"Why all doctors do not follow the same line?"
... because the practice of medicine is more art than science. We are all different and yet same. Our genetics come from two parents and though similar are not identical. And as a result each of us reacts differently to genetic drug treatments.
Also - during clinical trials, they search for the maximum dose before toxicity takes over - "THINKING" that more is better in treating a disease. This is flawed thinking unfortunately (in my opinion due to statisticians dominating the data review process). Biology doesn't work that way. Biology is an interwoven feedback system. Drug interactions and efficacy is different than toxicity and has to be looked at separately. It's hard to do. Only over time - long after a drug is "approved" can data emerge which identify better dosing information.
Your doctor(s) is following old guidelines from "old" data. Show them the paper:
https://onlinelibrary.wiley.com/doi/abs/10.1002/cncr.32504
In the case of dasatinib, less is better if less works. It's a threshold drug where once your body reacts to the drugs action, stop taking more. Increasing drug dose does not increase response - it could even lessen response because toxicity begins to suppress the natural immune system. Finding the correct dose is somewhat unique for each individual, but they are finding individual response can be grouped. For those who suffered with myelosuppression and pleural effusion, lower starting dose is as effective as a higher dose and avoids these adverse events. So rather than start at a high 100 mg dose and induce these adverse events in the first place, they should start at a much lower dose (50 mg) and test response. In chronic phase, there is plenty of time to test. If response is achieved and trends downward (trend down is all that matters). dose could even be lowered further to test continued response. Fine tuning response should be required treatment protocol. I take 20 mg dasatinib. I have no side effects I can feel. And I am "undetected" for over two years. I feel sad for all those patients taking 100 mg and suffering with side effects when a lower dose is likely to be more effective with less side effects.
