[Statistical survey of multiple primary cancers of the head and neck].

The incidence and factors associated with multiple primary cancer were surveyed and analyzed from April 1978 through December 1990 in our clinic. Fifty-nine cases with multiple primary cancers were selected for study from among 579 cases with malignant head and neck region tumors. The cancers involved the larynx in 17 cases (8.4%), oral cavity in 14 (19.4%), oropharynx in 13 (41.9%), hypopharynx in 7 (8.0%) and nasal cavity or paranasal sinus in 7 (8.0%). Twenty-one cases (35.6%) arose synchronously within one year. From our observations, heavy drinking and smoking were most strongly suspected to be risk factors for induction of malignancy. Most multiple primary cancers in the head and neck region were observed to coexistent in a "so called multicentric zone" consisting of the oral area, pharyngeal area, larynx, esophagus, stomach, and tracheobronchial tree. To avoid overlooking concealed cancer in the multicentric zone, upper gastro-intestinal endoscopy, bronchial endoscopy, chest X-ray and sputum examination should be performed for screening of patients with head and neck malignancies.