Definition of Oral/Pharyngeal Cancer
Cancers of the oral cavity and pharynx account for 3% of all cancers in the United States. Oral cancer usually includes cancer of the lip, tongue, salivary glands, and other sites in the mouth; while pharyngeal cancer includes cancers of the nasopharynx, oropharynx, and hypopharynx. More than 90% of oral or pharyngeal cancers are squamous cell in origin.
For classification purposes, oral and pharyngeal cancers sometimes are grouped with laryngeal and esophageal cancers, with which they share etiologic features. However, in these background papers, they will not be. Furthermore, oral cancer will be defined to include cancers of the lip, tongue, other mouth sites, and the oropharynx. Cancers of the salivary gland, nasopharynx, and hypopharynx will not be included, as they account for less than 10% of all oral cancers and are etiologically and biologically distinct. Sarcomas will also not be discussed for similar reasons.
Epidemiologic Measures and Data Sources
Incidence, mortality, and survival are the primary measures for assessing the impact of cancer in population groups. Incidence is the frequency of new cancer cases during a defined period of time, generally expressed as the rate per 100,000 persons per year; the mortality rate is the frequency of cancer deaths per 100,000 persons per year. The observed survival rate is the proportion of persons with cancer who survive for a specified period of time after diagnosis, usually 5 years. This statistic is often presented as a relative survival rate, in which survival from cancer is corrected for the likelihood of dying from other causes.
Data for describing the patterns of oral cancer come from two main sources, mortality data derived from death certificates and cancer registries. The National Center for Health Statistics (NCHS), within the Centers for Disease Control and Prevention (CDC), collects and analyzes death certificate data from all 50 states and is the main source of U.S. mortality statistics. These data permit assessment of the incidence, survival, and mortality rates for different segments of the population (defined by age, sex, race/ethnicity, or other characteristics).
Cancer registries attempt to include all cancer cases among residents of a defined geographical area. Data collection involves checking all possible sources of cases—hospitals, pathology laboratories, physicians’ offices, and death records. A number of registries exist in the United States and Puerto Rico. In fiscal year 1994, 37 states received support from CDC for cancer registries: 25 to enhance established registries and 9 to develop registries where none existed. These state-based programs of cancer surveillance, authorized by Congress in 1992, will provide the basis for appropriate policy decisions and allocation of scarce program resources.
The National Cancer Institute (NCI) collects data from nine cancer registries (5 states and 4 metropolitan areas) as part of its Surveillance, Epidemiology, and End Results (SEER) program. Although they are not nationally representative in the statistical sense, the SEER sites were selected for their epidemiologically significant population subgroups and account for about 14% of the U.S. population. For the past 20 years, SEER data have represented the primary
source for statistics on national incidence and survival.
Incidence and Mortality Data
Based on 1991 SEER data, the overall incidence and mortality rates for oral and pharyngeal cancer combined are 10.4 per 100,000 population and 2.9 per 100,000 population, respectively. The annual incidence of 15.7 per 100,000 for males far exceeds the rate of 6.0 per 100,000 for females.(1)
Mortality rates show similar differentials: 4.5 per 100,000 per year for males, 1.7 per 100,000 per year for females. This gender difference is also evident in the lifetime risks of developing oral cancer: 1.5% for males and 0.7% for females (based on 1989-91 incidence rates).
Black males in the United States have an incidence rate of oral cancers about one-third higher than their white counterparts (20.7 versus 15.3 per 100,000 annually) but more than twice the mortality rate (8.9) deaths versus 4.1 deaths per 100,000). In contrast, black women have an incidence rate (6.2 per 100,000) that is similar to that of white women (5.9 per 100,000), although the difference in mortality rates between these groups is more substantial (2.4 versus 1.6 per 100,000).
Geographic variations in mortality have been noted. For the period 1987-1991, states with the highest mortality rates were: Alaska (4.1 per 100,000), Delaware (4.1 per 100,000), South Carolina (4.0 per 100,000), and Louisiana (3.7 per 100,000). The District of Columbia had a mortality rate more than twice the total national rate (6.8 versus 3.0 per 100,000). Arkansas, Idaho, Wyoming, South Dakota, and Utah had the lowest rates (2.2, 2.1, 1.8, 1.7, and 1.3 per 100,000, respectively). From the 1950s through the 1970s, the Southeast had high mortality rates, but these have since decreased.
Trends over time in oral cancer incidence are very different for different subgroups of the population. From 1973 to 1991, the oral cancer incidence rate climbed from 16.8 to 20.7 per 100,000 persons per year among black men, but declined slightly for white men from 17.5 to 15.3 per 100,000. Among women, incidence rates remained relatively constant at about 6.2 per 100,000.
Persons with oral cancer often have multiple primary lesions, and have up to a 20-fold increased risk of having a second oral cancer. Persons with primary tumors of the oral cavity and pharynx also are more likely to develop cancers of the esophagus, larynx, lung, and stomach (2-5)
Differences exist by anatomical site as well. Within the oral cavity and pharynx, 29% of cancers involve the tongue and another 17% the lip. Among pharyngeal sites, the oropharynx is the most common site for tumors (39%), followed by the hypopharynx (32%). (6)
Survival
Five-Year Relative Survival Rates Based on data from 1983-1990, the overall 5-year survival rate for oral cancer was 52.5%. Females fared somewhat better than males (58% versus 50%). Blacks did far worse than whites; only 34% of blacks survived 5 years after the initial diagnosis, compared with 55% of whites. There was a great difference within the black subgroup, however, as the survival rate for black males was only 28%, versus 47% for black females. Overall, the percentage of persons surviving 5 years after the initial diagnosis of oral cancer had not changed appreciably since the 1974-1976 time period.
For cases diagnosed in 1981-1986, the 5-year survival rate for pharyngeal cancers (33%) was slightly more than half that for cancers of the oral cavity (60%). Survival by specific anatomic site ranged from a low of 23% for unspecified or ill-defined sites in the pharynx to a high of 91% for lip cancer. There were significant racial differences for most of the specific anatomic sites, with blacks having poorer survival in each instance. (6)
Five-Year Relative Survival by Historical Stage at Diagnosis
Stage at diagnosis refers to the extent of disease at diagnosis. There are three stages: localized, regional, and distant metastasis. Five-year relative survival rates vary with the stage at diagnosis; localized cancers have the highest survival rates and cancers with distant metastasis the lowest. At diagnosis of oral cancer, most individuals have localized or regional disease: 37%, localized; 43%, regional; 10%, distant; and 10%, unstaged. Five-year survival rates for all oral cancer cases are 79% for those with localized disease, 42% for regional disease, and 19% for disease with distant metastases. (1)
There appear to be no major differences by sex for the distribution of stages at time of diagnosis; however, women with regional and more advanced di