Beta Carotene and Lung cancer

Hi, My father in law has non-small cell lung cancer that has metastisized to his brain and liver.  I started him on the Reliv supplement, but am now concerned because I discovered the NCI studies that indicated beta carotene caused higher incidenes of cancer for smokers.  I am assuming the risk is the same or worse for cancer patients, btw, he is still smoking :-(!!   Do any of you know what amounts are considered unsafe for a smoker/ cancer patient and/or what amounts were used in the study?  Also, are there any supplements without beta carotene?