Tumor characteristics associated with tomosynthesis versus digital mammography in older women with screen-detected breast cancer.

BACKGROUND

Digital breast tomosynthesis (DBT) has demonstrated improved cancer detection compared with digital mammography (DM) in trials of women aged 50-74, identifying more invasive cancers and detecting tumors at smaller sizes. However, its benefits for women over the age of 75 have not been examined.

PURPOSE: To assess whether DBT versus DM is associated with favorable tumor characteristics and detection of less conspicuous histologic subtypes in women aged ≥ 75 compared with those aged 67-74, thereby informing screening strategies and overdiagnosis risks.

METHODS

We conducted a SEER-Medicare retrospective cohort study of women aged ≥ 67 diagnosed with screen-detected ER+/HER2- breast cancer from 2015 to 2021. The primary exposure was screening modality (DBT vs. DM). Outcomes included tumor size, nodal involvement, grade, and histology (invasive lobular carcinoma [ILC] vs. other). Multivariable logistic regression was used to assess the association between screening modality and tumor characteristics among women aged 67-74 and ≥ 75.

RESULTS

Among 17,201 women with screen-detected breast cancer, 43.6% were ≥ 75 at diagnosis and 60.4% were detected by DBT. In women aged 67-74, DBT was associated with higher odds of smaller tumors (adjusted odds ratio [aOR] = 1.18, 95% confidence interval [CI] = 1.08-1.29), grade I vs. II or III disease (aOR = 1.14, CI = 1.04-1.26), node-negative disease (aOR = 1.15, CI = 1.00-1.31, P = 0.048), and ILC histology (aOR = 1.29, CI = 1.13-1.48). In contrast, among women aged ≥ 75, DBT remained associated with higher odds of grade I tumors (aOR = 1.21, CI = 1.08-1.35) and node-negative disease (aOR = 1.18, CI = 1.00-1.39, P = 0.049), but was not significantly associated with smaller tumor size (aOR = 0.99, CI = 0.90-1.10) or ILC histology (aOR = 1.13, CI = 0.98-1.32).

CONCLUSIONS

DBT was associated with lower grade and node negative disease in women ≥ 75, but not with smaller tumor size or ILC histology. The incremental advantage of DBT over DM may diminish with age, making the two modalities more comparable in women ≥ 75.