Multiple carcinomas of the large bowel: a natural experiment in etiology and pathogenesis.

One hundred twenty-one patients with two or more large bowel cancers have been studied. An evaluation of the site of incidence of second cancers in patients presenting with metachronous disease supports the concept that increased delivery of bile acids to the colon may play a role in tumor pathogenesis. Because of the extremely high incidence of advanced tumors in patients with metachronous disease, every effort should be made to identify those patients who should undergo a preventive total abdominal colectomy. Newer methods with increased sensitivity are required to improve the follow-up of patients who are prone to develop second neoplasms of the large bowel.