The findings of this study demonstrate the association between the Gini index and all outcomes, showing the significant contribution of social inequality to the diagnosis at late stages of oral and oropharyngeal cancers; moreover, there was an association between lower HDI and higher risk ratio for late diagnosis considering tumor size, which suggests the influence of contextual socioeconomic indicators in the early detection of oral and oropharyngeal cancers. The existence of an association between socioeconomic indicators and oral and oropharyngeal cancers has been well assessed in the literature.[5, 16] It is known that socially disadvantaged groups tend to be more exposed to risk factors for oral cancers, such as tobacco and alcohol use, in addition to worse oral health conditions and underlying nutritional deficiencies.[17] This association, previously known and now corroborated by this study, requires reflection on pro-equity efforts against this disease,[18] and the assessment of existing health policies should also be part of this discussion.
It is noteworthy that coverage by the OHT and the staging of the assessed cancer cases are associated, which indicates that patients in municipalities with greater access to OHT assistance are less likely to receive a diagnosis at advanced stages, when lymph node involvement is considered. Additionally, it has been observed that the risk of receiving a diagnosis at advanced stages of the tumor points to an increase between the years 2000 and 2013 in Brazil. It should be noted that epidemiological studies on the staging of oral and oropharyngeal cancers are scarce in the Brazilian scientific literature. Academic works that analyze the indicators of these diseases associated with the availability of health services in the country are even scarcer.
Regarding oral health care in the Unified Health System, PHC is primarily represented by the OHT of the FHS.[19] Our findings indicate the importance of primary care for oral health and its attributes, such as population health responsibility, formation of bonds, working with priority groups and in a health care network.[20, 21] These characteristics favor preventive actions over risk factors. Additionally, it is understood that the expansion of access to dental care for a historically unassisted population, experienced in Brazil since the implementation of the National Oral Health Policy (PNSB) and put into practice through the OHT, may have impacted on the more timely identification of lesions. The association between OHT coverage and the outcome "lymph nodes", even after adjusting for socioeconomic variables, suggests the offer of this service is a factor that influences the diagnosis at earlier stages of the lesions.
Although little explored, some evidence supports the hypothesis that the restructuring of oral health care in SUS may have a positive impact on oral cancer. This evidence points to access to information about the disease, the demand for dental care and the possibility of identifying tumors at earlier stages, especially in risk groups, all of which are improved by the presence of OHTs. In line with this fact, people living in municipalities with greater PHC coverage are more likely to receive care in advanced health centers.[22, 23] Therefore, it is plausible to establish that the adequate interconnection of health network services (coordinated by PHC), is essential for an effective approach to oral or oropharyngeal cancers.
Our results did not indicate that the greater coverage of Family Health Teams, defined as the priority strategy for PHC expansion and qualification and as the main gateway to SUS,[24] contributes to the early diagnosis of oral and oropharyngeal cancers. Therefore, the importance of the need and expansion of OHT in the country is reinforced. After the publication of the new Primary Care policy in 2017, a movement was observed indicating a reduction in the number of OHTs in Brazil, particularly in the most unequal municipalities in terms of income distribution and larger populations.[25] In this sense, it is worth mentioning the political-economic moment presently experienced by Brazil, of which current government, with the justification of the need for austere measures, has promoted the dismantling and precariousness of SUS, also regarding oral health care, deactivating health units that make up the health network attention (particularly the Dental Specialty Centers). This may imply a weakening of the opportunity for early diagnosis of the neoplasms assessed in this study, which would be a perverse reflection of irresponsible political attitudes, given that the most affected population will be precisely the one who lives in the most disadvantaged places. Extrapolating the attention to oral health, in this context, knowing that these measures affect SUS as a whole, it is worth considering the potential they have to weaken, undermine and, in a very close situation, annihilate the greatest social achievement of the Brazilian population – SUS.
However, it is essential to consider the natural history of oral or oropharyngeal cancers. Both result from the accumulation of genetic mutations throughout life, which means that it takes many years for it to develop, even in cases of massive exposure to risk factors. Emerging evidence data shows that, although alcohol and tobacco consumption is the main risk factor for these diseases, the role played by other factors such as socioeconomic disadvantage, genetics, oral health and human papillomavirus (the latter only for oropharyngeal cancer) has become more evident.[5, 16] Therefore, it is understood that the cases analyzed in this study are due to exposure in previous decades, and, therefore, our findings highlight the role of PHC OHTs in the diagnosis and treatment and not in their prevention role.
Regarding the trend analysis, our study showed that the risk of being diagnosed at more advanced stages was upward for all outcomes. Few possible interpretive dimensions are available to understand this result. The first corroborates a finding that reflects the improved access to the health care network: the tertiary health centers started to treat patients who would previously not have access to the public health system and died after going untreated, consequently, without hospital records. During a similar period, it was observed that the mortality rates from oral and oropharyngeal cancers showed a stable or decreasing trend in almost all regions of the country,[26] which contributes to this interpretation.
The second point of view concerns the quality of health records in recent years: the correct classification of the most severe cases by primary location is a challenge. Therefore, in previous periods, they could have been poorly classified and recorded as due to unclear causes, being better identified and recorded in the analyzed historical series. This might explain the increase in the number of cases with advanced staging found in this study, mainly when we consider that it was only in 2004 that dental surgeons were included in the FHS teams through the implementation of the National Oral Health Policy (PNSB).
The consolidation of the Brazilian primary oral health care has to face many obstacles, mainly regarding the practical application of its principles and guidelines. While the PNSB advocates a new model of care that emphasizes prevention and health promotion in families and communities, individual and curative treatment remains the hegemonic practice in our health system.[18, 21, 27] Coverage, management, structure and vulnerabilities of the work process have been described in the scientific literature.[7, 21, 28] However, we must emphasize that the increased access to dental care observed in the last decades is unprecedented in the history of the country and that, despite some limitations, its pro-equity core seems to prevail.[6] Thus, studies related to the influence of this policy on an outcome as serious as oral and oropharyngeal cancers become, in addition to being necessary, critical for the planning and management of these diseases in the communities.
As limitations of this study, we point out the vulnerability of the database with low completeness of information at the beginning of the series, or the delay in making information available throughout the country at the end of the historical series. Therefore, we chose to perform an ecological study. However, the original internal operational control database validates the data to avoid duplication of records, among others.[8] It is important to note that the analyzed cases do not correspond to all cases of oral and oropharyngeal cancers treated in the hospital environment in Brazil, as the database we use includes only the records sent to SisRHC-INCA. Additionally, the coverage is calculated considering the number of people living in the region and are registered, and not the people using the services. Nevertheless, it is the best and most complete national database available on the evaluated pathologies, since cancer is not a mandatory notification disease in Brazil. The other limitations are intrinsic to its methodological design. They have been widely discussed in the literature,[26] such as the impediments in the processing of aggregated data and the lack of individual data, which are necessary for a more detailed investigation.