2. Pituitary Irradiation Questions What are the indications for radiotherapy ? What does conventional radiotherapy involve? Radiosurgery ? What is stereotactic linear accelerator based radiotherapy ?
9. Results 90% control of Pituitary tumour at 10 years following surgery and radiotherapy
10. Visible tumour Gross Tumour Volume (GTV) GTV plus Normal tissue containing microscopic disease Clinical Target Volume (CTV) CTV plus Further tissue to allow for organ movement, set up Planning Target Volume (PTV) Radiotherapy Planning
15. Intention is to reduce the set up margin by more rigid immobilisation and conforming beams. Field size restricted to smaller fields Main indication when the subclinical invasion is minmal Benign, AVM, or only treating GTV Stereotactic Radiotherapy
16. Stereotactic Radiotherapy Precise positioning in three-dimensional space. In stereotactic surgery, a system of three-dimensional coordinates is used to locate the site to be operated on. In stereotactic radiotherapy, a system of three-dimensional coordinates is used to locate the site to be irradiated by a number of precisely aimed beams of ionizing radiation from diverse directions meeting at a specific point.
20. Single fraction Ablative dose Use for lesions where there is no significant subclinical spread. Small fields 4cm or less Immobilisation imperative Examples AVM Acoustic neuromas Meningiomas Metastases Stereotactic Radiosurgery
22. Multiple conventional fractions exploits reduced patient movement to reduce morbidity Use for lesions where there is minimal subclinical spread or as a boost to GTV only Immobilisation device must allow for repositioning daily Examples Pituitary tumours Meningiomas Gliomas (needs further studies) Stereotactic Linear accelerator based Radiotherapy
23. Conventional Radiotherapy Plan unavoidable dose to normal structures outside target volume Intensity Modulated Radiotherapy (I.M.R.T.)
24. Multiple beams, non uniform dose across the beam Intensity Modulated Radiotherapy (I.M.R.T.)
25. Radiotherapy Side Effects During Tired, Hair loss, tumour swell 2 months Somnolence, Recurrent symptoms: recurrence, necrosis or tumour swell 6 months Late radiation necrosis 2 years Intellectual deterioration
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27. Late Effects Tumourigenesis Some studies find patients who have had standard pituitary radiation therapy are at a 9.4- to 16-fold increased risk for malignant brain tumours (such as astrocytomas or gliomas) in comparison with the risk in the general population.
28. Pituitary Irradiation Summary Indications Conventional vs more technical radiotherapy Side effects usually rare and manageable