Low-dose tamoxifen still prevents recurrence from non-invasive breast cancer

Low-dose tamoxifen for 3 years significantly lowers recurrence from non-invasive breast cancer for 10 years without adverse events. Moreover, the low risk of death strengthens treatment de-escalation in DCIS, results from the TAM-01 trial showed.

Tamoxifen is effective in the adjuvant treatment of HR-positive breast cancer and for the prevention of breast cancer in at-risk women, including those with atypical ductal hyperplasia (ADH), lobular carcinoma in situ (LCIS), and ductal carcinoma in situ (DCIS). However, standard use of tamoxifen (20 mg/day for 5 years) is limited by its toxicity [1]. Previously, results from the phase 3 TAM-01 study (NCT01357772) showed that a low dose of tamoxifen (5 mg/day for 3 years) can halve the recurrence of breast intraepithelial neoplasia with limited toxicity [2]. Dr Andrea De Censi (Ospedali Galliera, Italy) now presented the 10 years of follow-up data from TAM-01 [3].

TAM-01 enrolled 500 patients with hormone-sensitive or unknown breast intraepithelial neoplasia, including ADH, LCIS, and DCIS who were randomised 1:1 to receive tamoxifen (5 mg/day) or placebo for 3 years. The cumulative incidence of neoplastic events after 10 years was 25 in the tamoxifen arm versus 41 in the placebo arm (HR 0.58; P=0.028) demonstrating a carry-over effect of low-dose tamoxifen. With respect to subgroups, a non-significant decrease of ipsilateral breast events (HR 0.68; P=0.227) and a significant decrease of contralateral breast events (HR 0.36; P=0.025) were observed. In the DCIS cohort (n=346), a 50% reduction (HR 0.50; P=0.02) of breast events was observed. The tumour characteristics of the breast neoplastic events were not different between the tamoxifen and placebo arm. Adverse events were not significantly increased in the tamoxifen arm versus the placebo arm.

Based on these results, Dr De Censi concluded that “Low-dose tamoxifen for 3 years significantly lowers recurrence from non-invasive breast cancer at 10 year without adverse events. Moreover, the low risk of death strengthens treatment de-escalation in DCIS.”

1. Noonan S, et al. Cancer Prev Res (Phila). 2018;11(1):38–43.
2. DeCensi A, et al. J Clin Oncol. 2019;37:1629–1637.
3. De Censi A, et al. 10 year results of a phase 3 trial of low-dose tamoxifen in non-invasive breast cancer. Abstract GS4-08, SABCS 2022, 6–10 December, San Antonio, TX, USA.

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Posted on 1 February 2023