As local therapies improve, contralateral breast cancer (CBC) risk for women with ductal carcinoma in situ (DCIS) may exceed the risk of a second ipsilateral breast cancer. We sought to determine whether estrogen-receptor (ER) status influenced CBC risk.
We identified women aged 40-79 with DCIS diagnosed between 1990 and 2002 using the Surveillance, Epidemiology, and End Results database. We used multivariable competing risk regression to examine predictors of time from index DCIS to CBC (invasive or in situ).
Multivariable competing risk regression found ER status to be a highly significant predictor of CBC. The 10-year cumulative incidence was estimated to be 5.3% (95% CI 4.8-5.8%) among ER positive (ER+) cases and 3.3% (95% CI 2.6-4.0%) among ER negative (ER-).
This finding suggests that ER+ DCIS may represent a field effect that confers increased propensity for developing cancer across breast tissue, regardless of laterality. In contrast, ER- DCIS may represent an isolated local event. Given that the majority of DCIS is ER+, and only a minority of DCIS patients receive hormonal therapy, consideration of ER status may influence treatment and surveillance approaches.