cancer drugs? For example, many of the cancer drugs have their guideline based on the weight of the patient. 

In the US, when FDA approves a drug. One of the very first question is what is the treatment population and at what dose. FDA will not just consider weight, it will also consider age, sex and race as well as many other factors such as certain set of bio-markers.

Don't stay at the understanding that the western medicine treats all the patient using just one dose. It is silly. Different drugs have different toxicities. For some drugs that are relatively safe, the manufacturers provide only a few dose levels so the doctors/patients will have a relatively easy time to follow the treatment directions, hence and better compliance with dose requirements, and hence getting a better outcome. For those drugs with higher toxicities, drug label/treatment guideline is not what you think at all.

Just like Chinese medicine, western medicine does NOT guarantee the outcome. rather than that, it use a process as I said before to establish a BETTER outcome with competitors in each steps. It is precisely this competing process that advance the western medicine.

You are preceding very negative comments as an ill-will attack regardless whether the comments is based on facts or not. This is never the right attitude in real science. I think I said enough.