Denosumab fortifies bone in breast cancer patients

By Lisa Baertlein

LOS ANGELES (Reuters) - The osteoporosis drug denosumab increased bone strength in women receiving hormone therapy for breast cancer, drug maker Amgen Inc said Friday.

The results of a phase III study of denosumab showed a 5.5-percent increase in bone strength in drug-treated patients after 12 months.

Amgen announced in July that the company-funded study showed denosumab strengthened bones thinned by estrogen-depleting breast cancer drugs known as aromatase inhibitors.

Researchers said denosumab, which is administered by injection twice a year, increased bone density in the spongy part of the bone. It also strengthened cortical bone, the dense outer shell of the skeleton that is responsible for the support and protective function of the skeleton, they said.

"In this study, denosumab data looks promising and, as a clinician, I look forward to having a potential alternative to existing therapies," said lead investigator Dr. Georgiana Kehr Ellis, from the oncology division at the University of Washington School of Medicine in Seattle.

The study involved 252 early-stage breast cancer patients who had below-average bone density, but had not progressed to osteoporosis. All of the participants were also required to take calcium and vitamin D daily.

Each of the women had bone loss in at least one of three sites: lumbar spine, total hip or femoral neck -- a common site of fractures where the ball at the top of the leg bone breaks off.

At 12 and 24 months, lumbar spine bone mineral density in the denosumab group increased 5.5 percent and 7.6 percent, respectively, compared with the placebo group.

Researchers said increases in bone density were consistently observed at 12 and 24 months at the total hip and total body, and at predominantly cortical sites at the femoral neck and distal radius, a common site of wrist fractures.

They also said the denosumab group's lumbar spine bone density at 12 months increased 4.8 percent, while the placebo group recorded a 0.7 percent decrease.

At 2 years, the lumbar spine bone density of women treated with denosumab was up 6.2 percent from the start of the trial versus a 1.4 percent decrease in the placebo group.

Nineteen women, or 15 percent, in the denosumab group experienced serious adverse effects, compared with 11, or 9 percent, in the placebo arm. None of the adverse events in either group were considered treatment-related.

Two deaths, one in each group, were reported in the study. Researchers said the deaths were not considered treatment-related.