colorectal cancer screening are to begin at age 50 when no family history of these cancers exists or is unknown.


Q: Where can I find a complete list of all suspected carcinogens in North America and Europe? 

A: The International Agency for Research on Cancer (World Health Organization) maintains a listing of all the suspected carcinogens in the world. 


Q: Recent news had a story about a research study that showed that bariatric surgery lowered people's risk of cancer. What does this mean? Is it simply that someone who is no longer obese no longer has that co-morbidity factor of obesity and other diseases such as cancer? Or is something else at play here?

A: Having not read this study, I cannot comment directly about that study, however, bariatric surgery would reduce obesity which has been clearly shown to increase the risk of several different types of cancer. By maintaining a healthy weight, cancer risk is reduced.


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