Agreed that traction will be hard earned for Prolia, however, there are some serious advantages with the MOA of denosumab compared to bisphosphonates. The oncologists and orthopedists are just beginning to see the risks w zometa, etc re: BRONJ, long bone fractures, and femoral head necrosis.
While bisphosphonates have about a 10yr half-life, Prolia has a half-life of about 25 days (i am speaking from memory here). While BRONJ risk was actually higher for Xgeva vs Zometa on study, the theory is that denosumab (Xgeva, bony cancer) will offer potential of a drug holiday of about 1yr for the activity of osteoclasts to return to baseline. This is not the case w bisphosphonates. There is a very real 3-9% risk of BRONJ post-dental extraction due to lack of bony turnover. While this can be avoided w dental "cancer consults" prior to tx, remaining dentition will be subjected to reduced salivary flow and neglect that often accompanies chemo/radiation therapy.
While I agree that the economics of denosumab uptake will be challenging, I think that Xgeva will eventually eat into Zometa's mkt share. Additionally, I think that oral bisphosphonate use will begin to be limited to <5yrs on drug and then a several yr long drug holiday will be used as the bone is actually maintained very well without add'l dosing. See JAMA study in 2006... 19% fracture rate for this methodology vs 18.9% fracture rate for continuous dosing over 10yrs.
Look for something like Prolia and Reclast to take share away from oral drugs in osteoporosis. Docs get paid for the in-office procedure w both, being IV infusion q12mo w Reclast or subQ w Prolia. There also hasn't been the risk of BRONJ w Reclast like has been seen w Zometa.
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