Radiation therapy is generally reserved for patients in whom both surgical and medical interventions have not provided biochemical control (1).

• reduces growth hormone concentrations in 90% of patients
  
  
• prevents regrowth of the tumour in 99%
  
  
• possible complications include:
  • hypopituitarism:
    • commonest side effect
    • about half of patients may require replacement for adrenocorticotrophin hormone, thyroid stimulating hormone, or gonadotrophin deficiency by 10 years
  • visual loss
  • brain necrosis
  • tumorigenesis

Notes:

• stereotactic radiosurgery techniques have advantages over conventional fractionated radiotherapy
  • better targeting and reduced radiation exposure to surrounding tissue and shorter time to achieve control of IGF-1 and GH levels
  • extremely large tumor volumes or tumors near the chiasm are not amenable to radiosurgery - therefore such cases require fractionated radiotherapy
  • with either fractionated radiotherapy or radiosurgery
    • may take many years to achieve the full therapeutic effect and continued medical treatment will usually be needed.

Reference:

• Adelman DT et al. Acromegaly: the disease, its impact on patients, and managing the burden of long-term treatment.Int J Gen Med. 2013;6:31-8
• Editorial.Acromegaly:treatment after 100 years. BMJ 2000;307: 1505-6.