Extended adjuvant therapy in hormone-receptor-positive early breast cancer

This review examined the benefits of extending hormone therapy from 5 to 10 years in patients with hormone receptor positive breast cancer. The study concluded that treatment recommendations should take factors such as previous treatments and potential side effects into account.

Hormone-receptor (HR)-positive breast cancer grows in response to female hormones (such as estrogen or progesterone). Adjuvant therapy (treatment after surgery) with tamoxifen (Nolvadex) for 5 years is standard for early stage HR positive breast cancer. Tamoxifen is a drug that blocks estrogen from binding to the estrogen receptors on the cancer cells, slowing tumor growth.

The risk of relapse in this type of breast cancer can persist for at least 15 years. Extended adjuvant endocrine therapy with tamoxifen or an aromatase inhibitor such as letrozole (Femara, blocks the production of estrogen) may improve survival outcomes or prevent late relapses.

This study reviewed clinical trials that assess the benefits of extending adjuvant therapy from 5 to 10 years.

In two large clinical studies, 10 years of tamoxifen therapy reduced the risk of relapse compared to patients receiving 5 years of therapy (25% reduced risk). However, there was also an 87% increased risk of developing blood clots in the arteries of the lung with extended treatment.

One study noted that patients treated with letrozole after tamoxifen therapy had a 43% decreased risk of cancer returning compared to those treated with placebo (substance with no active effect).

A fourth study included 1918 postmenopausal women already treated with 5 years of an aromatase inhibitor. Patients were randomly assigned to treatment with 5 years of letrozole or 5 years of placebo. Patients were followed for an average of 6.3 years. The risk of cancer returning was reduced by 33% in the group receiving letrozole compared to placebo. However, these patients were at an increased risk of bone fractures (14% of patients) compared to placebo (9% of patients).  

The authors concluded that continued hormone therapy may benefit some patients. They suggest that treatment recommendations should take into account previous treatments, potential side effects, and the potential benefits for the patient.

Speak to your doctor about the potential benefits of extended adjuvant therapy.