The department of Radiation Oncology at Amrita Institute of Medical Sciences, Kochi recently conducted Amrita Annual High Precision Radiation Therapy Workshop and CME over the course of three days on 30th June, 1st and 2nd July 2017. The workshop focused on imparting hands on training on the use of CyberKnife. The academic session included a live demonstration on the treatment of liver tumors. Liver tumors are very common in Kerala and it is difficult to treat using traditional methods in certain cases. However, radiosurgery serves as a treatment option for these patients. Additionally, the experts taking these sessions represented top hospitals across the country including Tata Memorial Hospital, Fortis Hospital and Apollo Hospital just to name a few.
CyberKnife is an option in Inoperable and Recurrent Liver Cancer: Dr Debnarayan Dutta
Hepatocellular carcinoma is a cancer of the liver cells. It is usually associated hepatitis infections, toxins (hepato-toxins), many chemicals we use daily, alcohol and also with substance abuse. As per the ICMR data, incidence of hepatocellular carcinoma ranges from 0.7 to 7.5 per 100,000 in the Indian population. Liver cancer is a problem in Kerala; there is an assumption that the incidence is higher than the national average.
Majority of these primary liver cancers (hepatocellular carcinoma) are treated with surgery, trans-arterial chemo embolization (TACE) and radiofrequency ablation (RFA). But, as majority the of these patients are presented with advanced disease since recurrence is common. Many patients have blockade in the portal vein (portal vein thrombosis), and they have only few treatment options available. These patients are usually on palliative chemotherapy with dismal prognosis. Many of these patients have preserved functional status (good general condition), and there is a dilemma regarding their management. There is a need to explore newer treatment options in these 'difficult to treat' patients. Sometimes, surgery is also difficult in patients with small lesions close to porta hepatis (blood vessels) and subdiaphramatic (below the diaphragm - subdiaphramatic location) location. These patients usually don't have any suitable treatment option and are treated with chemotherapy.
Primary liver cancer is relatively chemotherapy and radio-resistant. Higher doses of radiation or specific chemotherapy are required to have any significant clinical benefit. There is a technical challenge in delivering high dose to the liver tumour and sparing other parts of normal liver. Hence, radiation therapy was never considered as a viable option in liver tumours, till recently. We have recently found a technique to deliver high dose of radiation to the tumour safely. The liver is sensitive to radiation therapy, and tolerance is low. It means that even a low dose of radiation on the whole liver will cause 'radiation induced liver injury'. Normal radiation therapy with high 'scattering' of dose leads to high 'mean' dose to liver. Therefore, it is difficult to deliver high dose with standard radiation equipment. Liver moves with respiration, hence we need to treat a larger area with standard radiation equipment, and hence higher dose to liver is delivered.
Primary liver tumour (Hepatocellular carcinoma, cholangiocarcinoma) need a higher dose of radiation needs to be delivered, which not possible with standard radiation machines. With available radiation machines deliver higher dose to normal liver and less than appropriate dose to the tumour. A high dose to liver is associated with toxicity and lower dose to tumour with response to treatment. Hence, with standard radiation therapy techniques there are higher side effects and lower response to treatment. Radiation therapy was never considered an option previously as an option even in inoperable or recurrent disease. There are only few systemic therapy options in hepatocellular carcinoma (Sorafinib) and the outcome is par below the expectations.
Radiosurgery is a precise radiation therapy delivery technique to deliver high dose radiation to the target while sparing the adjacent critical structures. Robotic radiosurgery (CyberKnife) is a robot assisted 'real time' image guided radiation therapy delivery technique where high dose short course radiation therapy is delivered to the target sparing adjacent normal liver.
High-resolution contrast CT scan and MRI scan helps to locate the tumour accurately, computer assisted contouring and planning system helps to plan the treatment precisely. CyberKnife treatment does not need any margin, as there is real time tracking and the robot 'chase' the tumour during respiratory motion. Gold seeds called 'fiducials' are placed near the tumour and the machine has the capability to track the 'fiducials' during real time imaging and treatment. Hence, high dose radiation therapy is delivered precisely with robotic arm based linear accelerator to the moving target with real time tracking and real time imaging. Accuracy of treatment is very high (within 1 mm) and monitored by computer-assisted systems.
Higher dose to the target and sparing of normal liver has enabled physicians to deliver high dose radiation to the target, which has translated to better local control with lesser side-effects. Usually, 45 Gy of radiation dose is delivered to the target in three days as out-patient procedure. As a policy, 800 cc of normal liver is saved to function properly. Usual liver volume is around 1200 to 1500 cc. There is no major toxicities during treatment and a large proportion of patients respond to treatment at 2 to 3 months follow up evaluation.
CyberKnife robotic radiosurgery is considered the most appropriate treatment option for fiducial guided liver cancer treatment. CyberKnife is an option in otherwise inoperable situations, such as tumour close to porta or subdiaphramatic location or multiple lesions in different lobes of liver. Radiosurgery with CyberKnife is now considered a standard option in inoperable, recurrent/ progressive liver tumours. There are many prospective randomized trials being conducted world over to find if CyberKnife can be an option even in smaller lesions as a non-invasive option even in operable liver cancers. Early studies with smaller lesion have shown that CyberKnife is equally effective as surgery with lesser side effects.
There is a need to increase awareness regarding the liver cancer treatment options, especially in inoperable or 'difficult to do surgery' patients those are relatively young (less than 60 years) and have preserved function status (good general condition).