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Radiotherapy
- Considered as an adjunctive treatment in patients not fully responding to surgical or pharmacological therapy
- Should generally be reserved as third-line treatment in patients who have not achieved tumor growth control or normalization of hormone levels with surgery and/or medical therapy
- May also be used in patients receiving growth hormone receptor antagonist (who have failed other medical therapies) and are at risk of tumor growth
- Other endocrinologists have used radiotherapy in patients controlled on medical therapy to allow termination of such therapy (which is potentially lifelong)
- Conventional radiotherapy can normalize insulin-like growth factor-I and lower growth hormone levels in >60% of patients
- However, maximum response is achieved 10-15 years after administration of radiotherapy
- Medical therapy with somatostatin analogues is usually required during this latency period
- Choice of technique depends on tumor characteristics
- Conventional radiotherapy is preferred for large tumor remnants or tumors that are near to optic pathways
- Stereotactic radiotherapy is the choice for smaller tumor size or if convenience for patient is desired
- Main limitations of radiation therapy is safety, with hypopituitarism observed in >40% of patients
- Advise patients that serial pituitary function follow-up is needed to evaluate for hypopituitarism
- Follow-up includes assessment of thyroid, adrenal and gonadal functions at least annually
- Conventional radiotherapy may carry risk of second tumors or cerebrovascular events due to radiation vasculopathy
