My Younger Sister Has A Hard Time Swallowing Lettuce And

My younger sister has a hard time swallowing lettuce and a few other foods, our oldest sister just passed away from lung cancer, she was a smoker, she had a very hard time keeping food down, this went on for 2 years before they found the cancer, this sister does not smoke and drinks very little, we have a large amount of cancer in our family, 3 different yes, breast, lung, bone, we are very watchful when something is out of sink with out body's, what can we check to see what is wrong