Effective, Yes, but Is It Safe? A Drug’s Risks

.....But reliable surrogates are hard to find. There are plenty of endpoints that in theory should do the job, but do not. Tumor size, for instance: there are drugs that can shrink tumors without prolonging a patient’s life. Bone density is another example. Fluoride can increase it in people whose skeletons have thinned from osteoporosis, so fluoride should prevent fractures. But it doesn’t. In fact, it makes fractures more likely, because it turns bones brittle. ...........

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