You may have read the sensational headlines covering a recent Johns Hopkins study on cancer: Two Thirds of cancers are due to ‘bad luck’. Some people with cancer take comfort in this concept, feeling better knowing that there was nothing in particular they did or didn’t do that caused their cancer. But in general, humans seek explanation and most people, when they are told they have cancer want to know why, “why me…what caused this?” And I think most people who do not have cancer are uncomfortable with the thought of some purposeless, unpredictable, uncontrollable cancer force out there that can shape one’s destiny. We want to be able to do something.

The headlines succeeded in getting lots of attention, including mine. But, then I quickly realized the headlines are just flipping a statistic that Rethink Breast Cancer and other breast cancer organizations have been pushing hard the past couple of years: two thirds might be luck, but that leaves one third of breast cancers preventable through making healthy lifestyle choices.

And behind the headlines, the Johns Hopkins study that sparked them tells a more complex story about cancer and-so called ‘bad luck’. (Note: the study looked at 31 different types of tissues but did not look at tissue from breast and prostate cancers). The study’s researchers wanted to understand why lifetime cancer risk varies so much in different parts of the body. In other words, why are we so much more prone to get one type of cancer versus another type? Why are certain organs or body parts more susceptible to cancer? The scientists at Johns Hopkins reviewed the literature on the number of stem cell divisions among 31 tissue types, estimating the number of times an individual’s stem cells divide over a lifetime. They plotted the total number of times the tissue cells divide and compared those rates with the average lifetime risk for cancer in those tissue types, looking for a correlation between the two. They discovered a significant link between the number of stem cell divisions and the lifetime risk of cancer across a range of types of cancers. Through their calculations, they concluded that 65% of the differences in cancer risk across tissue types were explained by the number of cell divisions in those tissues. Those parts that have higher lifetime cell division carry an increased cancer risk due to more opportunities for there to be a random error in DNA replication. It is these random errors which are being called ‘bad luck’.

And what about breast cancer?

Breast tissue was not looked at in the Johns Hopkins study because the scientists conducting the research could not find accurate information about the stems cell division rate. Even though breast cancer was not a focus of this study, the research findings and the media articles covering those findings impact our community. It’s important to clear the confusion some may be feeling and re-iterate what we do know about breast cancer and risk. We know that only about 5 to 10% of breast cancers are due to inherited genetic defects. We also know that the main risk factors for getting breast cancer are being a woman and getting older. For the majority of women, there is no explanation for why they got breast cancer beyond an error in cell replication (which becomes more likely as you age) that leads to a cancerous growth – aka ‘bad luck’. However, we also know that there are ways to reduce the risk of breast cancer by nearly a third by making lifestyle changes that are also good for your overall health and reducing the risk of other cancers and diseases.

The 5 main risk reductions tips are:

  1. Exercise regularly
  2. Limit the amount of alcohol you drink
  3. Quit smoking
  4. Eat a diet high in fibre and plant based foods and low in processed foods
  5. Maintain a healthy weight, especially after menopause (number 1 and 4 help with this)

We know the issue of cancer prevention is a complicated one, with new research and findings constantly being thrown into the mix. We also know there will be women who follow all of the above tips and will still unfortunately be diagnosed with breast cancer (due to ‘bad luck’). But leading a healthy lifestyle is always a smart idea, and although there are no guarantees, you can improve your odds of living a cancer free life. To paraphrase the common sports analogy, “you’ve got to be good to be lucky.” So don’t leave your health to fate – be proactive about your health and reduce your risk.

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