Short course radiation therapy is one of the most talked about subject in recent years and also a fascinating research zone. Hypofractionated radiation therapy is an old concept, but only in recent years with tremendous improvement in radiation therapy delivery technologies, there is a significant visible surge in its applicability in clinical practice. Modern radiation therapy technology is capable of delivering high dose to the target while sparing majority of the adjacent critical structures. Hence, it is possible to deliver a short course of the treatment regimen with a higher dose per fraction without increasing toxicity. In brain tumours, radiosurgery with gamma-knife is considered standard of care in many of the clinical indications such as small meningiomas, acoustic schwannomas, residual low-grade gliomas, AVMs and solitary/ oligo brain metastasis. Gamma-knife radiosurgery is in clinical practice for more than five decades.
There are several prospective and randomized studies (level I evidence) with long-term follow up data supporting the use of radiosurgery in these clinical indications. Other indications of radiosurgery are pituitary tumour, craniopharyngiomas, glomus tumours, chordomas and others. Robotic radiosurgery (CyberKnife®) is precision radiosurgery delivery system and an extension of gamma-knife system. CyberKnife uses the principle of gamma-knife, but with linear accelerator source instead of multiple cobalt sources. CyberKnife is capable of treating all tumours indicated for gamma-knife with similar accuracy.
This modern tool has some additional advantages from gamma-knife, such as:
1) CyberKnife can use fractionated treatment, hence relatively larger tumours can be treated,
2) Require only thermoplastic mask, no need for an invasive frame,
3) Has an inverse planning system, can spare critical structure,
4) There is an ‘intra-fraction’ correction technology with imaging,
5) There is no need to change the source, hence may be more cost-effective and
6) Can be used to treat extra-cranial tumours also.
CyberKnife has a linear accelerator attached with a robot and is capable of treatment from various coplanar and non-coplanar field arrangements. CyberKnife has sub-millimetre accuracy and unmatched dose distribution.
The advanced technology behind CyberKnife uses image guidance technology and computer-controlled robotics to deliver an extremely precise dose of radiation to targets, avoiding the surrounding healthy tissue, and adjusting for patient and tumor movement during treatment. In conclusion, CyberKnife is an extension of gamma knife radiosurgery delivery system. This machine has immense promise to treat with short-course regimens with high dose and improve local control without increasing toxicities.