what s behind the big drop. you ve got to do your homework first. reporter: mother of two amanda has never smoked so when she was diagnosed with stage four lung cancer, she was shocked. i asked theleft weeks to nine months reporter: now more than three years to live. later, there s no sign of the disease a new report from the american cancer society found the largest year-to-year drop in cancer mortality ever recorded lung cancer and melanoma patients especially benefitting from new drugs that use their own immune system to fight the disease. we re discovering that medicines can really make a difference it s not just earlier diagnosis and prevention strategies. reporter: cancer is still the second leading cause of death for americans and according to the report, progress is stalling on some forms of the disease. colo-rectal cancer and breast cancer are of concern because we have very good screening for the cancers and not everybody is taking advantage of that. reporter: