It is rarely possible to know in advance who will benefit, who will not, and who will be harmed by using a treatment.
Fair comparisons of treatments usually tell us what happened in a group of people. There are very few, if any treatments that have exactly the same effect on everyone. Usually, in a group of people that use a treatment, there are some who benefit, some who do not, and some who are harmed by the treatment. When you use a treatment, it is not possible to know in advance if you will be one of the people who benefits, one of the people who does not benefit, or one of the people who is harmed.
The only way to know whether “personalised medicine”- tailoring treatment for individuals – works is to test it in fair comparisons. Unless the tailored treatment is 100% effective and 100% safe, it is still not possible to know in advance exactly who will benefit from “personalised care” and who will not. “Personalised medicine” is not really tailored for each individual; it is simply an effort to identify those people who are most likely to benefit from specific treatments.
BEWARE of claims about “personalised medicine” that have not been evaluated in fair comparisons.
REMEMBER: It is rarely possible to know in advance who will benefit, who will not, and who will be harmed by using a treatment.