CyberKnife Radiosurgery in lung cancer

Stereotactic radiosurgery in lung cancer DR.DEBNARAYAN DUTTA, Consultant Radiation Oncologist, Apollo speciality hospital Chennai

Radiosurgery is a non-invasive option in early lung cancer. High dose precise radiosurgery has immense potential. Early data from phase II studies have shown excellent loco-regional control and survival function. CyberKnife Radiosurgery in lung cancer has following advantages: 1.     Cyberknife has the unique technology of ‘see and shoot’. In this technology before each treatment field matching of the target and ‘intra-fraction motion correction’ is done, hence minimal normal lung comes in the radiation field. 2.      Cyberknife has sub-millimeter treatment accuracy. Margin (planning target volume) required (where normal lung comes) is minimal around the target. High dose region volume is minimal with Cyberknife and lung toxicity is expected to be lower compared with conventional treatment. 3.     Cyberknife has the multiple isocentric technique with non-coplanar field arrangement, hence have unmatched conformity index (uniform dose is delivered). Cyberknife use ‘pencil beam’ with multiple small beamlets delivered from various angles (maximum 1200 different position) hence ‘penumbra’ margin is less. 4.     As dosimetry is favorable and total dose delivered with Cyberknife is not higher compared with conventional fraction (usual dose delivered with Cyberknife 60 Gy/3 fr/ 1 week) there is no expected increase in lung toxicity with Cyberknife. Phase II prospective studies with Cyberknife have not shown any increase in radiation induced pneumonitis. 5.     ‘STAR trial’ is a multicentric randomized study initiated by MD Anderson Cancer Centre may provide answer to impact of Cyberknife on lung toxicity. There are other few ongoing clinical studies with hypofractionated radiation therapy on lung cancer that will provide useful information in near future   For more information of successful treatments using cyberknife you may please blog your comments or write to lakshmipriya_b@apollohospitals.com Radiosurgery in brain tumours Short course radiation therapy is the 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 it’s 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 short course of treatment regimen with higher dose per fraction without increasing in toxicity. In brain tumours, radiosurgery with gamma-knife is considered standard of care in many of the clinical indications such as small meningiomas, acaustic 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 to 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 invasive frame, 3) has inverse planning system, can spare critical structure, 4) there is a ‘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-millimeter accuracy and unmatched dose distribution.  The advanced technology behind CyberKnife uses image guidance technology and computer-controlled robotics to deliver and 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 gammaknife radiosurgery delivery system. This machine has immense promise to treat with short course regimens with high dose and improve local control without increasing toxicities.