"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
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- 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.
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