LETTER TO EDITOR
Year : 2000 | Volume
: 10 | Issue : 3 | Page : 192--193
Better palliation and lesser sequelae by hypofractionated (MRC-Trial) radiotherapy
Pradit Kumar Mohanta, Kamal Verma, Anil Kumar Bahadur
Department of Radiotherapy, Maulana Azad Medical College & Lok Nayak Hospital, New Delhi, India
Pradit Kumar Mohanta
Department of Radiotherapy, Maulana Azad Medical College & Lok Nayak Hospital, New Delhi
|How to cite this article:|
Mohanta PK, Verma K, Bahadur AK. Better palliation and lesser sequelae by hypofractionated (MRC-Trial) radiotherapy.Indian J Radiol Imaging 2000;10:192-193
|How to cite this URL:|
Mohanta PK, Verma K, Bahadur AK. Better palliation and lesser sequelae by hypofractionated (MRC-Trial) radiotherapy. Indian J Radiol Imaging [serial online] 2000 [cited 2020 Jan 20 ];10:192-193
Available from: http://www.ijri.org/text.asp?2000/10/3/192/30605
We have gone through the article by Ranen et al with deep interest . Hypofractionated radiotherapy (MRC Trial) for locally advanced non-small cell lung cancer can be a preferred schedule since it has been shown to be better in terms of cost, compliance and care of the symptoms (palliation) particularly, in the context of our limited infrastructure for cancer treatment. But the authors are silent about the radiobiologic rationale about such a schedule of 17 Gy in two fractions one week apart. However, in advanced stages of cancer when standard treatment is less than satisfactory, such a schedule is sound practice provided adequate care is taken to avoid both early and late sequelae. We wish to suggest two simple modifications in the schedule to keep the radiation accompaniments to a minimum level.
1. Increase the interfraction interval. It is known that prolongation of overall treatment time is one of the most important factors for increasing the differential between effect on the tumor and effect on the vascular connective tissue . Further, by analysis of the volume changes that would be observed before and after irradiation of a hypothetical tumor  a gap two to four weeks can be given before giving the 2 ndsub fraction. This will serve multiple purposes; namely settling of acute radiation morbidity due to previous fraction and allowing the body to clear the dead cells from the tumor, thereby avoiding overkilling. Secondly after the gap (rest), hypoxic cells would come closer to the blood supply and make residual tumor more toxic for the subsequent fraction of radiation. In other words this will be a kind of physiologic sensitization. By further analysis of the curve it is seen that volume changes of the tumor (reduction) reach a nadir at 12 weeks. But accelerated regeneration of surviving cells starts between three and four weeks. So the next fraction can be safely delivered after a gap of two to three weeks and can even be given after a gap of four weeks depending on clinical assessment.
2. Decrease the portal size. Since the aim of the treatment is palliation of symptoms caused by the gross tumor, after giving a gap the tumor shrinks in size. So the portal for the 2 nd fraction should be reduced to encompass only the gross tumor. By doing so significant amount of normal surrounding tissue can be spared. This suggestion is based from the observation that complications decrease with a decrease in the volume of irradiation .
Thus by increasing the inter-fraction interval in the MRC schedule, the overall treatment time is increased without, increasing the total dose. And reducing the portal before the 2 nd fraction, the radiation would be utilized in a more economical fashion and with lesser untoward effect of 8.5 Gy fraction size.
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