Radiotherapy in Aggressive or Dopamine Agonists Resistant Prolactinomas; is It Still Worthwhile?

Radiotherapy, conventional or radiosurgery, has been used to control prolactin secretion and tumour growth in prolactinomas both as part of multimodal therapy or rarely as primary treatment. However, considering the radiotherapy side effects, notably hypopituitarism, as opposed to the high efficacy and low toxicity of dopamine agonists (DA) treatment and neurosurgery, radiotherapy is recommended mostly for patients with aggressive or high-risk prolactinomas or in those resistant or intolerant to medical therapy, usually after surgical failure. We provide an overview of the published literature on the efficacy and toxicity of radiotherapy (conventional fractionated or radiosurgery), in aggressive, high-risk, or DA resistant prolactinomas. Radiotherapy has shown a good efficacy and a reasonable toxicity profile in prolactinomas where other treatment modalities failed. In aggressive and high-risk prolactinomas, the cumulative percentage for tumour control (reduction plus stable) ranged from 68% to 100%. Most studies reported global hormonal control rates over 50%. In resistant prolactinomas, the global secretion control rate (on, but also off DA) ranged from 28% to 89%-100%; in most studies over 80%. The 5-year rate of hypopituitarism was around 12%-25%. To date there are no controlled study on the use of radiotherapy as a prophylactic treatment in patients with clinical, radiological or pathological markers of aggressiveness. In conclusion, our review supports the use of radiotherapy in patients with growing, clinically aggressive or truly DA resistant prolactinomas. In patients with high-risk or invasive prolactinomas or in those harboring pathological markers of aggressiveness, the prophylactic use of radiotherapy should be individualized.