Race-related subsequent breast events after ductal carcinoma in situ: A Surveillance, Epidemiology, and End Results–based analysis

Background: The risk of subsequent ductal carcinoma in situ (DCIS) or invasive breast cancer (IBC) has been evaluated in either breast after a DCIS diagnosis; this study modeled competing risks of ipsilateral and contralateral DCIS or IBC subtypes by self-reported race. Methods: A cohort of 198,827 women diagnosed with primary unilateral DCIS between 2000 and 2022 was identified from the US Surveillance, Epidemiology, and End Results tumor registries. Competing subdistributional hazard ratio (sHR) models were used to estimate DCIS or IBC laterality-associated risks overall and for the estrogen receptor (ER+) or progesterone receptor (PR+) overexpressing (ER+/PR+) and ER−PR− expressing tumor subtypes. Cox models were used for subanalysis to estimate the overall risk of a second event (DCIS or IBC). Results: Within an average of 10 (±6.1) years of follow-up after the initial DCIS, 16,148 women had a subsequent event (25.7% DCIS; 74.3% IBC). Overall, compared with White women, Black women had an elevated risk of IBC for either tumor subtype, whereas Asian and Hispanic women had an elevated risk of ER−PR− IBC. For tumor aggressiveness by laterality, Black women had an elevated IBC risk in either breast for ER−PR− (sHR, 1.82; 95% CI, 1.53–2.17 in the ipsilateral breast; sHR, 1.512; 95% CI, 1.24–1.86 in the contralateral breast), as did Hispanic and Asian women in the ipsilateral breast only (with stronger association vs. ER+/PR+) (p_het =.0001). Conclusions: These contemporary data reflect treatment patterns since 2000, which show an elevated risk of subsequent breast tumors in either breast among Black women after DCIS.