The Food and Drug Administration ( FDA ) has expanded the use of Xgeva ( Denosumab ) to treat adults and some adolescents with giant cell tumor of the bone ( GCTB ), a rare and usually non-cancerous tumor.

Giant cell tumor of the bone generally occurs in adults between the ages of 20 and 40 years. In most cases, GCTB 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 maintenance of healthy bone. RANKL is also present in GCTB. Xgeva is intended for patients whose GCTB cannot be surgically removed ( unresectable ) or when surgery is likely to result in severe morbidity, such as loss of limbs or joint removal. It should only be used in adolescents whose bones have matured.

The FDA reviewed Xgeva under its priority review program, which provides for an expedited review of drugs. Xgeva was granted orphan product designation because it is intended to treat a rare disease or condition.

The safety and effectiveness of Xgeva for giant cell tumor of the bone were established in two clinical trials that enrolled a total of 305 adult or adolescent patients. All patients had confirmed cases of GCTB that were recurrent, unresectable or where surgery would result in severe morbidity.

Of the 187 patients whose tumors could be measured, 47 patients had their tumors reduce in size after an average of three months. Over an average follow-up duration of 20 months, re-growth of giant cell tumor of the bone occurred in three patients whose tumors originally became smaller during treatment.

Common side effects included joint pain ( arthralgia ), headache, nausea, fatigue, back pain and extremity pain. The most common serious side effects were osteonecrosis ( areas of dead bone ) of the jaw and osteomyelitis ( inflammation or infection of the bone ).

Women of reproductive potential should use highly effective contraception while taking Xgeva because of potential fetal harm.

Xgeva was approved in 2010 to prevent fractures when cancer has spread to the bones.

Source: FDA, 2013

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