Although RA histotically has come with a lowered life expectancy, it's generally not due to cancer.  I am not familiar with amyloidosis, but found a page with information here. 

According to that page, "Amyloidosis is not cancer, but it is a serious, potentially life-threatening condition that can occur because of some cancers."  I checked out RA in connection to this page and found the following commenting on the different kinds of amyloidosis: "AA amyloidosis. In this condition, the amyloid protein that accumulates in the tissues is known as the A protein. AA amyloidosis is associated with chronic diseases, such as diabetes, tuberculosis, rheumatoid arthritis, or inflammatory bowel disease. It may also accompany aging. The spleen, liver, kidneys, adrenal glands, and lymph nodes may be involved."

I hope this helps.