Methods. Using data collected during 1973-1987 by nine population-based cancer registries in the United States, the authors evaluated risks of second primary cancers among 21,371 patients in whom oral and pharyngeal cancers were diagnosed.

Results. The rate of development of second tumors was 3.7% per year. The risk of a second primary cancer was 2.8 times greater than expected, with 20-fold excesses of second oral or esophageal cancers and 4-fold to 7-fold increases of respiratory cancers. Increased risks persisted unabated for cancers diagnosed 5 or more years after oral cancer, suggesting that the second cancers were new primary tumors and not misdiagnosed metastases. The increased risks of second primary tumors were found among both men and women and black and white patients; they were most prominent among patients who were 60 years or younger.

Conclusions. The exceptionally high rate of cancer recurrence among patients with oral cancer (exceeding that for all other cancers) points to the need for close medical surveillance. Special emphasis should be placed on advising patients to avoid or limit consumption of tobacco and alcohol, the main risk factors for oral and most second cancers.