Second cancers in patients with chronic lymphocytic leukemia.

Among 419 persons diagnosed as having chronic lymphocytic leukemia (CLL) in western Washington State between 1974 and 1983 and followed through January 1985, 9 subsequently developed other lymphoid cancers and 48 developed nonlymphoid cancers. Only 2 lymphoid and 21 nonlymphoid cancers were expected based on the rates of the western Washington population as a whole. Lung cancer accounted for about one-third of the excess rate observed. Three of the nonlymphoid tumors that occurred in the patients with CLL were classified as malignant fibrous histiocytomas, which represents an exceptionally high relative incidence for this histologic type. The excess risk of nonlymphoid cancers was present in both sexes, across all age categories, and in every length-of-follow-up interval. These results, taken together with those obtained from earlier investigations, suggest that persons with CLL are at increased risk of developing a second tumor, particularly in the lung. The reasons for this increased risk remain to be elucidated.