Mary in Oregon, so sorry to hear about your sister. Folks seem to expect that cancer always has a readily-determined cause, but it just ain't so. This is why it's so important to be screened regularly, even if your family hasn't had a history of cancer in the past. Get that annual mammogram, and the colonoscopy, too, just to catch things early if possible. Wouldn't help much with lung cancer, and I don't know enough to know if there's a screening test for that. Some cancers just don't give us much warning. Hang in there, Mary, and take care.

Pat in Rockport, TX