A comparison between Cyber knife and Rapid Arc in prostate cancer radiotherapy

A comparison between Cyber knife and Rapid Arc in prostate cancer radiotherapy
Aida Karami,^1,* Marziyeh Tahmasbi,²
1. Department of Radiologic Technology, Faculty of Paramedicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
2. Department of Radiology Technology, School of Allied Medical Sciences, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
Introduction: Prostate cancer (PCa) is the second most common cancer among men all over the world. North America has the highest occurrence rate of PCa. However, Iran has the less occurrence of PCa includes 7-9% of all cancers. Various techniques of radiotherapy (RT) are established for PCa treatment such as intensity modulated radiation therapy (IMRT) and stereotactic body radiation therapy (SBRT). The aim of this review was to present a comparison between two novel treatment techniques: Cyber knife and Rapid Arc in prostate cancer radiotherapy.
Methods: The present review article was performed by searching “Pubmed” and “google scholar” by different combinations of terms “radiotherapy” and “prostate cancer” and “VMAT” and “cyberknife” and “rapidarc”. 40 articles were obtained. After removing the reiterative and reviewing abstracts, 22 articles were selected and reviewed full text.
Results: IMRT is the standard and most frequently used radiation modality in PCa which delivers photons in various dose distribution while reducing the surrounding normal tissue toxicity compared with conventional radiotherapy. Volumetric modulated arc therapy (VMAT) is a developmental type of IMRT with 360 degrees gantry rotation around the patient, provides high conformal dose distribution, also minimize radiation dose to organs at risk (OARs) around the tumor. A new common form of VMAT is called Rapid Arc (RA) developed to achieve precisely more radiation dose to cancerous cell during sparing healthy tissues with different dose rate and speed variations of the gantry revolution. It can be considered ideal for PCa radiotherapy. Advantages of utilizing Rapid Arc modality are high target volume coverage; faster delivery and minimum treatment time as the name reveals ( lasts less than 2 minutes, approximately 2-8 times more rapid than prior techniques) due to the continuous gantry rotation, so prevent cancerous cell DNA repair; meliorating target volume conformity exclusively in targets with intricate shapes; more accurate target delivery due to time shortening which results in decreasing patient movement and target position (e.g. 4-11 minutes delivery time in lung cancer RT), improves patient comfort. But even with low dose radiation there is still the detrimental radiobiological risks; the therapeutic radiation techniques are costly as well. The clinical usage of Rapid Arc is constantly expanding. Cyberknife (CK) is a novel radiosurgery robotic device used to deliver high dose hypo-fractionated SBRT. Its first usage for PCa was done in 2003. It has been utilized to treat tumors of the pancreas, lung, spine, kidney, liver, prostate, head and neck. Although, cyber knife couldn`t be successful in metastatic recurrent PCa treatment, the benefits of this modality are high precision; late toxicity (Rare rectal toxicity and bleeding). However, testicular toxicity may be still exists in cyber knife, but this method has better accuracy (less than 5 mm) than other external radiotherapy modalities; Patient positioning and tumor adjustment without stopping treatment during delivery due to motion robotic system is another benefit of this method. It might be expensive though.
Conclusion: Studies reveal that compared to cyber knife, Rapid Arc modality is more available and attain improved critical tissue sparing, better target dose distribution, highest dose conformity, and lower dose areas of bladder and rectum. More Scattered radiation and longest treatment and beam-on time with cyber knife (34 minutes) compared to the shortest with Rapid Arc (5.1 minutes) are obtained. Also, higher mean dose to prostate and planning target volume in cyber knife treatment method is seen. In conclusion, to decrease treatment and delivery time, RA achieves better outcomes although there`s still no apparent dosimetric priority between RA and CK, so more experimental studies are needed.
Keywords: Radiotherapy, Rapid Arc, Cyber knife, Prostate cancer