Gingival Cancer- Trends in Incidence Among Different Age Groups and Ethnicities- a 35-Year SEER Analysis of US Population

Background: In the United States, nearly 30,000 cases of oral squamous cell carcinoma are diagnosed annually with over 7000 deaths. Gingival squamous cell carcinoma (GSCC) is relatively uncommon, with an incidence less than 10%. It has been reported as the third most common oral cavity site for malignancy after tongue and floor the mouth. The incidence seems to be higher in elderly women without previous history of smoking and/or alcohol abuse. Racial and gender differences in incidence of gingival cancer and the trends over time of gingival malignancies have received less attention in the literature. This study evaluated trends in gingival malignancies with particular emphasis on race and gender in different age groups. 

Material and Method: Data regarding diagnoses of gingival cancer were identified through the Surveillance, Epidemiology and End Results (SEER) program of the National Cancer Institute (NCI). The SEER Program is a public-based registry that estimates the cancer experience for approximately 14% of the US population. The current analysis uses data from SEER 9 Registry. SEER*Stat Statistical software (Rockville, MD) was used to estimate incidence rates age-adjusted to the US 2000 standard population based on the US census. Time periods were examined as 1973-79, 1980-86, 1987-94, 1995-2001, 2002-2008. Age was divided into three cohorts: 0-39, 40-64 and 65+. Race was examined in categories of white, black and other (American Indian/Alaska Native and Asian/Pacific islanders).

Results: There were 15,628 cases of gingival cancer identified between 1973 and 2009 by the SEER database. Between 1973 and 2009, incidence of gingival cancer decreased by 41%. For gingival cancer among the younger age group, black males experienced a higher rate than other groups in the 1970s.

In the older age group, the incidence rate of gingival cancer declined approximately 30% in males across all racial categories, though the rate remained higher in black males followed by white males and males in the other race category. The incidence rate among older females did not appreciably change between 1973 and 2009.

Discussion: In the literature, gingival cancer is an area of interest that has not been explored much. Specifically in our study, the incidence rate among older white women is highest for gingival cancer. This is mainly interesting because of an apparent linkage with a rare and understudied condition, proliferative verrucous leukoplakia (PVL). PVL is a rapidly multiplying wart-like white lesion of the oral mucosa, which is known to especially affect the gingivae of older women who are non-smokers. PVL is characterized by multifocal presentation, which is resistant to treatment and has a high rate of malignant transformation ranging from 60% to 100%. The most frequent location of malignant transformation was found to be gingiva and palate. Because of the verrucal appearance of the lesion, earlier studies suggested a potential role of human papilloma virus (HPV) infection, though more recent studies ruled out HPV as a factor.

Conclusion: For gingival cancer, sex, race and age-specific incidence trends have decreased since the 1970s in the younger population, yet disparities still remain. Incidence rate in the older population has not changed much, especially in white females. These disparities can be attributed to environmental exposures such as alcohol, tobacco, and sexual practices. The fact that disparities do exist, even as incidence decreases, highlights the importance of better documenting major risk factors in population-based registries. These findings reinforce the value of preventative measures in public health, screening tools, and access to care among disparate populations. Documentation of alcohol and tobacco use, as well as HPV status in the future may provide a more inclusive interpretation of the risk factors in certain populations, as well as explain and measure disparities.