Second hand smoke also causes lung cancer.
My friend quit 30 yrs ago and has lung cancer now. If you think direct and second hand smoke doesn't cause lung cancer, you are fooling yourself.
People need to quit while they can. You might be lucky and it won't spread. My husband now has 3 brain cancers too. He didn't quit until now, a year after his lung cancer showed up.
Smoking is the #1 cause of lung cancer and yes the smoker is to blame for his own choices. Make bad choices and get bad things. I smoked too and stopped when my heart did.
I hope those people keep plugging away.