The purpose of Neidan is to extend ones life, to become immortal and enlightenment.   I just found this recent interview in which Lawrence Blair states that "John Chang" now has cancer.   I cant help note that Kosta stopped practicing this system because it gave him cancer, also I believe Jim McMillan also got cancer from practicing this form of Neidan.   I know that all members of the Mo Pai are following a secret training manual such as many Taoist Schools utilise. I wonder if the correct technique has not been successfully transmitted through the long history of the School and that mistakes have crept into the practices resulting in this sickness we see in members of this school.