Aromatase Inhibitor (AI) Induced Arthralgias
What Is It?
Arthalgia (joint pain) is a symptom commonly seen in breast cancer patients
treated with aromatase inhibitors (AI). These medications are often prescribed
to postmenopausal women with ER-positive and/or PR-positive tumors. There
are three AIs in routine clinical use: Arimidex (anastrazole), Femara
(letrozole), and Aromasin (exemestane). They all have similar efficacy
and side effects. Patients usually present with morning stiffness and
joint discomfort in various sites, including hands, knees, back, hips,
and shoulders. There is usually no obvious change in the appearance of
the joints. The symptoms typically begin appearing at approximately 2
months after the start of treatment and peak at 6 months, but they can
appear up to 2 years after the initiation of therapy.
How Common Are They?
Arthralgias appear to affect up to 50% of women who take AI, with up to
15% of women experiencing symptoms so intense that they stop the medication.
Risk factors for the development of arthralgias include: previous hormone
therapy, previous chemotherapy, obesity, and history of joint pain.
What Causes Them?
The exact mechanism of AI-induced arthralgias is unknown. AI work by stopping
the production of estrogen in postmenopausal women. By lowering circulating
estrogen levels in the bloodstream, there is less available to stimulate
the growth of ER-positive breast cancer cells. Estrogen deficiency is
associated with the development of joint pain and estrogen deprivation
has been hypothesized as the major cause of AI-induced arthralgias.
Joint pain from taking an AI can be troubling. However, a 2008 British
study suggested that women who experienced joint pain while taking hormonal
therapy medicine were less likely to have the breast cancer come back (recur).
What Can Be Done for Them?
No study has focused on the optimal management of AI-induced arthralgia.
Combining regular exercise and maintenance of a healthy with other AI induced
arthralgia treatment strategies appears to work best.
SWOG 0212 is a nationwide clinical study currently available at the Huntington
Hospital studying the potential benefits of a medication for AI-induced
arthalgias. For more information about this study, please click