Augest.29 : During a radiation treatment session and also from one treatment session to another, tumours can move due to normal internal organ action (digestion, elimination, and breathing). This unplanned position/ movement of tumour leads it to not receiving the full amount of radiation it should and normal tissues may receive more radiation than they can tolerate.
Through this treatment, the tumour-bearing area, mapped by a radiation oncologist, is imaged and a reconstruction of the anatomy by virtual CT-scan is carried out in the treatment machine. The images are acquired using diagnostic X-rays (Kilovoltage imaging) also known as Cone Beam CT-scanning: the advantage of this is a lesser dose of X-rays radiation being received by the patient.
Image Guided Radiotherapy or IGRT is best suited for sites where internal organ motion is expected. For example, cancer of lung, breast and liver (breathing motion), stomach and prostate (filling), brain (neck movement). The use of image guidance not only improves the focus and precise delivery of radiation, it is expected to improve upon the cure rates for cancers where the dose delivery is limited with conventional methods of radiotherapy due to proximity of affected tissues to critical organs like eyes, brain, heart, lungs and spinal cord.
Today, IGRT has become a harbinger of hope for millions of cancer patients for the many benefits it offers. Not only has this technique significantly improved survival rates amongst cancer patients, it has also resulted in reducing the side-effects of radiation like difficulty in swallowing food and pneumonia for patients with cancers in the chest. Another advantage is that as the cancer shrinks with treatment, it will be possible for physicians to implement adaptive radiotherapy using IGRT. Adaptive radiotherapy is a new concept in radiotherapy where individual patient data is collected for the first few fractions of treatment and is then used to individualise treatment for the remaining fractions and treatment is re-planned based upon the tumour shrinkage.
As compared to conventional radiotherapy, by increasing the daily dose of radiation with image guidance, smaller normal tissue coverage can be given, thus reducing the overall treatment time. This increases the compliance for treatment completion and reduces the number of visits to the hospital, resulting in greater patient comfort.
At present, there are three such facilities in India offering image guided therapy, All India Institute of Medical Sciences, New Delhi, Artemis Health Institute, Gurgaon and Indo American Hospital in Hyderabad.
The writer is head, radiation oncology, at Artemis Health Institute, Gurgaon
Dr Tejinder Katariya