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Home > Understanding Breast Cancer > Breast Cancer Research > Table 45: Tamoxifen in the treatment of ductal carcinoma in situ (DCIS)


Table 45: Tamoxifen in the treatment of ductal carcinoma in situ (DCIS)


This summary table contains detailed information about research studies. Summary tables offer an informative look at the science behind many breast cancer guidelines and recommendations. However, they should be viewed with some caution. In order to read and interpret research tables successfully, it is important to understand some key concepts. Learn how to read a research table

Introduction: Ductal carcinoma in situ (DCIS) is a non-invasive breast cancer. In situ means "in place." In DCIS, abnormal cells are contained in the milk ducts, but have not invaded nearby breast tissue. Without treatment, DCIS can progress to invasive breast cancer over time, so all cases of DCIS are treated (learn more).

Results from one randomized controlled trial showed tamoxifen can lower the risk of invasive and non-invasive breast cancer, both in the breast treated for DCIS and in the opposite breast, in women with DCIS who have lumpectomy plus radiation [1]. The benefit of tamoxifen appeared to be limited to women with estrogen receptor-positive DCIS [2].

A second randomized controlled trial found tamoxifen did not lower the risk of invasive cancer in the same breast, but did lower the risk of invasive cancer in the opposite breast. In contrast, findings from this trial showed tamoxifen lowered the risk of DCIS recurrence in the same breast, but did not lower the risk of DCIS in the opposite breast [3].

Learn more about treatment for DCIS.  

Study selection criteria: Large randomized controlled trials and meta-analyses.

Table note: Relative risk above 1 indicates increased risk. Relative risk below 1 indicates decreased risk.


Study Population
(number of participants)


Absolute Risk of Invasive Breast Cancer per year
(number of cases per 1,000 women)

Relative Risk of Invasive Breast Cancer in Women Taking Tamoxifen Compared to Women Not Taking Tamoxifen,
RR (95% CI)

Among Women Not Taking Tamoxifen 

Among Women Taking Tamoxifen 

Randomized controlled trials 

National Surgical Adjuvant Breast and Bowel Project, Protocol B-24 [1-2]

1,799 women with DCIS treated with lumpectomy plus radiation


19 per

6 per


UK Coordinating Committee on Cancer Research [3]

1,576 women with DCIS treated with lumpectomy either with or without radiation






Staley et al. [4]

2 studies

      Breast treated for DCIS:

Opposite breast:

* Relative risk for invasive breast cancer in the breast treated for DCIS. Relative risk for invasive breast cancer in the opposite breast was similar, 0.68 (0.48-0.95). When results for 732 of participants were examined by hormone receptor status, relative risks showed benefit for hormone receptor-positive DCIS, but no benefit for hormone receptor-negative DCIS.

† Absolute risk not given. However, there was no statistically significant difference between rates of invasive breast cancer for women not taking tamoxifen and women taking tamoxifen (9.1% vs. 8.5%).

‡ Total invasive breast cancer (most breast cancers occurred in the breast treated for DCIS)



  1. Wapnir IL, Dignam JJ, Fisher B, et al. Long-term outcomes of invasive ipsilateral breast tumor recurrences after lumpectomy in NSABP B-17 and B-24 randomized clinical trials for DCIS. J Natl Cancer Inst. 103(6):478-88, 2011.
  2. Allred DC, Anderson SJ, Paik S, et al. Adjuvant tamoxifen reduces subsequent breast cancer in women with estrogen receptor-positive ductal carcinoma in situ: a study based on NSABP protocol B-24. J Clin Oncol. 30(12):1268-73, 2012.
  3. Cuzick J, Sestak I, Pinder SE, et al. Effect of tamoxifen and radiotherapy in women with locally excised ductal carcinoma in situ: long-term results from the UK/ANZ DCIS trial. Lancet Oncol. 12(1):21-9, 2011.
  4. Staley H, McCallum I, Bruce J. Postoperative tamoxifen for ductal carcinoma in situ. Cochrane Database Syst Rev. 10:CD007847, 2012.

Updated 01/13/14