Second cancer following cancer of the respiratory system in Connecticut, 1935-1982.

The risk of a person developing a second primary cancer was evaluated in approximately 30,000 persons who developed cancer of the respiratory system in Connecticut between 1935 and 1982. A significant 44% excess of all second cancers was observed following cancer of the lung (614 observed vs. 426 expected). The excess of second tumors was 72% following cancer of the larynx (541 vs. 314) and 34% following cancer of the nasal cavities and sinuses (43 vs. 32). For cancers of the lung and larynx, second cancers arose mainly along the respiratory tract or other sites associated with cigarette smoking (oral cavity, bladder, kidney). A threefold excess of esophageal cancer followed cancer of the larynx, which was indicative of risk factors in common (alcohol and tobacco) and possibly an effect of radiotherapy. Radiotherapy may have contributed also to the increased risk of second lung and breast cancers. A slight excess risk of leukemia after lung cancer points to a possible effect of chemotherapy given for certain histologic types. An unexpected finding was a significant 50% increased risk of colon cancer following cancer of the larynx. Significant excesses of prostate cancer are probably artifacts associated with increased medical surveillance and higher autopsy rates among cancer patients than in the general population. No deficits of any second cancers were observed. The risk of a second cancer developing did not appear to vary by sex or time since initial diagnosis, except that the risks following cancer of the nasal cavities and sinuses returned to normal levels among long-term survivors. Among persons observed for 10 or more years after their initial diagnosis of cancers of the lung or larynx, the risk of developing a second cancer remained high, i.e., on the order of 50% above expectation. Further analytic studies should clarify the role of smoking, alcohol, other life-style and host factors, and various forms of therapy on the risk of second cancers following cancer of the respiratory system.