If Cancer is the chastening tool of God, then doctors who are fighting cancer are fighting against the work of God. If a preacher or a Christian believes the sickness is a means of chastening, then he should never pray for relief from the sickness, but rather pray that the cancer will continue to grow until the chastening is completed.
Each of us should think of the future. Every puff on a cigarette is another tick closer to a time bomb of terrible consequences. Christopher Hitchens didn't care about the consequences of smoking cigarettes. Tragically, he died of throat cancer in December 2011.