Dose reduction to normal tissues as compared to the gross tumor by using intensity modulated radiotherapy in thoracic malignancies

The purpose of this paper is to evaluate the impact of IMRT in reducing the dose to the critical normal tissues while maintaining the desired dose to the volume of interest for thoracic malignancies.During the period January 2002 to March 2004, 12 patients of various sites of malignancies in the thoracic region were treated using physical intensity modulator based IMRT. Plans of these patients treated with IMRT were analyzed using dose volume histograms.An average dose reduction of the mean values by 73% to the heart, 69% to the right lung and 74% to the left lung, with respect to the GTV could be achieved with IMRT.The 2 year disease free survival was 59% and 2 year overall survival was 59%. The average number of IMRT fields used was 6.IMRT with inverse planning enabled us to achieve desired dose distribution, due to its ability to provide sharp dose gradients at the junction of tumor and the adjacent critical organs.Curative doses of radiation in many instances may lead to a good disease control but cause radiation induced chronic morbidities such as interstitial capillary injury of the myocardium leading to an increased incidence of coronary artery disease, cardiomyopathy and pulmonary interstitial fibrosis. These toxicities are dose related and different structures have varying tolerance to radiation. The availability of data on tissue tolerances makes it imperative to respect the tolerance of critical structures such as the heart, lungs, esophagus etc. and reduce associated morbidities while improving the quality of life.In most clinical situations, the radiation oncologist is compromised in prescription to treat to tolerance doses of normal tissues rather than to specific tumoricidal dose. IMRT has the potential to increase this therapeutic ratio. The use of IMRT as against conventional radiation allows one to sculpt the dose around a complex shaped target, and has the potential to deliver a higher biologically effective dose to the target. A number of studies