Multiple primary squamous cell carcinomas in the upper digestive tract.

Multiple squamous cell carcinomas are common and patients carry a constant and excessive risk of developing a new cancer at any time (13-21 X the normal). Among 6,203 cases of primary squamous carcinoma of the upper digestive tract, 648 patients (10.4%) developed two or more independent tumors. Altogether, 761 additional malignancies were observed, with up to five cancers being seen in individual patients. There were 279 patients with a prior or synchronous cancer and 409 patients who developed 462 metachronous tumors. There was a substantial risk for developing a second primary cancer in the upper aerodigestive tract. Overall the observed to expected ratio was 2.48, specifically 2.32 for males and 2.89 for females.