Date of Award

January 2025

Document Type

Thesis

Degree Name

Master of Public Health (MPH)

Department

School of Public Health

First Advisor

Michaela A. Dinan

Second Advisor

Timothy J. Robinson

Abstract

AbstractBackground: Digital breast tomosynthesis (DBT) has demonstrated improved cancer detection and reduced false-positive and recall rates compared with digital mammography (DM) alone in trials of women aged over 50. However, its benefits for older women remain uncertain. We hypothesized that among women aged 67+, breast cancer detected via DBT are more likely to be invasive lobular carcinoma (ILC) and present at a smaller size at diagnosis, and this association persists among women aged 75+. Additionally, we hypothesized that DBT detects ILC at a smaller tumor size. Methods: We conducted a retrospective cohort study of women aged 67+ with screen-detected ER+/HER2- breast cancer from 2015-2019 using SEER-Medicare data. The exposure was screening modality, dichotomized into DBT versus DM for cancer detection. The primary outcome was tumor histology, dichotomized into invasive lobular carcinoma (ILC) vs. other histology, which included invasive ductal carcinoma (IDC) or mixed ductal lobular histology (MDLC). The secondary outcome was tumor size at diagnosis, categorized as an ordinal variable with bins defined as 0–10 mm, 11–20 mm, 21–30 mm, 31–40 mm, 41–50 mm, and 51 mm or greater. Multivariable logistic regression was used to assess the association between screening modality and tumor histology and ordinal logistic regression was used to examine the association between screening modality and tumor size. Models were adjusted for sociodemographic, health care utilization, and other covariates associated with the exposure and the outcomes in bivariate analyses. To better account for differences in women’s characteristics associated with screening modality at detection, inverse probability weighting (IPW) derived from the propensity score for receiving DBT vs DM was incorporated into all adjusted logistic regressions described above. Results: Among the 12,582 included women, nearly half of them (49.2%) received DBT at breast cancer detection. The majority were non-Hispanic White (82.4%) and not dual eligible for Medicare and Medicaid (89.5%), and over half were aged 67 to 75 (55.8%). Among the overall cohort, 15.1% of the women had ILC and 80.2% had tumors smaller than 20 mm at diagnosis. In multivariable analyses, DBT at breast cancer detection was associated with 24% higher odds of being diagnosed with ILC compared to DM (aOR: 1.25, 95% CI: 1.12–1.39), an association that persisted among women over 75 (aOR: 1.22, CI: 1.10–1.35). DBT was associated with 9% higher odds of being diagnosed with smaller tumors (aOR: 1.09, CI: 1.01–1.17) compared to DM, but this association was not observed in women aged 75+ (aOR: 1.01, CI: 0.91–1.13). No significant interactions were observed between screening modality and tumor histology on tumor size. Conclusions: In this cohort study of women with screen-detected ER+/HER2- breast cancer, DBT at breast cancer detection was associated increased odds of being diagnosed with ILC and a smaller tumor compared to DM. While DBT remained associated with an increased diagnosis of ILC among women aged 75 and older, it was not associated with the diagnosis of smaller tumors in this age group. Our findings support the use of DBT as a routine screening modality to enhance the detection of ILC. However, more evidence is needed to determine whether DBT facilitates earlier cancer detection compared to DM.

Comments

This thesis is restricted to Yale network users only. It will be made publicly available on 06/16/2026

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