Is tamoxifen effective in women following surgery for ductal carcinoma in situ (DCIS)?
TYPE OF REVIEW
This is a Cochrane review containing a meta-analysis of two randomized controlled trials.
RELEVANCE FOR NURSING
DCIS is a type of early breast cancer and the fastest-growing breast cancer subtype. It is considered a noninvasive cancer because the tumor doesn't penetrate the epithelial cell basement membrane (the defining characteristic of a cancerous tumor). The global incidence of DCIS has increased significantly in the last 20 years, largely owing to a corresponding increase in screening mammography. The current treatment for DCIS is either lumpectomy with or without radiotherapy or mastectomy to prevent recurrent DCIS and invasive carcinoma. Some patients are also given tamoxifen, a selective estrogen-receptor modulator, but it is unclear whether adding tamoxifen after surgery prevents further episodes of cancer and confers benefit in overall survival. Nurses are often involved in the care of women with breast cancer; therefore it is important to know the effects of postoperative tamoxifen on DCIS.
CHARACTERISTICS OF THE EVIDENCE
The two randomized controlled trials included 3,375 women who had had surgical resection of DCIS. The intervention (regardless of estrogen receptor status) was tamoxifen 20 mg once daily or 10 mg twice daily after surgery with or without adjuvant radiotherapy for five years. Primary outcomes were local recurrence of DCIS, new primary invasive carcinoma (either ipsilateral or contralateral), distant disease (defined as regional or distant nodal disease and metastasis), and all-cause mortality over a minimum of seven years of follow-up.
A meta-analysis based on these two studies revealed that women who received tamoxifen had statistically significant reductions in the recurrence of ipsilateral (same side) DCIS and contralateral (opposite side) DCIS, with a hazard ratio of 0.75 and a relative risk of 0.50, respectively. There was a trend toward a reduction in new primary ipsilateral invasive cancers after treatment with tamoxifen compared with no tamoxifen treatment, however this was of borderline significance (P = 0.06). There was also a statistically significant 43% reduction in relative risk of primary contralateral breast cancers with tamoxifen treatment.
Pooled results of both trials found no difference in risk of overall mortality between tamoxifen treatment and no tamoxifen treatment. The number needed to treat for tamoxifen to have a protective effect against all breast events when taken for five years was 15.
BEST PRACTICE RECOMMENDATIONS
This review found that tamoxifen treatment after surgery for DCIS (with or without adjuvant radiotherapy) reduces the risk of future DCIS, both in the ipsilateral and contralateral breast, compared with no tamoxifen treatment. However, tamoxifen did not reduce the risk of overall mortality in these two trials. A total of 15 women would have to take tamoxifen for five years after surgery for DCIS for one woman to experience a benefit. No significant risk of endometrial cancer from tamoxifen treatment was observed in this meta-analysis; just 10 events (0.5%) of endometrial cancer occurred in 1,798 participants after seven years of follow-up.
More large, multicenter randomized controlled trials are needed to provide data on patient characteristics that may maximize the effectiveness and minimize the risks of tamoxifen.
Staley H, et al. Postoperative tamoxifen for ductal carcinoma in situ Cochrane Database Syst Rev. 2012(10):CD007847