Temporal trends in breast cancer case volume, subtypes, and age at diagnosis in Vietnam: An eight-year analysis of 15,227 patients.

Abstract

e23375 Background: Breast cancer subtype distribution and age at diagnosis may differ between Asian and Western populations. We aimed to characterize temporal changes in age at diagnosis and breast cancer subtypes defined by hormone receptor (HR) and HER2 status in a large Vietnamese cohort. Methods: We conducted a retrospective analysis of a breast cancer pathology registry including patients diagnosed between 2015 and 2022 at Vietnam National Cancer Hospital. Collected variables included age at diagnosis, estrogen receptor (ER), progesterone receptor (PR), HER2 status assessed by immunohistochemistry (IHC), and year of diagnosis. HER2 positivity was defined as IHC 3+. Tumors with HER2 IHC 2+ were categorized as HER2-equivocal, as confirmatory in situ hybridization was not routinely available or affordable. Breast cancer subtypes were classified as HR+/HER2–, HER2-positive (IHC 3+), HER2-equivocal (IHC 2+), and triple-negative breast cancer (TNBC). Patients with missing data were excluded. Results: A total of 15,227 breast cancer patients were included. The annual number of diagnosed cases increased from 850 in 2015 to 3,260 in 2022, with a temporary decline in 2021 (1,715 cases), likely related to the COVID-19 pandemic (Table 1). The overall mean age at diagnosis was 57.3 ± 11.8 years and decreased over time, from 62.2 years in 2015 to 53.3 years in 2022. Regarding subtype distribution, 45.8% of tumors were HR+/HER2–, 28.2% were HER2-positive, 13.0% were HER2-equivocal, and 13.0% were TNBC. Overall, 67.9% of tumors were HR-positive. The distribution of HR status and HER2 IHC expression did not differ significantly between patients aged ≤40 years and > 40 years (HR-positive: 70.5% vs 67.7%; HER2 IHC 3+: 28.3% vs 28.2%, respectively; p-values > 0.05). Detailed temporal trends are shown in Table 1. Conclusions: In this large real-world cohort from Vietnam, the number of patients diagnosed with breast cancer increased substantially during the period. Patients were diagnosed at younger ages over time, with a consistently high proportion of HER2-positive disease across age groups. These findings might help to develop context-specific research and health system planning to optimize diagnostic capacity and treatment strategies. Distribution of breast cancer case volume, subtypes, and age at diagnosis over time. Year Total (N) Age, mean ± SD (years) HR+/HER2– (%) HER2-positive (%) HER2-equivocal (%) TNBC (%) 2015 850 62.2 ± 10.7 38.1 25.5 23.4 12.9 2016 1,410 61.1 ± 11.3 42.7 27.6 14.8 15.0 2017 1,640 60.2 ± 11.1 45.1 28.0 13.0 13.9 2018 1,779 59.8 ± 11.0 46.9 28.3 12.9 11.9 2019 2,197 58.3 ± 11.4 49.3 26.9 10.7 13.1 2020 2,376 54.6 ± 11.5 44.1 28.5 14.1 13.3 2021 1,715 56.2 ± 11.5 45.2 29.3 11.4 14.2 2022 3,260 53.3 ± 11.7 48.3 29.1 11.2 11.4 Overall 15,227 57.3 ± 11.8 45.8 28.2 13.0 13.0