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Denosumab (Xgeva) Approved to Treat Bone Tumors
The FDA has expanded the approved use of denosumab (Xgeva, Amgen) to treat adults and some adolescents with giant cell tumor of the bone (GCTB), a rare and usually noncancerous tumor.
GCTB generally occurs in adults between the ages of 20 and 40 years. In most cases, the tumor does not spread to other parts of the body but destroys normal bone as it grows, causing pain, limited range of motion, and bone fractures. Rarely, GCTB can transform into a cancerous tumor and spread to the lungs.
Denosumab is a monoclonal antibody that binds to RANKL, a protein essential for the maintenance of healthy bone. RANKL is also present in GCTB. Denosumab is intended for patients whose GCTB is unresectable or when surgery is likely to result in severe morbidity, such as loss of limbs or joint removal. The drug should only be used in adolescents whose bones have matured.
The safety and effectiveness of denosumab for GCTB were established in two clinical trials that enrolled a total of 305 adult or adolescent patients. All of the patients had confirmed cases of GCTB that were recurrent or unresectable, or where surgery would result in severe morbidity.
Of the 187 patients whose tumors could be measured, 47 patients (25%) experienced reductions in the size of their tumors after an average of 3 months. Over an average follow-up period of 20 months, regrowth of GCTB occurred in three patients whose tumors originally became smaller during treatment.
Common side effects included arthralgia, headache, nausea, fatigue, back pain, and extremity pain. The most common serious side effects were osteonecrosis of the jaw and osteomyelitis.
Women of reproductive potential should use highly effective contraception while taking denosumab because of potential fetal harm.
Xgeva (denosumab) was approved in 2010 to prevent fractures when cancer has spread to the bones.
Source: FDA; June 13, 2013.