Adjuvant Endocrine Therapy in Patients with Ductal Carcinoma In Situ: A Population-Based Retrospective Analysis from 2005 to 2012 in the National Cancer Data Base.

Adjuvant endocrine therapy (AET) has been shown to reduce the risk of second breast cancer events in women with ductal carcinoma in situ (DCIS). There is no population-level evaluation of AET use in DCIS patients after standardized reporting of estrogen receptor (ER) status in cancer registries in 2004. We conducted a retrospective cohort study of women with DCIS in the National Cancer Data Base between 2005 and 2012. Patient, tumor, and treatment characteristics as well as temporal trends associated with receipt of AET were evaluated by generalized linear regression. Among 206,255 DCIS patients, 36.5% received AET. Fewer than half of ER-positive patients (n = 62,146, 46.4%) received AET, with a modest but significant increase over time (43.6% in 2005 to 47.5% in 2012; unadjusted p trend <0.001). AET decreased among ER-negative patients (8.9-6.5%, p trend <0.001) over the same time period. On multivariate analysis, younger (<40 years) and older (≥70 years) women were less likely to receive AET than 50- to 59-year-old women (<40 years: relative risk 0.86, 95% confidence interval 0.82-0.89; ≥70 years: relative risk 0.79, 95% confidence interval 0.77-0.81). ER-positive status conferred a 6.15-fold higher likelihood of receiving AET compared to ER-negative status (95% confidence interval 5.81-6.50). Women who underwent breast-conserving surgery (BCS) with adjuvant radiotherapy were most likely to receive AET. Receipt of AET is relatively low in the group of women most likely to benefit from its use, namely ER-positive patients who underwent BCS. Significant variation exists with respect to patient, tumor, site, and treatment factors. More tolerable drugs or clearer guideline recommendations may increase use.