Twenty years of breast cancer epidemiology and treatment patterns in S ã o Paulo, Brazil-observed versus expected treatment utilization in a retrospective cohort

Abstract

Background: Over half of new breast cancer cases occur in low- and middle-income countries, with disparities in survival outcomes due to late-stage diagnoses, healthcare access gaps, and biological differences. This retrospective cohort study examined trends in survival, stage distribution, and treatment utilization for breast cancer in Brazil, an upper middle-income country.

Methods: Patients newly diagnosed with invasive breast cancer between 2000 and 2019 were identified from São Paulo's Oncocenter Foundation registry. Data on demographics, diagnosis stage, diagnosis-to-treatment intervals, and treatments received were analyzed in 5-year blocks. Median overall survival was estimated using the Kaplan-Meier method. Actual treatment utilization was compared to model-based estimates of optimal utilization derived from the National Comprehensive Cancer Network Guidelines' Enhanced and Maximal Resource Modules.

Findings: We included 125,005 patients, with a median age at diagnosis of 55 years (interquartile range 46-75); 99.4% (n = 124,218) were female. The proportion with early disease remained stable over time (61.7% in 2000-2004, 62.4% 2015-2019). Median overall survival increased from 10.7 years (2000-2004) to 11.7 years (2010-2014); median survival for 2015-2019 was not reached. Median overall survival was 20.8, 15.1, 6.8, and 2.0 years for stages I-IV, respectively. Median diagnosis-to-treatment interval more than doubled over time. From 2000 to 2004 to 2015-2019, chemotherapy use decreased from 71.5% to 68.9%; radiotherapy use decreased from 64.0% to 56.5%, and surgery utilization decreased from 80.3% to 74.8%; endocrine therapy use varied between 54% and 62%. Gaps between observed and model-based estimates of treatment utilization were seen across all stages.

Interpretation: Overall survival in patients with breast cancer in São Paulo has improved over time. However, significant treatment gaps and increasing diagnosis-to-treatment intervals suggest systemic barriers to optimal care delivery.

Funding: No funding received.

Keywords: Breast cancer; Chemotherapy; Endocrine treatment; Epidemiology; Guideline concordance; Health policy; Radiation; Surgery.

Fig. 1

Overall survival stratified by cancer stage at diagnosis.

Fig. 2

Changes in breast cancer stage at diagnosis over time.

Fig. 3

Overall survival stratified by year of diagnosis.

Fig. 4

Overall survival according to interval from diagnosis to treatment stratified by stage. DTT interval: diagnosis-to-treatment interval, measured from the date of diagnosis to the date of treatment initiation. Overall survival according to DTT interval was analyzed in patients who received treatment (n = 122,074).

Fig. 5

Comparison of expected and actual treatment proportions for breast cancer across various treatment modalities.

Fig. 6

Survival outcomes based on guideline concordant care for the subset of patients with stage IIIA breast cancer. All = patients received chemotherapy, surgery and radiation in keeping with guideline recommendations. Some = patients received some of the recommended treatments (i.e., at least one of chemotherapy, surgery and radiation), but did not receive all three recommended treatment modalities. None = patients did not receive any of the recommended treatment modalities.