9 November 2017
In patients with a common form of breast cancer, known as estrogen receptor (ER) “positive”, endocrine therapy is often recommended after other treatments such as surgery, chemotherapy, and radiation are complete. Tamoxifen, most commonly used in pre-menopausal women, blocks the estrogen receptor on the breast cell, so estrogen cannot impact cell growth. In post-menopausal women, aromatase inhibitors (AI) are commonly used – these medications block the production of estrogen in the fat cells – a primary source of estrogen after menopause. Historically, these medications have been used for 5 years after completion of other treatment, although there are some studies suggesting longer courses may benefit certain patients. However, longer courses of therapy are associated with a higher incidence of side effects.
A study just published in the New England Journal of Medicine demonstrated that after 5 years of endocrine therapy, patients have an increasing risk of breast cancer recurrence with long term follow up. The authors evaluated individual patient data from a large database of randomized trials. They found that in patients with stage I tumors (tumor less than 2 centimeters and no lymph node involvement) the 20 year risk of recurrence was approximately 13%. In patients with 4-9 involved nodes, the risk ranged from 34-41% depending on the size of the main tumor.
This study is important as it confirms what many of us see in our practices – that breast cancer can and does recur, even many years after therapy. However, it also raises an important discussion point about our treatments. Studies have estimated that as many as 30% of women prescribed endocrine therapy stop treatment due to side effects which significantly interfere with quality of life such as menopausal symptoms, bone and joint pains, bone loss (osteoporosis) and fracture, and mental status changes (“chemobrain”). Patients should discuss any of these symptoms, especially if they are considering stopping their medication, with their physicians. Lifestyle changes, exercise programs, and medications may be of benefit. It is also important to understand that despite all appropriate treatment, cancer can and does come back – so health maintenance and surveillance are important even long after cancer therapy has ended.