Don’t assume you can know who will benefit and who will be harmed by a health action.
The effects of things we do for our health (health actions) vary from person to person. It is rarely possible to know in advance precisely who will benefit and who will not from doing something for their health.
Explanation
Usually, in a group of people who have taken a health action, some people benefit, some do not benefit, and some may be harmed. It is rarely possible to know in advance who will benefit and who will not. A fair comparison of health actions can tell us what happened in a group of people who took the action compared to another group of similar people who did not. But fair comparisons don’t tell us who will benefit and who will not if they take the same health action. Sometimes, fair comparisons are used to identify which types of people are most likely to benefit from a specific health action. This information may then be used to customize health actions for individual people (for example, people who have a particular characteristic or gene). This is sometimes called ‘personalised medicine’ or ‘precision medicine’. It is important to remember that even in personalised medicine, it is still not possible to know for sure who will benefit and who will not, or even be harmed.
Example
HER2-positive breast cancer is a type of breast cancer in which the cells have a special part called a HER2 protein receptor. Only about 20% of breast cancers are HER2-positive. Medicines that block HER2 receptors to keep cancer cells from growing (e.g., Herceptin) are used to treat HER2-positive breast cancer. So, those medicines are given to women with HER2-positive breast cancer and not to other women with breast cancer. However, not all women with HER2-positive breast cancer benefit from the medicine and some will experience serious harmful effects, such as heart failure. It is not possible to know in advance which women will benefit or which will be harmed.
Remember: There is almost always some uncertainty about who will benefit, who will not, and who will be harmed by taking a health action.
- Article: The Overhyping of Precision Medicine, Science has a history of inflated promises when it comes to disease treatment. The Atlantic.
- Blog: Precision medicine: Hype over hope? Respectful Insolence.