Updated results of the UK/ANZ DCIS (UK, Australia, and New Zealand ductal carcinoma in situ) trial have reported that both radiotherapy and tamoxifen reduce breast cancer recurrence in women with ductal carcinoma in situ (DCIS). DCIS refers to cancer cells that have formed in milk ducts but are confined there. DCIS is classified as non-invasive because the abnormal cells have not spread beyond the walls of the duct. If left untreated, some DCIS lesions will progress to invasive breast cancer. Initial results of the UK/ANZ DCIS (UK, Australia, and New Zealand ductal carcinoma in situ) trial reported that radiation treatment reduced new ipsilateral (same breast) invasive tumors and DCIS compared with no radiotherapy, but tamoxifen appeared to have no significant effects.
Here, the authors report long-term results of this trial. The study included 1,694 women with completely surgically removed DCIS who were enrolled between May 1990 and August 1998. The recommended dose for radiation was 50 Gy in 25 fractions over a period of five weeks (2 Gy per day on week days), and tamoxifen was prescribed at a dose of 20 mg daily for five years. The primary events studied were new invasive ipsilateral breast tumors for the radiotherapy comparison and any new breast event, including contralateral disease (cancer in the opposite breast) and DCIS, for tamoxifen.
At this point in the trial, all tamoxifen treatments have been completed and the study is in long-term follow-up. After a median follow-up period of 12.7 years, 376 new breast cancers have been diagnosed: 163 invasive (122 ipsilateral, 39 contralateral), 197 DCIS (174 ipsilateral, 17 contralateral), and 16 of unknown invasiveness or laterality. Radiation treatment has been found to reduce the incidence of ipsilateral invasive breast cancer by approximately 70% and ipsilateral DCIS by 60%, but appears to have no effect on contralateral breast cancer (not surprising since the nonaffected breast normally is not treated with radiation). Tamoxifen has also been found to lower the incidence of new breast cancer events, reducing recurrent ipsilateral DCIS by about 30% and contralateral tumors by about 56%, but having no effect on ipsilateral invasive disease. In a separate interview, the authors comment that “this updated analysis confirms the long-term beneficial effect of radiotherapy and reports a benefit for tamoxifen in reducing local and contralateral new breast events for women with DCIS treated by complete local excision.” They conclude: “This trial emphasises the importance of radiotherapy in high-grade DCIS and also suggests a role for tamoxifen primarily for new contralateral disease.”