Age, surgery, and radiation were associated with the initiation of tamoxifen after ductal carcinoma in situ (DCIS), whereas increasing estrogen receptor (ER) testing since 2001 did not correlate with endocrine therapy initiation, a study published online ahead of print in the journal The Oncologist has shown.1

Although national guidelines recommend considering tamoxifen for women with ER-positive DCIS or who undergo excision alone, endocrine therapy initiation after DCIS is highly variable and largely unexplained. Therefore, researchers sought to evaluate endocrine therapy use after DCIS over a 15-year period in an integrated health care setting to identify factors that impact initiation.

For the study, researchers analyzed data from 727 women age 18 to 89 years with DCIS from the Female Group Health Cooperative. Of those, 22% had initiated endocrine therapy.

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Results showed that younger women (age 45 to 54 years) were more likely to initiate endocrine therapy compared with older women (age 65 to 74 years; RR, 1.69; 95% CI: 1.16-2.46).

Researchers found that women who underwent breast-conserving surgery alone (RR, 0.46; 95% CI: 0.25-0.84) or mastectomy (RR, 0.54; 95% CI: 0.39-0.75) were less likely to receive endocrine therapy than women who underwent breast-conserving surgery plus radiation.

“Contrary to the suggested guidelines, women who had breast-conserving surgery without radiation were less likely to use tamoxifen than those who had radiation,” the authors said.

In contrast, the study demonstrated that ER testing, which increased from 4% of DCIS cases in 2001 to 71% of cases in 2011, was not associated with endocrine therapy initiation. More specifically, endocrine therapy initiation decreased from 58% of ER+ DCIS cases in 2001-2005 to 27% of cases in 2009-2011.

“In this study, the rapid increase in ER testing caused by tamoxifen’s approval in 2000 did not lead to increases in endocrine therapy initiation, despite recognition of an increasing number of DCIS tumors as ER+ each year,” the authors note.

Future approvals by the US Food and Drug Administration of new endocrine agents for patients with DCIS may provide an opportunity to underscore benefits to patients by ER and surgery status.


1. Nichols HB, Bowles EJ, Islam J, et al. Tamoxifen initiation after ductal carcinoma in situ [published online ahead of print January 14, 2016]. Oncologist. doi:10.163/theoncologist.2015-0310.