This study assessed the trend of mortality from OC and OPC in the last two decades in Brazil and the relationship between these trends and the region's human development, provision of health services, and governmental health expenditures. We found that mortality from both types of cancer decreased in those IGR in which the government spent more on outpatient procedures and hospitalizations and in the more socioeconomically developed ones. The findings suggest that these elements may be effective in reducing mortality from OC and OPC in the country. These findings are the most important result of the study.
In the analysis of association with health service provision, we found evidence pointing to contrasting scenarios. While governmental expenses with outpatient procedures and hospitalizations correlated negatively with mortality trends for both types of cancer, FHS coverage correlated positively. The results we found for health expenditure per capita have already been shown for other types of cancer [19], although they have not yet been explored for OC and OPC. Regions that receive more government transfers for hospitalizations are possibly those that have a greater hospital infrastructure and/or deal more extensively with complex therapies, which are more expensive. Our results suggest that this differentiated structure raised more opportunities for treatment, rehabilitation, and cure of OC and OPC cases, which are treatable cancers – namely, cancers that are associated with survival rates that exceed 50% in five years [20]. The findings related to outpatient expenditures follow the same logic. IGR that have this level of care more productive may have provided more opportunity for early diagnosis, which is a predictive factor for survival in head and neck cancers [21].
The findings regarding FHS coverage do not follow the same reasoning. Coverage by these teams represents access to primary health care, which is the main entryway to the Brazilian Unified Health System (Sistema Único de Saúde). A study carried out in Brazil indicated that coverage by Oral Health Teams – which are part of the FHS – was inversely associated with death rates in men from OC and OPC. The authors justified the results explaining that the FHS promoted the expansion of access to health in unassisted areas [22]. Our results indicated that IGRs with more expressive coverage by FHS have greater APC in mortality. We suggest that they are reflecting the pro-equity character of the implementation of the FHS, which prioritizes more vulnerable regions. Studies that evaluated the impact on the population's oral health have ratified this [23]. Thus, coverage by FHS would be acting as a proxy for the IGR's social development in the analysis. Another possibility is that the IGRs with the broader coverages are those that historically had a more insufficient health provision. In this perspective, the FHS compensates for a historical deficiency not because it prioritizes the most deprived regions but because it is the only health care service available – as it is a more financially feasible solution. Our results suggest that the structuring and expansion of health services in Brazil must occur networked and sync with intersectoral policies for social development to compensate for the inequities in illness and death due to OC and OPC.
We identified that the HDI showed a negative association with the mortality trend, for both types of cancer, considering both sexes and each separately: the more developed the IGR, the greater the decrease in mortality due to OC and OPC. The HDI, which summarizes the dimensions of longevity, education, and income, is lower in the North and Northeast. Explaining this association is complex, as there are several dimensions related to the social determinants of health [24] involved in this relationship. Socioeconomic factors appear to be involved in OC and OPC mortality since exposure to risk factors. A study carried out in Scotland found that, for individuals living in disadvantaged communities, smoking is a mechanism to deal with the stress generated by personal struggles, including economic deficiencies. The obstacles of living in an environment with few opportunities and few resources would intensify these difficulties [25]. Food pattern, inputs and protective or harmful environments [26], occupational exposures [27], and access to health services and health information [5] are all aspects potentially related to OC and OPC and which may be influenced by socioeconomic characteristics. The negative association between mortality and HDI reported here is compatible with previous studies [28–31].
A substantial number of studies on the incidence of OC and OPC in high-income countries have shown trends of increase in the rates of incidence due to OPC in the last two decades, contrasting with a decreasing or stable trends for OC [8, 32–34]. This epidemiological pattern has been associated with the rising role of the Human Papillomavirus (HPV) in the etiology of OPC [35], which is not observed in the OC. In the present study, the similarity in mortality trends for both types of cancer suggests that the predominant risk factors are common and are operating with similar intensity in both anatomical regions, which is not compatible with the course of HPV. This conclusion fits with results of Anantharaman et al. [36]. In a study of 1,420 cases of head and neck cancer, they investigated the percentage of oropharyngeal tumors positive for HPV-16, which was 60% in the USA, 31% in Europe, and only 4% in Brazil. From this perspective, the most classic risk factor (tobacco use) would be operating as a leading etiological factor for OPC incidence and mortality.
We identified higher APCs in mortality rates due to OPC compared to OC in all macro-regions, except for the Southeast. We would expect an opposite situation in a country where HPV is the protagonist of oropharyngeal carcinogenesis. HPV-related head and neck neoplasms are less lethal than non-related ones [37]. A recent multicenter study in Europe found almost 50% of reduction in the risk of death in HPV-16 positive cases of OPC when compared to negative ones [38]. Analyzing a cohort of 235 patients in Scotland, Wakeham et al. observed that patients with high-risk HPV positive OPC had 89% less risk of death than the negative ones [39].
This study used the Brazilian IGR as a unit of analysis. This construct is the product of a new territorial division, which considers the existence of a hub with more complex urban functions for each region. This division respects the concept of network-territory, which reflects the relationship of social subjects with spaces, incorporating their flows and their connections with different territories [11]. Oral cancer and oropharyngeal cancer are severe diseases, which require diagnostic and therapeutic resources of high complexity, usually present in large urban centers. The use of the territorial division in IGR was the strategy that was used to encompass the entire path of the sick individual, without the burden of over-generalization.
This study’s main limitation is its data source, which is an information system – the Mortality Information System. In the last two decades, death records in Brazil have improved substantially [40]. However, its completeness and quality in identifying the underline cause of death vary between regions of the country. An international comparative study of cancer mortality excluded Brazil due to problems with registering the underline cause of death [41]. To counteract this limitation, we corrected the number of deaths of each IGR using the methodology of the Global Burden of Disease Study 2010 [16]. This approach, in addition to considering ill-defined deaths, corrects the “garbage codes”: the deaths registered with codes that do not reproduce the underlying cause of death (for example, “senility”). Besides, concerning primary health care coverage, we only measure FHS coverage, which is the principal strategy for organizing this level of care in Brazil, but not the only one.
The knowledge that factors of socioeconomic origin influence mortality from oral cancer is well established in the literature. The results of this study indicate that the availability of this knowledge was not sufficient to reduce the inequities related to this outcome in Brazil: the less developed regions had the greatest APC of mortality due to OC and OPC. This study innovates in addressing the IGRs as a population aggregate, which tends to encompass the path of patients with cancer in the health care network. It was possible to identify that mortality rates are decreasing in regions that spent more at the outpatient and hospital levels. This suggests that the investment in health care network is effective for this outcome. Finally, when comparing trends in mortality from oral cancer and oropharyngeal cancer, this study found no evidence that, in Brazil, HPV plays the leading etiological factor in oropharyngeal cancer. However, this conclusion requires studies that measure the virus (and other signs of its role as an etiological factor) in these tumors and the incidence of these diseases.