Second malignant neoplasms in patients with head and neck squamous cell carcinomas.

The incidence of second malignant neoplasms (SMN) was analyzed in 714 patients with squamous cell carcinomas of the oral cavity, oropharynx, hypopharynx and larynx. With a minimum follow-up of 3.5 years and 2,540 person-years at risk 84 SMN (10 synchronous and 74 metachronous) developed in 81 patients. The relative risk of SMN was 2.4. The actuarial method showed an annual incidence of SMN of 3.5%. For oral cavity and oropharyngeal tumors the annual incidence of SMN was 4.0% and 3.8% respectively, compared to 2.1% for laryngeal cancer (p < 0.013 and 0.017 respectively). Sex, age or stage of the index tumor did not significantly influence the annual incidence of SMN. After 3 years of follow-up, SMN became more a cause of concern than loco-regional relapse.