Is teriparatide (parathyroid hormone-related protein) safe for a hypogonadal man with a history of Craniopharyngioma treated with surgery and radiotherapy?

Teriparatide is Contraindicated in Patients with Prior Radiation Therapy to the Skeleton

Teriparatide should not be used in a hypogonadal man with history of craniopharyngioma treated with surgery and radiotherapy due to the absolute contraindication in patients with prior radiation therapy involving the skeleton. 1

Contraindications for Teriparatide

• Teriparatide is explicitly contraindicated in patients with "prior external beam or implant radiation therapy involving the skeleton" according to FDA labeling 1
• The contraindication exists due to potential increased risk of osteosarcoma in patients with risk factors such as prior radiation therapy 1, 2
• This applies directly to patients with craniopharyngioma who received cranial radiotherapy, as this involves radiation to the skeletal structures of the skull 1

Risks Associated with Craniopharyngioma and Radiotherapy

• Radiotherapy for pituitary tumors and craniopharyngioma is associated with significant long-term risks, including:

  • Development of hypopituitarism in up to 80% of patients by 10-15 years post-radiotherapy 2
  • Increased risk of secondary brain tumors, particularly in younger patients 2
  • Higher risk of developing meningiomas (standardized incidence ratio of 658) after cranial radiotherapy 2

• The risk of developing secondary malignancies is significantly higher in patients who received radiotherapy at a younger age:

  • 2.4-fold increased risk of malignant brain tumors for every 10 years of younger age 2
  • 1.6-fold increased risk of meningioma for every 10 years of younger age 2

Alternative Treatment Considerations

• Bisphosphonates are considered the preferred treatment option for osteoporosis in patients with a history of malignancy 2
• For patients with craniopharyngioma specifically:
  • Close monitoring for tumor recurrence is essential, with MRI surveillance recommended at 3 and 6 months, and 1,2,3, and 5 years after surgery 2
  • Long-term follow-up for hypopituitarism needs to be lifelong, with planned transition to specialist adult services 2

Clinical Evidence on Teriparatide and Radiation

• While a recent study involving 200,000 patients showed no significant difference in osteosarcoma incidence between teriparatide-treated patients and the general population, this study did not specifically address patients with prior radiation therapy 2
• Case reports exist of teriparatide use in patients with prior radiotherapy, but these represent exceptional circumstances where other treatment options were exhausted 3
• The FDA contraindication remains in place despite these reports, indicating that the theoretical risk is still considered significant 1

Mechanism of Concern

• Teriparatide works by increasing bone turnover through sequential increase in bone resorption followed by formation 2
• This increased bone turnover may theoretically promote propagation of microscopic bone metastases or secondary malignancies through:
  • Liberation of bone-derived growth factors and cytokines 2
  • Potential direct anabolic effects on tumor cells 2
• These mechanisms are particularly concerning in patients already at increased risk due to prior radiation exposure 2, 1

In conclusion, despite the potential benefits for treating osteoporosis, teriparatide is absolutely contraindicated in this patient due to their history of cranial radiotherapy for craniopharyngioma. Alternative osteoporosis treatments should be pursued.