In this population-based study that accessed data from 2,715 women with breast cancer in a large city in Brazil, it was observed that the average age of women at diagnosis was 58.6 years, that the diagnoses were early and that the five years overall survival (5yOS) was 80.5%. Survival was significantly lower in more advanced stages and older women. It is the largest Brazilian cohort of survival assessment of the last ten years, just after the period when mammography has significantly spread in Brazil.
The universal health care system in Brazil has expanded significantly over the past decade, increasing the provision of services and cancer care qualification. Particularly in São Paulo State, mammography has been established to screen and early detection of breast cancer [14]. A significant increase in mammography access was observed in the region through national cancer control program incentives [15]. The expansion of the chemotherapy offer and the inclusion of new drugs allowed the transition to less radical treatment modalities, with less morbidity, besides being more effective.
Two results were expected in the implementation of these actions: downstaging and improvements in survival. In this study, we observed that one in every four women with breast cancer in Campinas was diagnosed in clinical stage I. A hospital-based cancer registry study of São Paulo state observed a significant upward trend in the proportion of cases diagnosed in stage I and a significant reduction in stage II cases from 2000 to 2015 [16]. This detection of tumours in earlier stages is firmly attributed to expanding the screening and early detection incentives.
In this study, the 5yOS in stages I and II were 92.6% and 89.4%, respectively (p = 0.058), which means that the survival of radiologically or clinically detected cancers were. It is an argument to do not support screening. However, it is possible that the morbidity related to the earlier treatment would result in a better quality of life for the survivors. Another interesting result is that women diagnosed in stage 0 (in situ) corresponded to 15.4% of cases, the upper limit recommended for a screening program [17], indicating overuse and possible overdiagnosis.
The observed 5yOS was 80.5%, and the ten years overall survival (10yOS) 69.9%. A population-based study in Barretos, 350km far from Campinas, reported a slightly lower 5yOS of 74.3% from 2000 to 2015 (n = 2,110 cases) [10]. Considering both cities' health care framework are relatively similar, these results are likely to indicate improved treatment assistance in the region. The large global survival surveillance consortium, the CONCORD study, updated its third version pointing to a 5yOS for Brazil of 73.9–76.5% from 2000 to 2014, a period less sensitive to reflect the recent improvements observed in recent years [2].
This 5yOS of 80.5% is lower than that found in high-income countries but higher than low and middle-income countries. It is challenging to consider the differences in the periods of observation [2, 18]. From the public health perspective, this result indicates that Brazil's path in terms of investments resulted in a positive impact. Still, the sustainability of these actions is necessary to maintain the achievements. Age, stage and treatment are the factors that most influence the woman's prognosis. It should be noted that, even though there is a tendency for downstaging in Brazil, the proportion of cases diagnosed in advanced stages is still high [16].
In the multivariate analysis, compared to women in stage I, the risk of death was 34% lower for women in stage 0 (in situ), and 1.5, 4.1, 8.6 and 2.1 times higher, respectively for women in stages II, III, IV and unknown. The 5yOS for stages 0, I, II, III and IV was respectively 95.2%, 92.6%, 89.4%, 71.1% and 47.1. These survivals are close to those observed in other national studies [10, 19, 20] and lower than those found in countries like U.S.A. and England [5, 9].
The highest mean and 5yOS were found in the group of women aged 40 to 49 years (9.1 years; 95% CI 8.9–9.3, 87.7%), reducing significantly after 50 years. The multivariate analysis obtained a risk of death 2.3 and 4.2 times higher, respectively, for women between 70 to 79 years old and older than 79 years old; and 26% lower for those between 40 to 49 years old, compared to women between 50 to 59 years old. These results support the evidence that older women have a worse prognosis regardless of the stage at which they are diagnosed [5, 19]. However, very young women (those under 40 years old) had a 5yOS of 82.2%, significantly less than women aged 40 to 49, 87.7% (p = 0.002). Other studies also point to reduced survival in very young women [7, 8, 20], probably due to the diagnosis of more aggressive molecular types of tumours found in this group.
This study is the largest population-based cohort published in Brazil in recent years and has benefited from the multiple data sources for its progress. Its results reflect the reality of Brazil's most populated cities, with different access and quality of care, and can guide public policies for cancer control. The current study's solidness dwells on the number of patients and the reliability of the follow-up. The active search of vital status allowed us to reach higher quality to the data presented.
There are two main limitations. The first is that in 25% of cases the stage was unknown. Secondary analyzes of these cases were carried out, and it was observed that the mean age and mean survival were slightly higher among those not staged (p < 0.001 and P = 0.027, respectively). It may indicate that if it had any influence on the results, it would be discreet.
The second limitation is that in 85% of the cases considered alive, it was impossible to establish the date of censorship. It may have significantly influenced the results of 10yOS and, less significantly, 5yOS an mOS. However, this is a problem inherent in population-based studies. It must be said that death records in São Paulo state are of high quality and that the analysis of the registers of women's economic activities may have mitigated this bias. We consider that given the lack of population-based studies in low and middle-income countries, the data presented is relevant even with its limitation. Its quality should be carefully evaluated compared with data from countries with well-established registration systems.