No, outside of a laboratory everything influences such signals. First of all, changing medical practice changes how often and in which stages cancer is detected

No, outside of a laboratory everything influences such signals. First of all, changing medical practice changes how often and in which stages cancer is detected and treated. Dealing with that, you have then to deal with changing fashions (less smoking more sushi), and so on. Dealing with all of these is of course error prone and in the end, you can only see very strong effects in real life.