SABCS 2018 — Low-dose tamoxifen reduces recurrence of breast EIN

Why this matters

• Toxicity limits compliance with the standard 20-mg dose.
• 5 mg tamoxifen did not significantly worsen menopausal symptoms or major adverse events vs placebo.

Key results

• Median follow-up, 5.1 years.
• Risk for recurrence was 52% lower with tamoxifen vs placebo (5.5% vs 11.3%; 14 vs 28 events; HR, 0.48; P=.024)
• Tamoxifen was tied to a decreased risk for contralateral breast cancer (CBC; 3 vs 12 cases; HR, 0.24; P=.018). 
• 12 serious adverse events with tamoxifen vs 16 with placebo.
• Rates of venous thromboembolism (VTE) were similar (1 case per group); there was 1 case of endometrial cancer in the tamoxifen group.
  • Expected rates with 20 mg/day tamoxifen would be 2.4 VTE events and 2.7 endometrial cancer cases.
• 4 other neoplasms with tamoxifen, 6 with placebo.
• No significant difference between groups for daily hot flash frequency (P=.05) or intensity (P=.18), vaginal dryness/intercourse pain (P=.57), or musculoskeletal pain/arthralgia (P=.84).

Study design

• Italian multicenter trial of 500 women with IEN randomly assigned to receive 5 mg/day tamoxifen (n=253) or placebo (n=247) for 3 years.
• Funding: Italian Ministry of Health; Italian Association for Cancer Research; Italian League Against Cancer.
• Dr DeCensi reports research funding from Indena SpA, Roche, Pfizer, Janssen, Novartis, Sanofi Aventis, Quintiles, Gilead, and Macrogenics.

Limitations

• Few CBC events.
• 69%-70% DCIS.