windyshores,
I'm not thinking there will ever be such a link. No one will conduct studies.
The FDA approved Tymlos on the basis of one clinical trial. The suspicion of osteosarcoma was directed from the Forteo rats and the two year limit was because of that caution. It remains in the Forteo insert that Forteo should only be given for more than two years in select patients likely to benefit, i.e., those with high fracture risk.
One doctor told me that the third year is similar to off label use, another said that he almost never prescribes medicines as recommended in inserts. He thinks the doses are often too high for women of little weight.