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KMID : 1164220120240020095
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Journal of Korean Society for Radiotherapeutic Technology
2012 Volume.24 No. 2 p.95 ~ p.106
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Assessment of the Usefulness of an IMRT Plan Using a Shell-Type Pseudo Target with Patients in Stage III or IV of NSCLC
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Lee Sang-Bong
Park Ki-Ju
Park Du-Chan
Kim Man-Wo
Kim Jun-Gon
Noh Sung-Hwan
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Abstract
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Purpose: The objective of this study was to investigate the usefulness of an IMRT treatment plan according to whether there was a shell-type pseudo target during radiation therapy for patients in Stage III or IV of non-small cell lung cancer (NSCLC).
Materials and Methods: After setting an IMRT (Intensity-Modulated Radiation Therapy, IMRT) plan for when there was a shell-type pseudo target (SPT) and when there was none (WSPT) with 22 patients in Stage III or IV of NSCLC, the investigator analyzed dose-volume histograms (DVHs) and made assessment with dosimetric comparisons such as homogeneity index (HI) inside the tumor target, conformity index (CI) of the tumor target, spinal cord maximum dose, Esophagus V50%, mean lung dose (MLD), and V40%, V30%, V20%, V10%, V5%.
esults: The mean CI of WSPT and SPT was 1.22±0.04 and 1.16±0.032 (.000*), respectively, and the mean HI of WSPT and SPT was 1.06±0.015 and 1.07±0.014 (.000*), respectively. In SPT, the mean of each CI difference decreased by －5.16±2.54%, while HI increased by average 0.81±0.47%. Esophagus V50% recorded 14.54±12.01% (WSPT) and 12.14±11.09% (.000*, SPT) with the mean of SPT differences dropping by －26.37±25.05%. Mean spinal cord maximum dose was 3,898.44±1,075.0 cGy (WSPT) and 3,810.8±1,134.9 cGy (.004*, SPT) with SPT dropping by average －3.36±5.81%. As for lung VX%, the mean of V5% and V10% differences was －1.62±2.29% (.006*) and －1.98±5.02% (.005*), respectively with SPT making a decrease. The mean of V20%, V30%, and V40% differences was －3.51±3.07% (.000*), －4.84±6.01% (.000*), and －6.16±8.46% (.001*), respectively, with SPT making a decrease with statistical significance. In MLD assessment, SPT also dropped by average －2.83± 2.41% (.000*). Those results show that SPT allows for mean 169 cGy (Max: 547 cGy, Min: 6.4 cGy) prescription dose.
Conclusion: An IMRT treatment plan with SPT during radiation therapy for patients in Stage III or IV of NSCLC will help to reduce the risk of lung toxicity and radiation-induced pneumonia by cutting down radiation doses entering the normal lung, reduce the local control failure rate during radiation therapy due to increasing prescription doses to a certain degree, and increase treatment effects.
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KEYWORD
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IMRT (intensity-modulated radiation therapy), DVH (dose volume histogram), NSCLC (non-small cell lung cancer)
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