Second cancer following cancers of the buccal cavity and pharynx in Denmark, 1943-80.

Cancers of the buccal cavity and the pharynx are not only anatomically related but, except for the nasopharynx, also have risk factors in common. Multifocal occurrence of cancers in the buccal cavity and pharynx must be kept in mind when one is interpreting findings on multiple tumors. However, susceptibility to common risk factors, predominantly alcohol and tobacco, seem to be in operation among males, inasmuch as excess lung cancer followed cancers of the tongue [relative risk (RR) = 2.2], other parts of the mouth (RR = 2.2), and pharynx (RR = 2.0). Among females, lung cancer was in excess after cancers of the tongue (RR = 3.7) and mouth (RR = 3.6). Among males, esophageal cancer was elevated after cancers of the mouth (RR = 4.7) and tongue (RR = 5.7). Other combinations of tobacco-related cancers among males include those of the bladder (RR = 2.5) after cancer of the tongue and larynx (RR = 5.4) after pharyngeal cancer. Common etiologic factors or the multifocal nature of tumors of the buccal cavity might also account for the increases of cancer of the mouth (RR = 2.6) following lip cancer and cancer of the tongue (RR = 14) following mouth cancers among males. Among females, cancer of the mouth (RR = 17) was elevated after tongue, tongue (RR = 31) after mouth, and tongue (RR = 10) after salivary gland tumors. The excess of pharyngeal cancers in women (RR = 19) following cancer of the lip may be explained by common risk factors. Observed deficits of colon cancer following cancer of the lip in males and after tongue and salivary gland tumors in females could reflect low socioeconomic status, although a deficit of stomach cancer among males (RR = 0.1) also followed cancer of the salivary glands.