Gastrointestinal Malignancies - How Radiosurgery Can Help?

Common gastro-intestinal (GI) malignancies are colon cancer, carcinoma rectum and anal canal, pancreatic cancer, cholangiocarcinoma, carcinoma stomach, hepatocellular carcinoma (HCC) and liver metastasis. Other uncommon tumours include gastro-intestinal stromal tumour (GIST), klaskin tumour and neuro-endocrine tumour. Surgery is the treatment option in these tumours. Unfortunately, majority of these tumours are inoperable at presentation and treated with supportive/palliative intent. Majority of these tumours are relatively chemotherapy (CT) resistant. Role of conventional radiation therapy (RT) in gastro-intestinal malignancies are also not well defined in many of these tumours.

• Response rate with delivered dose is not acceptable, and dose escalation is not possible with conventional RT without compromising in critical structure (small intestine, duodenum) tolerance. With modern stereotactic whole body RT (SBRT) higher dose of radiation can be delivered in shorter duration and normal tissue tolerance is respected. SBRT has evolved in recent years and also have promise to improve local control in these relative resistant tumours. Pre-operative and adjuvant RT is established in carcinoma of rectum.
• In recent years, short course RT (hypofractionated RT, 25 Gy/5 Fr) had shown to be equally effective as conventional RT (1.8-2 Gy/Fr) in inoperable rectal cancer. Role of conventional RT in inoperable pancreatic cancer has been argued in the EORTC study. Whereas, short course RT (fractionated radiosurgery) is slowly being accepted as an option to complete RT early, start adjuvant CT at the earliest and also improve quality of life (QOL). In liver metastasis, radiosurgery is a non-invasive alternative to surgery. Higher equivalent radiation dose delivered with radiosurgery there may have comparable survival function in selected patients.
• Radiosurgery is an option in liver tumour close to porta, sub-diaphragmatic location (segment VIII), nodal involvement and in medically inoperable patients. In hepatocellular carcinoma (HCC), fractionated radiosurgery is an option as ‘bridge therapy’ for patients waiting for liver transplant, medically inoperable patients, chemotherapy resistant, post TACE residual and in recurrent HCCs. Radiosurgery is also consider as primary treatment in suitable patients. There is an ongoing multicentric randomized trial comparing chemotherapy and radiosurgery in HCCs.
• In uncommon slow growing tumours such as cholangiocarcinoma, neuro-endocrine tumour and klaskin tumour fractionated radiosurgery have excellent response rate and improve symptoms. In conclusion, modern fractionated stereotactic radiosurgery is an option in many of the GI malignancies improves response rate and also may improve QOL. In coming years with publication of more matured data from randomized and prospective phase II studies the role of radiosurgery will be established. ours , 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.

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