Research table: Tamoxifen for treatment of DCIS

This summary table contains detailed information about research studies. Summary tables are a useful way to look at the science behind many breast cancer guidelines and recommendations. However, to get the most out of the tables, it’s 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. 

Without treatment, DCIS can progress to invasive breast cancer over time. So, almost all cases of DCIS are treated.

In women with estrogen receptor-positive DCIS who have a lumpectomy plus radiation therapy, tamoxifen may lower the risk of:

• DCIS recurrence (a return of DCIS)
• Invasive breast cancer

These risks are lowered in both the treated breast and the opposite breast.

Learn more about treatment for DCIS.

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

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

Study	Study Population (number of participants)	Follow-up (years)	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 clinical trials
National Surgical Adjuvant Breast and Bowel Project, Protocol B-24 [1-2]	1,799 women with DCIS treated with a lumpectomy plus radiation therapy	17	19 per 1,000	6 per 1,000	Breast treated for DCIS: 0.68 (0.49-0.95)* Opposite breast: 0.68 (0.48-0.95)
UK Coordinating Committee on Cancer Research [3]	1,576 women with DCIS treated with a lumpectomy either with or without radiation therapy	13	†	†	0.81 (0.59-1.12)‡
Meta-analyses
Staley et al. [4]	2 studies				Breast treated for DCIS: 0.79 (0.62-1.01) Opposite breast: 0.57 (0.39-0.83)

* When results for 732 participants were examined by hormone receptor status, relative risks showed benefit only for those with hormone receptor-positive DCIS (no benefit for hormone receptor-negative DCIS).

† Absolute risk was not given. However, there was no difference between rates of invasive breast cancer for women not taking tamoxifen and women taking tamoxifen (9% vs. 9%).

‡ Results for all invasive breast cancers (most breast cancers occurred in the breast treated for DCIS).

References

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 09/11/23