Opportunities and challenges of long term anti-estrogenic adjuvant therapy: treatment forever or intermittently?

ABSTRACT

Introduction: Extended adjuvant (5–10 years) therapy targeted to the estrogen receptor (ER) has

significantly decreased mortality from breast cancer (BC).

Areas covered: Translational research advanced clinical testing of extended adjuvant therapy with tamoxifen or aromatase inhibitors (AIs). Short term therapy or non-compliance increase

recurrence, but surprisingly recurrence and death does not increase dramatically after 5 years of adjuvant therapy stops.

Expert commentary: Compliance ensures optimal benefit from extended antihormone adjuvant therapy.Retarding acquired resistance using CDK4/6 or mTOR inhibitors is discussed. Preventing acquired resistance from mutations of ER could be achieved with Selective ER Downregulators (SERDs), eg fulvestrant. Fulvestrant is a depot injectable so oral SERDs are sought for extended use. In reality, a ‘super SERD’ which destroys ER but improves women’s health like a Selective ER Modulator (SERM), would aid compliance to prevent recurrence and death. Estrogen-induced apoptosis occurs in 30% of BC with antihormone resistance. The ‘one in three’ rule that dictates that one in three unselected patients respond to either hormonal or antihormonal therapy in BC occurs with estrogen or antiestrogen therapy and must be improved. The goal is to maintain patients for their natural lives by blocking cancer cell survival through precision medicine using short cycles of estrogen apoptotic salvage therapy, and further extended antihormone maintenance.

KEYWORDS:

• Adjuvant therapy
• Breast Cancer
• antiestrogen
• estrogen-induced apoptosis
• tamoxifen
• aromatase inhibitors

Declaration of interest

V Craig Jordan declares honoraria from Sermonix (with whom he is also a board member) and Shenogen. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Additional information

Funding

This work was supported by the National Institutes of Health NIH, MD Anderson’s Cancer Center support grant CA016672 and Susan G. Komen under award number SAC100009, and Cancer Prevention Research Institute of Texas (CPRIT) for the STARs and STARs Plus Awards.