ipg, if you stop cells from replicating they don't have the chance misfold to become cancerous. So, theoretically increasing bone building could have increased random cancer risk, to honor your point.
The black box for cancer of the bone with Tymlos and Forteo , though, was based on the rats used in the preclinical. These poor Fisker rats were found to get cancer even without parathyroid supplement. They were given the drug in multiples of the amounts given to humans.
The black box was imposed because of the flaw in their genetics, but was lifted because 20+ years of two years of use didn't cause cancer in humans. It wasn't lifted because of any study on extended use.
As normahorn reminds us, real world trials pretty firmly eliminate those whom the black box would exclude.
Your questioning is good because we don't have anything on extended use.
The science we have on teriparatide doesn't indicate cumulative risk. The hormone doesn't collect in your body but works afresh with each injection depending on washout before the next injection.
I shouldn't advise as I may have a few blind spots, but I can tell you how I'm laying my bets.
My plan is to stay on Forteo. I think it is the best osteoporosis medication out there. And just luckily, it's without sided effects for me. Forteo isn't giving me great BMD, but I'm not looking for heavy bones. I'm watching bone markers. If they eventually indicate greater bone loss, I'll stop the medication for a month and then resume the injections. If that proves ineffective, I'll take risidronate for 1 to 3 months, all while watching bone markers. If I had to run the bases bisphosphonates, Evenity, Prolia, I would. But my intention is to always return to home base on Forteo.