Radiosurgery in gastro-intestinal malignancies

Radiosurgery in gastro-intestinal malignancies 

DR.DEBNARAYAN DUTTA, Radaitaion oncologist, Apollo speciality Hospital

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.

Cholangiocarcinoma treated with CyberKnife

Cholangiocarcinoma treated with CyberKnife

Introduction: Cholangiocarcinoma is a relatively rare disease, however has poor prognosis. Liver resection or transplantation is only curative treatment (1). Unfortunately, majority of the patients present with locally advanced, unresectable disease with extensive tumor spread (2). The treatment is not yet standardized. They are treated with either chemotherapy or radiotherapy or in combination (2-6). CyberKnife is recent advancement in radiation therapy delivery system which has high accuracy and flexibility in targeting the tumor through image-guided stereotactic body radiotherapy (SBRT) system (7).

Case history: Forty eight year old gentleman from Uttar Pradesh, India was diagnosed with inoperable cholangiocarcinoma eight months back. He was treated with chemotherapy for four months. However, post-chemotherapy imaging evaluation did not show any significant response. He was diagnosed as chemo-resistant inoperable cholangiocarcinoma. His liver function was maintained and general condition was good. As he was suffering from inoperable, chemotherapy resistant cholangiocarcinoma, he was referred for radiation therapy and was evaluated for robotic radiosurgery (CyberKnife) treatment. After appropriate evaluation, imaging (PET scan), fiducial placement and planning he was treated with CyberKnife. He received 30 Gy in 5 fractions in one week. Dose to the target was adequate and to adjacent normal structures were within normal limits. He completed treatment without any severe toxicity and is on regular follow up.

Discussion: In early operable choloangiocarcinoma, 3-year overall survival rate after curative surgery is only 40-60% (1-2). Advanced unresectable cholangiocarcinoma patients have poorer prognosis as well as severe complications due to biliary stasis (3,4). They are mainly treated with supportive or palliative care. Main aims of treatment in these patients are to preserve quality of life and improve survival rate. Palliative therapy options in these patients are chemotherapy, radiotherapy, photodynamic therapy and biliary drainage procedures (5). Median survival with palliative chemotherapy and external beam radiation therapy are 5 to 9 and 9 to 12 months respectively (2-6). Inoperable, advanced cholangiocarcinomas remain localized and distant metastasis is not common (1). Hence, these tumours may be treated with localized treatment options with maximum effect. However, cholangiocarcinomas are relatively resistant to both radiation and chemotherapy. Hence, high dose radiation therapy is required to have desired loco-regional control (7). CyberKnife radiosurgery is a SBRT using real time respiratory-motion tracking system, and is known to exert minimal normal tissue injury. High dose of radiation treatment in few fractions are possible with CyberKnife which increases tumour control probability without increasing toxicity (7). High dose radiation therapy with proton beam therapy also has shown promising loco-regional control without additional severe toxicity (2). We suggest that CyberKnife might be a safe and useful treatment option in advanced, unresectible cholangiocarcinoma.

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