Geographic Variations in Oral Cancer

Geographic Variations in Advanced Stage Oral and Oropharyngeal Cancers in California, 2008-2012

In 2012, 4,061 Californians were diagnosed with cancers of the oral cavity and pharynx, and 973 deaths due to the disease occurred. The oral cavity includes the lip, tongue, floor of the mouth, gingiva, buccal surface (mucosa), hard palate, and oropharynx. Although these sites are accessible for self-inspection or during medical and dental exams, these cancers can often be confused with more common benign lesions. As a result, 60 percent of oral and oropharyngeal cancers are diagnosed after the disease has advanced, when the prognosis for both survival and quality of life are poor. While oral cancer screening is often performed during routine dental exams, in 2012, only 67 percent of Californians reported they had visited a dentist within the past year.¹ Greater awareness and accessibility to dental care is needed to improve the detection of oral and oropharyngeal cancers.

Methods

CASE SELECTION

• The number of oral and oropharyngeal cancers occurring in California was based on new cases of oral and pharynx cancers diagnosed among California residents aged 20 years and older between January 1, 2008 and December 31, 2012 and reported to the California Cancer Registry (CCR) as of June 2015.
• This analysis was based on 18,974 incident or new cases.

GEOGRAPHIC UNITS OF ANALYSIS (E.G. COMMUNITIES)

• The California Office of Statewide Health Planning and Development (OSHPD) has defined 542 Medical Service Study Areas (MSSAs) in California, which are groups of census tracts that make up “rational service areas” for primary health care and are used to identify medically underserved areas.
• All cases were geocoded to a census tract based on the county and street address at time of diagnosis.
• An MSSA code was assigned to each case based upon its census tract.
• OSHPD defines Dental Health Professional Care Shortage Areas (DHPSA) as areas “having a shortage of dental providers on the basis of availability of dentists and dental auxillaries.“²
• Qualifying MSSAs are designated as a DHPSA based on high population to general practice dentist ratio and lack of access to dental care.

DEFINITION OF ADVANCED STAGE

• Using Surveillance Epidemiology and End Results (SEER) summary stage criteria, cases were classified as early stage (in situ and localized) or advanced stage (regional, distant, or unknown stage). For more detailed information on SEER summary stage criteria go to www.seer.cancer.gov.³

COMPARISON GROUP

The comparison group selected was non-Hispanic white persons residing in high socioeconomic status (SES) neighborhoods. (A person’s SES status was ascertained using census indicators of income, employment, and education for the census block group or tract of residence at diagnosis). Non-Hispanic white persons in high SES neighborhoods were chosen as the comparison group because they had the lowest proportion of advanced stage oral and oropharyngeal cancers (60 percent) compared to other race/ethnicity and income groups.

ANALYSIS

• The proportion of oral and oropharyngeal cancers diagnosed at advanced stage in each MSSA was compared to the proportion of oral and oropharyngeal cancers diagnosed at advanced stage in the comparison group. Differences in the sex and age distributions of the two groups were taken into consideration.
• For mapping, communities with a significantly higher proportion of advanced stage oral and oropharyngeal cancer cases were divided into three groups: those where 90 percent or more of all oral and oropharyngeal cancer cases were diagnosed at advanced stage, those where 80-89 percent were diagnosed at advanced stage, and 70-79 percent were diagnosed at advanced stage.
• Percentages of advanced stage oral and oropharyngeal cancers were only mapped in MSSAs that had at least 15 oral cancers cases diagnosed among individuals aged 20 years and older during the study period.

Conclusion

Geocoded registry data have been mapped to show communities with an excess of oral and oropharyngeal cancer cases diagnosed at advanced stage. These maps are now available on the CCR website. Each map shows the MSSAs within the county and the percentage of advanced stage oral and oropharyngeal cancers in the MSSAs. Accompanying each map is a table that details the study results and the demographic information for each MSSA. Below is a summary table displaying the MSSAs with statistically higher proportions of advanced stage oral and oropharyngeal cancers.

References

• California Behavioral Risk Factor Surveillance Survey, 2012. California Department of Public Health.
• Office of Statewide Health Planning and Development. Healthcare Workforce Development Division: Dental Health Professional Shortage Area (http://www.oshpd.ca.gov/HWDD/DHPSA.html).
• Surveillance, Epidemiology, and End Results Program. National Cancer Institute.