The incidence and characteristics of oral cancer shows geographical variations, which occur due to socioeconomic conditions, smoking, alcohol consumption, and lifestyle habits. In this study, we described the characteristics of Beijing inhabitants with OSCC in our hospital.
This study showed the high proportion of female patients with OSCC. Previous reports in China showed that the male: female ratio ranged from 1.94–3.19:1 in different districts 7, 8, 9. The male: female ratio has reduced from 6:1 in 1950 to approximately 2:1 at present10. Whereas, The male: female ratio was 1.1:1 in this study, which was very close to that reported by a retrospective study in Norway11. Fu et al. reported that the male: female ratio for oral cancer incidence across 10 years (2003–2012) in Shanghai City was 1.41:13. In recent years there has been a trend of increasing proportion of women with OSCC; this may be due to their growing consumption of tobacco and alcohol2. However, of the female patients in this study, only 5.5% smoked and 0.7% drank, indicating the influence of other risk factors. Suba et al. reported that female oral cancer patients were significantly older at diagnosis than their male counterparts, and the ratio of non-smokers, non-drinkers among elderly female oral cancer cases was surprisingly high, which was in accordance with this study12. Suba et al. put forward the estrogen deficiency hypothesis in 2007, stating that estrogen deficiency and elevated fasting glucose in postmenopausal women may increase their risk of oral cancer12,13. According to a Beijing health report in 2013, the average life expectancies of men and women were 79 and 83 years, respectively. A longer life-expectancy for women suggests more years after menopause, a longer exposure to the risk of estrogen deficiency, and consequently a higher risk of OSCC. The estrogen deficiency hypothesis could explain the higher age peak of women with OSCC and the high ratio of non-smokers and non-drinkers among female OSCC.
OSCC mainly occurs in older people. The average age at the time of diagnosis is approximately 60 years10. Previous domestic studies indicated that the mean age of diagnosis was 54–60 years8,9. In this study, the median ages of male and female patients were 63 and 66 years, respectively. The median age at the initial diagnosis of oral cancer in Shanghai was 64 years (males: 62 years; females: 69 years)3. At the time of diagnosis in this study, 2.3% patients were younger than 40 years, which was lower than what has been reported globally(5%)10.
The cancer sites in this study in decreasing frequency of occurrence are as follows: tongue, gingiva, buccal mucosa, oral floor, oropharynx, lip and palate. This is similar to that of previous domestic reports7, 8, 9. A previous study utilizing the Surveillance, Epidemiology, and End Results (SEER) database included 20,647 patients with OSCC diagnosed between 1975 and 2013. In that study, floor of the mouth and oral tongue represented the most common disease subsites, followed in descending order by gums, retromolar trigone, buccal mucosa, and hard palate14. In regions of China, South East Asia, and India, however, carcinoma of the buccal mucosa is one of the most common forms of OSCC15,16,17. The difference in the predominant sites of occurrence of cancers may largely be related to various habits prevalent in the respective regions, such as the incidence of OSCC of the buccal mucosa results from the endemic regional practice of chewing betel quid.
Oral cancer can be macroscopically observed and touched, unlike cancers at many other sites, and diagnostic methods are available for early detection. Despite this, most patients were advanced stage at diagnosis. Tsai et al. reported that of the 16,691 oral cancer patients, 67.2% were found to be in stage III or IV diseases when they searched for treatment18. In this study, more than half of the patients in the present study (52.4%) were at stage III and IV. Late stage diagnosis is often associated with low social-economic status.
OSCC is considered a cancer with a poor prognosis, since the 5 year survival rate is reported as 50–63%19, 20, 21. In the Southern region of Thailand, the 5 year survival rate was 24.1%, which was attributed to the advanced stage of the disease when the patients were diagnosed and to the type of treatment provided22 . A study carried out in the Netherlands, from 1989 to 2011, demonstrated that patients diagnosed with oral and oropharyngeal SCC responded better to treatments, increasing the survival rate to 67% and 48%, respectively, in cases of oral cavity and oropharyngeal cancers23. Quinlan-Davidson et al. studied 289 patients with OSCC who were treated with surgery followed by postoperative intensity modulated radiotherapy and observed a 5-year overall survival of 57%24. Some authors reported that survival rates were better in more developed countries than in developing ones25. The 5-year survival (64.0%) in this study was similar to that of SEER(65.3%)26. The differences in the overall survival may be attributed to variabilities in stage distribution; site distribution; and other variables such as host characteristics, comorbidity, and treatment policy27.
The prognosis of OSCC worsened with the progressing TNM stage28. In a nationwide cohort study of 16,691 oral cancer patients who underwent treatment between 2004 and 2008 in Taiwan, Tsai et al. found that the survival rate of oral cancer patients was 82.3% for stage I, 72.6% for stage II, 62.3% for stage III, and 39.2% for stage IV18. Multivariate analysis in the present study showed T3–4 and lymph node metastasis were independent prognostic factors. Lymph node metastasis had more prognostic significance than tumor size.
The association between tumor differentiation and prognosis is controversial. Most studies regarded differentiation as prognostic factor29, 30. Some authors considered that differentiation exerted no influence on prognosis31. Univariate analysis of OSCC with surgery showed that moderate and poor differentiation were independent prognostic factors. Multivariate analysis indicated that differentiation was not an independent prognostic factor. The prognostic significance of tumor differentiation was weaker than that of TNM stage.
This study has several limitations that should be addressed. First, this study on oral cancer was conducted in a single hospital, with a sample size of 604 patients in 10 years, which is relatively small. Second, since human papillomavirus (HPV) testing for oropharyngeal cancer has not been conducted in our hospital for nearly two years, there is a lack of HPV data in previous patients. Our next move is to extend the study to all hospitals in Beijing, which will help us acquire a full knowledge of the characteristics of Beijing OSCC.