Prolia Reduces Recurrence Risk of Hormone-Receptor-Positive Disease in Women Taking Aromatase Inhibitors

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Prolia (chemical name: denosumab) is a targeted therapy used to treat bone loss in women taking aromatase inhibitors as part of their breast cancer treatment. Prolia is given as an injection under the skin every 6 months at a dose of 60 mg.

A study has found that Prolia improved disease-free survival for postmenopausal women diagnosed with early-stage, hormone-receptor-positive breast cancer taking an aromatase inhibitor.

Disease-free survival is how long a woman lives without the cancer coming back (recurring).

The study, “The Impact of Adjuvant Denosumab on Disease-Free Survival: Results from 3,425 Postmenopausal Patients of the ABCSG-18 Trial,” was presented on Dec. 9, 2015 at the 2015 San Antonio Breast Cancer Symposium.

Marisa Weiss, M.D., Breastcancer.org chief medical officer, discusses this study:

Aromatase inhibitors are hormonal therapy medicines often used to treat postmenopausal women diagnosed with hormone-receptor-positive breast cancer after surgery to reduce the risk of the cancer coming back (recurrence).

The aromatase inhibitors are:

  • Arimidex (chemical name: anastrozole)
  • Aromasin (chemical name: exemestane)
  • Femara (chemical name: letrozole)

Hormonal therapy given after surgery is called adjuvant hormonal therapy.

Hot flashes, night sweats, and joint pain are common side effects of aromatase inhibitors. These medicines also can weaken bones over time and increase chances of breaking a bone. So it makes sense to use medicine and other steps to strengthen bones while taking an aromatase inhibitor.

Prolia also is used to treat postmenopausal women diagnosed with osteoporosis at high risk of breaking a bone or who haven’t gotten any benefits from other osteoporosis medicines.

Denosumab is also branded as Xgeva, which is approved to reduce the risk of bone complications (such as fracture) and bone pain caused by advanced-stage cancers, including breast cancer, that have spread to bone. Xgeva is given as an injection under the skin every 4 weeks at a dose of 120 mg.

Denosumab is a targeted therapy, which means it targets specific characteristics of cells. Some targeted therapies, including denosumab, are antibodies that work like the antibodies made naturally by the immune system. Denosumab targets a protein called RANK ligand (RANKL). RANKL affects the activity of certain bone cells called osteoclasts. Osteoclasts help with normal bone breakdown activity to regulate calcium levels. Denosumab blocks RANKL activity and limits osteoclast activity. So denosumab treats osteoporosis by restoring a healthier balance of bone building and bone breakdown. In women who have been diagnosed with breast cancer that has spread to bone, osteoclasts tend to be overactive. These overactive osteoclasts can cause bone pain and bone destruction. By blocking the RANKL protein, denosumab lowers the activity level of the osteoclasts in women whose cancer has spread to bone, reducing their risk of pain and other bone complications.

In the ABCSG-18 study, 3,425 postmenopausal women diagnosed with early-stage, hormone-receptor-positive breast cancer who were taking an aromatase inhibitor were randomly assigned to get either:

  • an injection of 60 mg of Prolia every 6 months
  • an placebo injection every 6 months of a substance that looked just like Prolia

The women got the Prolia or placebo injections for 3 years.

Earlier results from the ABCSG-18 study found that Prolia reduce the risk of breaking a bone by 50% in postmenopausal women diagnosed with early-stage, hormone-receptor-positive breast cancer who were taking an aromatase inhibitor.

In this new analysis, the researchers wanted to know if Prolia also could help reduce the risk of breast cancer recurrence.

After about 4 years of follow-up, the researchers found that women who were being treated with Prolia had an 18% lower risk of recurrence than women who were being treated with the placebo. This is about a 2% absolute reduction in risk.

“Our new data suggest that this treatment should be offered to all patients with hormone-receptor-positive breast cancer who are receiving adjuvant aromatase inhibitor therapy, irrespective of their bone health status,” said Michael Gnant, M.D., professor of surgery at the Medical University of Vienna.

Possible side effects of Prolia include back, arm, and leg pain; high cholesterol levels; and urinary infections. More serious but much less common side effects include low blood calcium levels, rashes, and severe infections. In rare cases Prolia can cause breakdown of the jaw bone (called osteonecrosis of the jaw).

In this study, Prolia caused no severe side effects and none of the women developed osteonecrosis of the jaw.

If you’re a postmenopausal woman who’s been diagnosed with early-stage, hormone-receptor-positive breast cancer and will be taking an aromatase inhibitor after surgery, you might want to talk to your doctor about this study and ask whether Prolia could possibly reduce the risk of recurrence while keeping your bones strong.

Visit the Bone Health section of Breastcancer.org to learn more about the steps you can take to keep your bones strong during and after breast cancer treatment. In this section, you can learn about diet and lifestyle changes for maintaining bone health, as well as bone strengthening medicines.

Read more Research News from the 2015 San Antonio Breast Cancer Symposium:



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