Age has always been an important factor in the occurrence, development and prognosis of various tumor. Squamous cell carcinoma of the head and neck (HNSCC) is generally considered to be more frequent in the elderly, associated with tobacco and alcohol, and mainly occurs in men8. However, more and more young patients with HNSCC have been reported all over the world9. For the past few years, the incidence of OSCC has been on the rise, especially among young patients10.The purpose of this SEER database analysis was to assess the clinical characteristics and risk factors of OSCC in different age groups. At the same time, understanding of other factors (gender, tumor size, histological grade, treatment, etc.) that affect the premature death of patients will help to formulate the corresponding treatment plan in advance and improve the survival rate. To our knowledge, this study is the first to observe the possible differences stratified by age in studies with a large sample size.
As we expected, whether it is OS or CSS, the research shows that the survival time of patients decreases orderly and stepwise with the increase of age group. This result is consistent with other large cohort studies that have been published. A study carried out in Brazil shown that age has a strong impact on mortality from oral and oropharyngeal cancer. The risk increases from 40 years old for men to 55 years old for women and the effect of the overall period was observed11. Laith et al. reported that their study indicated improved OS and disease-specific survival in young patients with oral tongue squamous cell carcinoma (OTSCC)12. But another interesting finding of the regression analysis is that compared with the higher age group, people aged < 30 showed a higher probability of transition, which is not statistically significant 13. Younger age at diagnosis even was found to be a risk factor for the development of pleural metastasis14. In general, the effect of age on the prognosis of OSCC is still controversial. Although a number of studies have made different results, they are unable to explain the etiology and pathological mechanism in detail. From our analysis of the results, young patients (18–39) had a higher rate of surgery (34.11%) and triple therapy (32.05%), indicating that they tend to accept more aggressive treatments.
It has reported that five-year survival rates for patients with oral squamous cell carcinoma vary greatly by stage, from about 90% in the early stage to about 30% in the late stage15. Surgery is the main treatment for early (stage I-II) oral squamous cell carcinoma. Advanced (Stage III-IV) disease indicates difficulty in obtaining a clear incision margin, which means a higher recurrence rate. Under the circumstance, adjuvant therapy is appropriate16. Our research found that age has different effects on prognosis at different stages. In the early stage, the patient's survival period decreased with increasing age. As the stage progresses, the impact of different age groups on the prognosis is less obvious, which is mainly reflected in the poor prognosis of the elderly. Therefore, clinical staging at diagnosis is important and can be used as a predictor of recurrence and death in patients with OSCC.
Based on the results of previous studies, the most common major sites involved in OSCC vary by geographic location. The buccal mucosa is more common in Asian populations, including South Asia, Sri Lanka, etc., where 40% of oral cancers are found in the buccal mucosa due to the common practice of men and women chewing betel nut/tobacco. In contrast, the tongue is the most common site of oral cancer in European and American populations, accounting for 40–50% of oral cancers17,18. The main source of cases in our study is mostly white Americans and our results for the location of OSCC are also within this range. It is worth noting that the proportion of tongue cancer patients is the highest in the 18-39-year-old group (69.29%). This is consistent with a previous study based on a global database analysis19. However, the incidence factors of young people are still unclear, and may be related to changes in the etiology of oral cancer, such as human papilloma virus (HPV) infection. In addition, the Centers for Disease Control and Prevention (CDC) and the Food and Drug Administration (FDA) analyzed data from the 2011–2015 National Youth Tobacco Survey (NYTS) and determined that the use of e-cigarettes and hooks by middle school students has increased significantly, and the trend is much larger than that of adults20. But it is still necessary to further investigate the influence of young people’s eating habits, lifestyle and other factors on their incidence and tumor location.
As a retrospective study we acknowledge there are certain limitations to the study. As for SEER database, a large population retrospective database, inevitably, it has some drawbacks. It does not provide the data of detailed immunohistochemical analysis., for example. It also lacks related chemotherapy or radiotherapy regimens. However, the strengths of our study include a large nationally representative sample, meticulous grouping of age, as well as a wealth of other relevant factors.