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January 2018

Rethinking Extended Adjuvant Antiestrogen Therapy to Increase Survivorship in Breast Cancer

Author Affiliations
  • 1Department of Breast Medical Oncology, University of Texas MD Anderson Cancer Center, Houston
JAMA Oncol. 2018;4(1):15-16. doi:10.1001/jamaoncol.2017.3510

Extended adjuvant antiestrogen therapy1,2 with either tamoxifen or the aromatase inhibitor (AI)3 letrozole has improved survivorship in patients with breast cancer. Sledge and coauthors state, “it is arguable that antiestrogen treatments have had greater global impact than any other treatment intervention in cancer medicine.”4(p1981) This translational research strategy5 of continuing adjuvant therapy for up to a decade is now considered standard of care. Most importantly, early cessation of adjuvant antiestrogen therapy at 5 years, rather than continuing, increases the risk of recurrence in patients at high risk6 (those with large primary tumors and multiple positive axillary lymph nodes). Clearly, the fact that occult micrometastases have not been killed but remain dormant must now be addressed therapeutically. The advantage of antiestrogen therapy is low cost, but future barriers to combining antiestrogen therapy with precision medicines (palbociclib and everolimus) is the high cost of years of treatment when conventional long-term combination adjuvant therapy is used. Additionally, there will be increases in toxic effects over antiestrogen therapy alone. Both factors conspire to undermine patient adherence, which results in stopping treatment, recurrence, and death.