Is daily drinking of large amounts of carrot juice harmful to patients with lung cancer? Mixed info out there, some say it is good, others say v bad

"Diet and cancer" There are some old epidemiologic studies on vitamin A / carotenoids in the diet and risk of squamous lung cancer. Some found the more carrots, the less lung cancer. Others fond the more carrots, the more lung cancer. I'm simplifying, but I'm read to believe these studies are just looking at coufounding variables rather than cause-and-effect and there's no real relationship.