Publication date: February 01, 2011
Category: Lung cancer and other chest malignancies
Authors: P. Pedicini; R. Caivano; G. Califano; V. Barbieri; P. Sanpaolo; A. Fiorentino; G. Castaldo; V. Fusco
Purpose/Objective: To increase the biological effectiveness of IMRT in Non Small Cell Lung Cancer (NSCLC). Materials and Methods: a total of 29 patients affected by nonresectable NSCLC in stage III-a/b were planned by SIB-IMRT together with a strategy of limited treated volume. The IMRT plans were shared in a first-phase (P1), more toxic for spinal-cord and less toxic for joined-lungs, and in a second-phase (P2), more toxic for joined-lungs and less toxic for spinal-cord, on both therapeutic and prophylactic volumes. Afterward many fractionation schemes were tested using a biological dose volume histogram (BE-DVH). The BEDVH is obtained transforming the standard DVH from new index called “Toxicity Index”, defined for each OAR by linear quadratic model with condition of equal radiobiological effect on the target volume. BE-DVH allows a prior analysis and the assessment of choice of fractionation biologically most effective in terms of reduced toxicity for the organs at risk (OAR). Results: The best fractionation was a hyper-fractionation in P1 followed by a hypo-fractionation in P2. The overall treatment gives 4.0% of sparing for spinal-cord without significant changes forjoined-lungs toxicity (p < 0.001). The same method, applied in the case of accelerated fractionation with two fractions per day, gives 9.7% of sparing for spinal-cord, 4.8% of sparing for V20 on joined-lungs and significant sparing also for the other OARs (p < 0.001). Conclusion: The BE-DVH allows us to choose in advance the best dose fractionation in NSCLC significantly reducing the toxicity for all the OARs.