RADIOSURGERY

• It uses a highly focused and precisely targeted radiation to the target tissue while minimizing the exposure to adjacent structure.
• The main aim is to long term arrest of tumour growth.
• Radiosurgery differs fundamentally from radiotherapy in that it delivers a single high dose of radiation rather than as a fractionated course or dose.
• Source: 201 cobalt (Gamma knife)
• Efficacy: 20 Gy in single fraction= 50-110 Gy in doses( in fractions)

ADVANTAGE:

1. It can be done in LA.
2. It is painless like having another scan.
3. It causes less damage to surrounding tissue.
4. It has low morbidty e.g. less incidence of FN palsy but more chances of hearing preservation.

USES:

1. Slow growing tumour: VS, meningioma, glomus, angiofibroma.
2. Thrombo-obliterative effect of radiosurgery for vascular tumour eg hemangiopericytoma and endolymphatic sac adenocarcinoma.
3. Limited control of chrdoma and chondrosarcoma.
4. As a booster dose or adjuvant to surgery or radiotherapy for NPC, SCC of skull base.

LIMITATIONS:

1. It is unsuitable for larger tumour >3 cm
2. Disease extending to neck as machine are designed for cranial disease
3. Risk of radiation: high dose may cause malignant transformation
4. Peritumoural scarring causing subsequent surgery difficult
5. Tumour continues to grow in 20 % so life long monitoring is necessary.

RADIOSURGICAL TECHNIQUE:

• Gamma technique
• Cyberknife
• LINAC
• Proton beam