Is denosumab “better” than Zometa at preventing skeletal events?


Amgen, the developer of denosumab (also known as RANK-L) has released data today from a head-to-head trial of their drug vs. zoledronate (Zometa) in the management of patients with advanced breast cancer and bone metastases.

Although these are not data from prostate cancer patients, historic experience has shown that drugs like zoledronate and denosumab tend to have similar effects in the management of “skeletal-related events” (SREs) in patients with either breast cancer or prostate cancer. It is expected that denosumab will be approved for clinical use in patients with both types of cancer later this year, so it is worth being aware of what we can learn from the data provided in this study and made available today. (We expect that the full trial data will be presented at a major breast cancer meeting later in the year — perhaps that the annual San Antonio Breast Cancer meeting.

What the study appears to have shown is as follows:

  • Denosumab appears to extend the time to the first on-study SRE (a fracture, need for radiotherapy to the bone, surgey to the bone, or spinal cord compression) by about 18 percent compared to zoledronate.
  • It also appears to extend the time to first and later SREs by about 23 percent.

However,

  • Denosumab and zoledronate, in this trial, were both associated with the same, small degree of risk for osteonecrosis of the jaw (ONJ)
  • Denosumab and zoledronate were also both associated with similar levels of risk for adverse infectious events.
  • There was no difference in the overall survival or the time to disease progression of patients in the two arms of the trial.

What is the take-away here for prostate cancer patients? Probably two things:

  • Denosumab may turn out to be slightly slightly more effective than zoledronate in preventing SREs in patients on long-term hormone therapy for prostate cancer.
  • Denosumab seems to have the same level of risk as zoledronate for occurrence of ONJ (although it had been hoped that this side effect might be less common in patients treated with denosumab compared to those treated with zoledronate).

Clearly one should not assume that the same precise results will be seen in prostate cancer patients as in breast cancer patients, but these data do at least tell us what it might be reasonable to expect in prostate cancer patients — particularly that patienmts and their doctors will still need to be on their guard for any indications of or risk factors for ONJ.

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