Denosumab Superior to Zoledronic Acid in Reducing Incidence of Skeletal-Related Events in Breast Cancer Patients with Bone Metastases

Data Presented at earlier this month at the San Antonio Breast Cancer Symposium demonstrates that treatment with denosumab, a new drug in late stage clinical development, is superior to the standard of care in advanced breast cancer patients. Among patients with bone metastasis from breast cancer, denosumab was superior to zoledronic acid in reducing the incidence of complications from bone metastases.

"Denosumab prevented more events, was better tolerated and is more convenient for patients," said Alison Stopeck, M.D., associate professor of medicine at the University of Arizona Cancer Center who presented the results of this phase III, double blind study at the 2009 CTRC-AACR San Antonio Breast Cancer Symposium.

Stopeck and colleagues enrolled 2,048 patients with bone metastasis who had never received treatment with intravenous bisphosphonates. They randomly assigned patients to treatment with 120 mg subcutaneous denosumab (Amgen) or 4 mg intravenous zoledronic acid (Zometa, Novartis) every four weeks.

Denosumab, is an investigational first fully human monoclonal antibody developed by Amgen. It works differently from existing bone treatments by specifically targeting a protein called RANK Ligand (RANKL), which plays an important role in regulating osteoclast activity and function and has been linked with increased bone loss and complications from bone metastases.

Stopeck presented data confirming that denosumab significantly delayed time to first on-study skeletal-related event compared with zoledronic acid (HR=0.82; 95% CI, 0.71-0.95), as well as time to first, and subsequent, on-study skeletal-related event (rate ratio=0.77; 95% CI, 0.66-0.89). In this study, patients assigned to denosumab had 491 skeletal-related events compared with 623 for patients assigned to zoledronic acid.

"In clinical trials testing new medications for bone metastases, treatment success is measured by whether the bone complications, or skeletal related events, caused by the tumor are reduced or delayed," Stopeck explained. "Skeletal complications from bone metastases are a critical and painful health concern for patients with advanced breast cancer, and can increase the risk of mortality. Patients who have a first skeletal related event are twice as likely to experience a subsequent SRE, so it is imperative to treat these advanced breast cancer patients."

“Denosumab resulted in a considerable delay in the development of moderate-to-severe pain compared to zoledronic acid,” Stopeck said.

Additional data from this study showed that denosumab significantly reduced the mean annual skeletal morbidity rate (SMR) (the ratio of the number of skeletal complications to the time on trial) compared with Zometa (0.45 vs. 0.58, respectively; p=0.004).

Overall, the incidence of adverse events (96% denosumab, 97% zoledronic acid) and serious adverse events (44% denosumab, 46% zoledronic acid) was consistent with what has previously been reported for these two agents. Adverse events potentially associated with acute phase reactions during the first three days of the study were reported in 10.4 percent of the denosumab arm and 27.3% of the zoledronic acid arm. Adverse events potentially associated with renal toxicity occurred in 4.9% of patients treated with denosumab compared to 8.5% in patients treated with zoledronic acid.

Osteonecrosis of the jaw (ONJ) was seen infrequently in both treatment groups (20 patients receiving denosumab [2.0%] as compared with 14 patients [1.4%t] receiving Zometa). Rates of new primary malignancies were similar between treatment arms (5 patients receiving denosumab [0.5%] and 5 receiving zoledronic acid [0.5%]). Time to disease progression or overall survival was balanced between the study arms.

At 34 months, 30.7% of patients treated with denosumab arm experienced at least one skeletal-related event (95% CI, 33.5%-39.4%) compared with 36.5% of those treated with zoledronic acid. Denosumab also reduced mean skeletal morbidity rate (0.45 vs. 0.58; P=.004).

Clinical relevance
Bone metastases, cancer cells that separate from tumors and migrate to bone tissue where they settle and grow, occur in more than 1.5 million people worldwide. With improvements in cancer care, including earlier diagnosis and new treatment options, leading to increases in survival rates, the number of patients developing metastatic disease secondary to a primary cancer is increasing. Bone metastases are a significant problem for patients with certain types of advanced cancer, with incidence rates of nearly 100 percent in myeloma patients and as high as 75 percent in breast and prostate cancer patients.

With bone metastases the growing cancer cells weaken and destroy the bone around the tumor. The damage the tumor has caused to the bone can result in a number of serious complications, collectively called SREs. These include fracture of a bone, the need for radiation to bone, the need for bone surgery, or spinal cord compression. All are serious complications for advanced cancer patients.

The economic burden of United States (U.S.) patients with bone metastases is significant and was estimated to be $12.6 billion last year. Patients with bone metastases who experience an SRE incur significantly higher medical costs compared with those who do not experience an SRE.

The results of this study are therefore clinically relevant. Before the availability of bisphosphonates 64% patients with breast cancer with bone metastases generally developed a skeletal-related event, including fracture or pain. With the introduction of Bisphosphonates, this was reduced this to 43%. Today, with more potent agents such as zoledronic acid, the development of skeletal-related event are less than 34%. The results of this trial comparing denosumab vs zoledronic acid shows further improvement with a 27% reduction of incidence rate.

This oral presentation of the denosumab 136 data by Dr. Alison Stopeck was presented at the 2009 CTRC-AACR San Antonio Breast Cancer Symposium. on Thursday, December 10 at 3:15 PM (CT) in Exhibit Hall D of the Henry B. Gonzalez Convention Center, San Antonio, Texas.

For more information

• Downey L, Livingstone R, Stopeck A. Diagnosing and treating breast cancer in elderly women: a call for improved understanding. J Am Geriatr Soc 2007 Oct;55(10):1636-44. Epub 2007 Aug 28.
• Coleman R. Potential use of bisphosphonates in the prevention of metastases in early-stage breast cancer. Clin Breast Cancer 2007 Jul;7 Suppl 1:S29-35
• Coleman R. On the horizon: can bisphosphonates prevent bone metastases? Breast. 2007 Dec;16 Suppl 3:S21-7. Epub 2007 Nov 7. Review.
• Coleman RE. The benefits and costs of bisphosphonates. J Support Oncol 2007 Nov-Dec;5(10):483-4.
• Brown JE, Coleman RE. The present and future role of bisphosphonates in the management of patients with breast cancer. Breast Cancer Res. 2002;4(1):24-9. Epub 2001 Nov 26. Review.
• Rosen LS, Gordon D, Kaminski M, Howell A, Belch A, et al. Zoledronic acid versus pamidronate in the treatment of skeletal metastases in patients with breast cancer or osteolytic lesions of multiple myeloma: a phase III, double-blind, comparative trial. Cancer J. 2001 Sep-Oct;7(5):377-87.
• Coleman RE. Metastatic bone disease: clinical features, pathophysiology and treatment strategies. Cancer Treat Rev. 2001 Jun;27(3):165-76. Review.
• Capanna R, Coia LR, Coleman R. et al. eds. Textbook of Bone Metastases Hoboken, NJ: Edition: John Wiley and Sons; 2005:105.
• Mundy GR. Metastasis to bone: causes, consequences and therapeutic opportunities. Nat Rev Cancer. 2002 Aug;2(8):584-93. Review
• Schulman KL, Kohles J. Economic burden of metastatic bone disease in the U.S. Cancer. 2007 Jun 1;109(11):2334-42.
• Mortimer JE, Schulman K, Kohles JD. Patterns of bisphosphonate use in the United States in the treatment of metastatic bone disease. Clin Breast Cancer. 2007 Aug;7(9):682-9.

Also follow

• Onco'Zine - The International Cancer Network

Bisphosphonates and the Risk of Postmenopausal Breast Cancer

Bisphosphonates are routinely given to women with postmenopausal breast cancer, but new data suggest that these agents may play an important role in reducing recurrent breast cancer as well. Results of a new trial demonstrated that the use of bisphosphonates was associated with a 29% reduction in the risk of postmenopausal breast cancer. The results were presented at the CTRC-AACR San Antonio Breast Cancer Symposium.

Link between Bisphosphonates and Breast Cancer
When breast cancer metastasizes, it often spreads first to the bones. Bone metastases can lead to complications such as pain, fractures, spinal cord compression, bone marrow suppression, and hypercalcemia. The primary reason for this link is that breast cancer cells stimulate bone cells called osteoclasts, and these osteoclasts in turn stimulate the growth of breast cancer cells.

Bisphosphonates have emerged as a highly effective therapeutic option for the prevention of skeletal complications secondary to bone metastases. They interrupt the relationship between osteoclasts and breast cancer cells in early stage breast cancer, slowing the progression of bone metastases while, at the same time, reducing the skeletal complications in women with metastatic breast cancer. Research has also demonstrated that bisphosphonates may prevent the development of bone metastases in newly diagnosed patients with no evidence of metastasis.

A number of agents are now approved in both Europe and the US. They included Clodronate, Pamidronate, Ibandronate, Zoledronic acid.

New and ongoing research
Lead researcher Gad Rennert, M.D., Ph.D., chairman of the Department of Community Medicine and Epidemiology at the Carmel Medical Center of Clalit Health Services and a faculty member at the Technion-Israel Institute of Technology in Israel, said these data help shed light on a possible new pathway for breast cancer prevention.

"We have identified a new class of drugs that is associated with a reduced risk of breast cancer, and if proven in randomized trials, we may be able to recommend it to postmenopausal women for this purpose," said Rennert.

Rennert and colleagues extracted data from the Breast Cancer in Northern Israel Study, which is a population-based, case-control study. They evaluated the use of bisphosphonates for at least five years in 4,575 postmenopausal study participants using a structured interview. The self-reported, long-term use of bisphosphonates prior to diagnosis was associated with a significant reduced relative risk for breast cancer by approximately 34%.

This reduction remained significant, at 29%, even after adjusting for a large variety of risk factors for breast cancer such as age, fruit and vegetable consumption, sports activity, family history of breast cancer, ethnic group, body mass index, calcium supplement and hormone replacement therapy use, number of pregnancies, months of breastfeeding and age at first pregnancy.

Moreover, the breast tumors identified among patients who used bisphosphonates were more often estrogen receptor positive and less often poorly differentiated.

"These tumors are the type that are associated with a better prognosis," said Rennert.

While most experts are cautiously optimistic about the results of this study, several of them said that more information is necessary, and as of now, they would not suggest the use of bisphosphonates for women who do not have osteoporosis.

For more information:

• Coleman RE. Bisphosphonates in breast cancer. Ann Oncol 2005 May;16(5):687-95. Epub 2005 Mar 31.
• Logman JF, Heeg BM, Botteman MF, Kaura S, van Hout BA. Economic evaluation of zoledronic acid for the prevention of osteoporotic fractures in postmenopausal women with early-stage breast cancer receiving aromatase inhibitors in the UK. Ann Oncol. 2009 Dec 2. [Epub ahead of print]
• Ghazi M, Roux C. Hormonal deprivation therapy-induced osteoporosis in postmenopausal women with breast cancer. Best Pract Res Clin Rheumatol. 2009 Dec;23(6):805-11.
• Theriault RL. Bisphosphonates: ready for use as adjuvant therapy of breast cancer? Curr Opin Obstet Gynecol. 2009 Nov 19. [Epub ahead of print]

Also see:

• Onco'Zine - The International cancer Blog