Insofar as metastatic prostate cancer is terminal and a large proportion of the deaths come from skeletal events and their complications (such as VTE), the boundary between treating the cancer and treating/preventing the bone mets is not well defined, IMO.
It clearly doesn't sound like the boundary is well-defined. One of the callers tried to bridge the gap by asking the doctor if any of the previously approved disease modifying drugs for HRPC showed a correlation between an improvement in bone scans and survival. There was a bit of a pause but I believe the doctor indicated that the disease-modifying drugs have never shown improvements in bone scans.
The best I can gather from listening to the calls is that the company and investigator are indicating that a HRPC patient will most of the time die due to bone metastases. But, in the absence of bone metastases (presumably due to a bone-targeted drug like denosumab), the HRPC patient will still die from the soft tissue cancer. And EXEL is hoping that 184 will be effective in both instances.