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Evaluating the Increasing Proportion of Breast Cancer among Patients Aged 21 to 30 Since Year 2016
Conference poster

Evaluating the Increasing Proportion of Breast Cancer among Patients Aged 21 to 30 Since Year 2016

B. Cattelino, J. Yan, T. McKee, S. Yacoub, M. Shriner and R. Kashyap
Clinical cancer research, v 32(4_Supplement), PS5-10-06
17 Feb 2026
DOI: https://doi.org/10.1158/1557-3265.SABCS25-PS5-10-06

Abstract

Background: Recent reports have demonstrated that breast cancer is increasing in women less than age 50. This univariate analysis looks specifically at patients aged 21-30 to evaluate if the proportion of breast cancer is increasing disproportionately in this age group. Method: We utilized data from TriNetX US Collaborative Network, which collates clinical records across 70 healthcare organizations (HCOs). The medical records of over 52 million patients between January 2016 and December 2024 were queried. Records were included in a year-stratified count of breast cancer cases if they contained either the Oncology C50 code for breast cancer or ICD-10 diagnosis code “malignant neoplasm of breast.” We then determined the proportion of total breast cancer cases among 5 age groups (</=20, 21-30, 31-40, 41-50, >50). Chi-square tests were calculated between each year for patients aged 21-30 to assess if the proportion of breast cancer cases in this group has seen an increase year-over-year. Results: Both the absolute number of breast cancer cases in patients aged 21-30 and the proportion of breast cancer in this age group out of total cases increased between 2016 and 2024 (197,313 to 291,750 cases and 0.04% to 0.30%, respectively). There is a significant increase from the baseline year of 2016 in the proportion of cases amongst 21–30-year-olds beginning in 2019 (Diff = 0.0004, X2 = 33.451, p<0.001), and every year after (2020: Diff = 0.0006, X2 = 58.572, p<0.001; 2021: Diff = 0.001, X2 = 127.267, p<0.001; 2022: Diff = 0.0013, X2 = 209.035 , p<0.001; 2023: Diff = 0.002, X2 = 381.962, p<0.001; 2024: Diff = 0.297, p<0.001). (Table 1.) The difference in proportion positives between subsequent years was not significant until 2022-2023.

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