How do you approach counseling patients on the use of low-dose radiation therapy (LDRT) for osteoarthritis who are concurrently receiving parathyroid hormone (PTH) anabolic treatment?  

Historically, teriparatide and other PTH anabolic agents carried a boxed warning against use in patients with a history of external beam radiation therapy due to concerns about osteosarcoma risk. However, extensive post-marketing surveillance and long-term observational studies have shown no increased incidence of osteosarcoma in humans treated with teriparatide. Based on this evidence, the FDA removed the boxed warning from teriparatide’s label in November 2020. Similarly, abaloparatide (Tymlos) had its boxed warning removed in December 2021 following comparable data.

While these changes reflect a shift in safety perception regarding prior radiation exposure, I have been unable to find specific guidance or contraindications related to the concurrent or sequential use of low-dose radiation therapy (LDRT) and PTH anabolic agents. This question was raised by a rheumatologist, and although LDRT is increasingly used for non-oncologic indications such as osteoarthritis, there is currently no clear evidence or regulatory guidance addressing its compatibility with PTH anabolics