Posted online June 28, 2010, on www.jco.org [1].

A new study of nearly 8,800 early stage breast cancer patients has found that fewer than half -approximately 49 percent - completed the full 4.5 year course of hormone therapy treatment, even though hormone therapy with tamoxifen and/or aromatase inhibitors has been proven to dramatically reduce risk of cancer recurrence and death for patients with hormone-sensitive breast cancers.

The researchers in this study, published in the Journal of Clinical Oncology, said several factors were associated with stopping hormone therapy or taking it inconsistently, including age (younger than 40 and older than 75), lumpectomy as opposed to mastectomy, and having multiple other illnesses. Factors such as Asian/Pacific Islander ethnicity, prior chemotherapy, being married and longer prescription refill intervals were associated with completing the recommended 4.5 years of hormonal therapy as prescribed.

Other small studies have indicated that only approximately 40 to 60 percent of breast cancer patients finish their recommended course of therapy. To take a closer look at this issue, researchers in this study examined automated pharmacy records of 8,769 women diagnosed with either stage I, stage II or stage III, hormone-sensitive breast cancer between 1996 and 2007. They used the records to identify hormonal therapy prescriptions and refill dates. Each woman filled at least one prescription for tamoxifen or an aromatase inhibitor within one year of diagnosis.

The authors cited several possible reasons for halting therapy early, including the side effects of hormone therapy, difficulty remembering and medication costs. They cautioned that physicians may be unaware of compliance problems for their patients, and as more cancer treatments like oral chemotherapy and other drugs are increasingly taken at home, a clearer understanding of the reasons why patients do not complete their treatment is essential.

What This Means for Patients

The use of hormone therapy for hormone-sensitive breast cancers has been one of the most important additions to breast cancer treatment in recent decades. These drugs, which include tamoxifen and a class of medicines called aromatase inhibitors - all of which are taken orally - have significantly reduced cancer recurrences and deaths. Patients who are undergoing hormone therapy should talk to their doctors about therapy side effects and any problems associated with their medications prior to discontinuing.

Helpful Links from Cancer.Net:

• Guide to Breast Cancer [2]
• The Importance of Taking Your Medication Correctly [3]
• ASCO Expert Corner: Hormone Therapy Options for Early-Stage Breast Cancer [4]