A follow-up study of determinants of second tumor and metastasis among subjects with cancer of the oral cavity, pharynx, and larynx.

We conducted a follow-up study of 380 incident cases of cancer of the oral cavity, pharynx, or larynx, who had been included in a previous case-control study. Information pertaining to potential risk factors, clinical characteristics, and evolution of the tumor (vital status, metastases, and second primary tumors) was obtained. From a multivariate proportional hazard model including terms for risk factors and clinical variables, the incidence of metachronous second primary tumors occurring in the head and neck was positively associated with employment as a farmer as opposed to white collar (hazard ratio [HR] = 3.3) and with tobacco smoking before first tumor diagnosis (HR = 4.3 for heavy versus never or very light smoker). The risk of second primary tumor decreased with increasing dietary "beta-carotene" intake (HR = 0.4 for high versus low intake in tertiles). Less differentiated first primary tumors were followed more frequently by second tumors as compared to grade 1 tumors. The incidence of metastases was not associated with etiological factors of the first tumor, but with stage.