Guidelines for Complications of Cancer Treatment Vol VIII Part B

Prevention of Pneumonitis and Lung fibrosisIdeally, pulmonary toxicity should be prevented. Whileadministering radiotherapy, the normal lung volumes and dosesshould be minimized and given in accordance to acceptedtolerance. In case of any concomitant drug therapy monitoringof symptoms/signs, pulmonary function tests, and chest x-rayscan aid detecting problems early and the causative agent canbe withdrawn.The omission of Elective nodal irradiation (ENI) considerablyreduces V20. It has been seen that the shape of the planningtarget volume (PTV) in the transverse plane (expressed as anelliptical index) affects the conformity of the V20 isodose tothe PTV..Fluorodeoxyglucose-positron emission tomography(FDGPET)/ CT is a functional nuclear medicine study thathas been shown to be more accurate than CT in determiningthe extent of NSCLC. Preliminary studies have shown thatco-registered PET/CT alters GTV delineation in about 50%of NSCLC patients compared with targeting using CT alone.PET is especially useful in differentiating disease fromatelectasis, something often difficult to discern in aconventional CT scan. This in turn leads to reduction in targetvolumes and consequent sparing of more normal lung.Four dimensional (4D) imaging is becoming increasinglyutilized for treatment planning in radiotherapy (RT). Generally,4DCT information is used to (1) determine the tumor marginto account for the extent of tumor motion on patient specificbasis or to (2) choose a gating phase and window forrespiratory-gated RT (gated-RT) treatment planning. 4D-CTderived patient-specific margins have been shown to lead to areduction of the tumor margin in RT plan, which in turnsignificantly reduces the ipsilateral lung toxicity. Gated-RTplans lead to significant reductions of V20, V40, and Normaltissue complication probability (NTCP). (J Antony, abstract)319