Breast cancer survival by stage at diagnosis in countries in transition: A population‐based study

This study explores variation in stage-specific survival in women diagnosed with breast cancer in transitioning countries. We obtained data of women diagnosed between 2008 and 2012 from 11 population-based cancer registries (PBCRs) in 10 countries, with follow-up until December 2014. Following stage data standardization and multiple imputation for missing data, we estimated age-standardized 1-, 3-, and 5-year net survival (ASNS) by stage and age group. Stage distribution varied significantly across jurisdictions. Puerto Rico had over 4 in 5 patients diagnosed with early stage (stage I/II), while India, Trivandrum, and Thailand, Khon Kaen had <3 in 5 diagnosed with early stage. Stage-specific ASNS was similar across early stages (stage I/II) but varied markedly for stage IV, where the highest 3-year ASNS (Puerto Rico: 43.2% 95% CI: 38.9%-47.6%) was 20 percentage points higher than the lowest 3-year ASNS (India, Trivandrum: 22.8% 95% CI: 10.2%-35.4%). ASNS for patients 60 years and older was generally lower than for patients younger than 60 years across all jurisdictions. Differences in ASNS were subtle in early stages but were especially pronounced for stage IV, where in Puerto Rico, 3-year ASNS for patients younger than 60 (49.0% 95% CI: 42.7%-55.2%) was over 13 percentage points higher than 3-year ASNS for patients 60 or older (35.4% 95% CI: 29.2%-41.7%). Disparities in breast cancer survival were partly explained by differences in early diagnosis and in care at late stages. Stage at diagnosis is an important indicator that should be collected by registries worldwide, particularly for late-stage disease and older patients.