Tamoxifen/radiotherapy effective in treating locally exposed ductal carcinoma in situ

In women with ductal carcinoma in situ (DCIS) treated with complete local excision, radiotherapy reduces by about 60% to 70% new breast events of ipsilateral invasive and DCIS natures compared with no radiotherapy. In addition, contrary to initial findings, tamoxifen reduces by 30% the incidence of all new breast events as well as recurrent ipsilateral DCIS, and reduces contralateral tumors by about 55%. The conclusions come from an updated analysis presenting the long-term results of the UK/ANZ (United Kingdom, Australia, and New Zealand) DCIS trial.

Researchers recruited women with completely locally excised DCIS into a randomized 2×2 factorial trial of radiotherapy, tamoxifen, or both. The dosage of radiation used was 50 Gy in 25 fractions over 5 weeks (2 Gy per day on weekdays). The dosage of tamoxifen was 20 mg daily for 5 years.

Between May 1990 and August 1998, researchers randomly assigned 1,701 women to receive radiotherapy and tamoxifen, radiotherapy alone, tamoxifen alone, or no adjuvant treatment. In the end, 1,694 women were available for analysis.

Tamoxifen reduced the incidence of all new breast events (HR, 0.71; 95% CI, 0.58–0.88; P=.002), including recurrent ipsilateral DCIS (HR, 0.70; 95% CI, 0.51–0.86; P=.03) and contralateral tumors (HR, 0.44; 95% CI, 0.25–0.77; P=.005). It had no effect, however, on ipsilateral invasive disease (HR, 0.95; 95% CI, 0.66–1.38; P=.8).

While the effect of radiotherapy was similar whether or not women received tamoxifen, the tamoxifen effect appeared only in women who did not receive radiotherapy.

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. 2011;12(1);21-29.