The joint and muscle pain associated with some breast cancer treatment drugs may soon be a thing of the past so long as patients get enough vitamin D.

A new study out of the Washington University in St. Louis School of Medicine found that weekly doses of vitamin D may help ease the painful side effects of aromatase inhibitors.

Aromatase inhibitors are used to shrink breast tumors caused by estrogen. According to a news release about the study, doctors often prescribe these drugs in place of chemotherapy due to their lower toxicity and their ability to limit cancer recurrences. But, patients who use the aromatase inhibitors report discomfort and pain in their hands, wrists, knees, hips, lower back, shoulders and feet.

Dr. Antonella L. Rastelli, assistant professor of medicine and first author of the study, said in the news release that about half of the patients taking aromatase inhibitors can experience these symptoms.

“We don’t know exactly why the pain occurs, but it can be very debilitating — to the point that patients decide to stop taking aromatase inhibitors,” she stated.

Rastelli conducted a study of 60 people who take anastrozole, an FDA-approved aromatase inhibitor and had low levels of vitamin D.

Thirty patients were assigned the recommended daily dose of vitamin D (400 international units) and a 50,000-unit vitamin D capsule once a week.

The other half of the group was assigned the daily dose of vitamin D and a placebo.

All study participants were also given 1,000 milligrams of calcium.

Patients then filled out surveys to indicate their pain levels throughout the week. Those patients who received the high-dose vitamin D every week reported significantly lower pain levels.

“Patients who get the vitamin D weekly feel better because their pain is reduced and sometimes goes away completely,” Rastelli said in the news release. “This makes the drugs much more tolerable. Millions of women worldwide take aromatase inhibitor therapy, and we may have another ‘tool’ to help them remain on it longer.”

Rastelli believes that, based on the study’s findings, vitamin D may help patients who take the other two approved aromatase inhibitors, letrozole and exemestane.

The study was supported by Astra-Zeneca, which makes the aromatase inhibitor anastrozole under the brand name Arimidex.

The study was published in the online edition of Breast Cancer Research and Treatment.