Postoperative Tamoxifen for ductal carcinoma in situ: Cochrane systematic review and meta-analysis

This review aimed to assess the effects of postoperative Tamoxifen following surgical resection of ductal carcinoma in situ (DCIS). Data on local DCIS recurrence, new invasive carcinoma, distant disease, mortality and adverse effects were extracted from randomised controlled trials (RCTs) comparing Tamoxifen after surgery for DCIS (regardless of oestrogen receptor (ER) status), with or without adjuvant radiotherapy. Meta-analysis was performed using the fixed-effect model and the results expressed as relative risks (RRs) or hazard ratios (HRs) with 95% confidence intervals (CIs). Two RCTs which recruited 3375 women were included. Tamoxifen after surgery for DCIS reduced recurrence of ipsilateral DCIS (HR 0.75; 95% CI 0.61-0.92) and contralateral DCIS (RR 0.50; 95% CI 0.28-0.87). Contralateral invasive cancer was reduced (RR 0.57; 95% CI 0.39-0.83), and there was a trend towards decreased ipsilateral invasive cancer (HR 0.79; 95% CI 0.62-1.01). The number needed to treat in order for Tamoxifen to have a protective effect against all breast events is 15. There was no evidence of a difference in all-cause mortality (RR 1.11; 95% CI 0.89-1.39). Only one trial involving 1799 participants followed-up for 163 months (median) reported on adverse events with no significant difference in event rate between Tamoxifen and placebo groups, but there was a non-significant trend towards more endometrial cancer in the Tamoxifen group. This review concludes that while Tamoxifen after local excision for DCIS, with or without adjuvant radiotherapy, reduced the risk of recurrent DCIS, it did not reduce the risk of all-cause mortality.