Abstract
We retrospectively generated IMRT plans for 14 NSCLC patients who had experienced grade 2 or 3 esophagitis (CTCAE version 3.0). We generated 11‐beam and reduced esophagus dose plan types to compare changes in the volume and length of esophagus receiving doses of 50, 55, 60, 65, and 70 Gy. Changes in planning target volume (PTV) dose coverage were also compared. If necessary, plans were renormalized to restore 95% PTV coverage. The critical organ doses examined were mean lung dose, mean heart dose, and volume of spinal cord receiving 50 Gy. The effect of interfractional motion was determined by applying a three‐dimensional rigid shift to the dose grid. For the esophagus plan, the mean reduction in esophagus V50, V55, V60, V65, and V70 Gy was 2.8, 4.1, 5.9, 7.3, and 9.5 cm3, respectively, compared with the clinical plan. The mean reductions in LE50, LE55, LE60, LE65, and LE70 Gy were 2.0, 3.0, 3.8, 4.0, and 4.6 cm, respectively. The mean heart and lung dose decreased 3.0 Gy and 2.4 Gy, respectively. The mean decreases in 90% and 95% PTV coverage were 1.7 Gy and 2.8 Gy, respectively. The normalized plans’ mean reduction of esophagus V50, V55, V60, V65, and V70 Gy were 1.6, 2.0, 2.9, 3.9, and 5.5 cm3, respectively, compared with the clinical plans. The normalized plans’ mean reductions in LE50, LE55, LE60, LE65, and LE70 Gy were 4.9, 5.2, 5.4, 4.9, and 4.8 cm, respectively. The mean reduction in maximum esophagus dose with simulated interfractional motion was 3.0 Gy and 1.4 Gy for the clinical plan type and the esophagus plan type, respectively. In many cases, the esophagus dose can be greatly reduced while maintaining critical structure dose constraints. PTV coverage can be restored by increasing beam output, while still obtaining a dose reduction to the esophagus and maintaining dose constraints.PACS number: 87.53 Tf
Highlights
164 Niedzielski et al.: Esophagus-sparing treatment plans long-term survival.[4]
The concept of partial sparing of the esophagus has been studied previously.[7,8,9] Even though a definitive relationship between volume or length of the esophagus receiving greater than a certain dose and sparing the esophagus has not been established, it is reasonable to surmise that length of esophagus receiving greater than a certain threshold dose induces esophagitis.[7,8,9] reduced esophageal dose plans may represent esophagus-sparing treatment plans
14 patients with NSCLC previously treated at MD Anderson Cancer Center were selected that presented with grade 2 or 3 acute esophagitis based on the Common Terminology Criteria for Adverse Events (CTCAE) version 3.0.(20) These patients potentially benefit the most, in terms of early effects, from dose reduction to the esophagus
Summary
164 Niedzielski et al.: Esophagus-sparing treatment plans long-term survival.[4]. CCT can significantly increase tumors’ response to radiation and patients’ median survival duration, but may increase the severity of early effects in normal tissue.[5]. Previous studies have shown dosimetric variables that describe spatial distribution of dose, such as volume of esophagus receiving at least 20 Gy (V20) or length of esophagus receiving full circumference dose of at least 60 Gy (LE60), significantly predict high-grade esophagitis.[12,15,16,17] Wei et al[3] found significance between V10–V45 and high-grade radiation esophagitis (RE), and V20 and CCT as significant in multivariate analysis. Other studies have shown V50 and V60 have a better correlation to patient outcome other studies using DVH metrics.[15] Since there is no single, definitive dosimetric value from these metrics that predicts RE, it is important to consider a variety of values. The concept of partial sparing of the esophagus has been studied previously.[7,8,9] Even though a definitive relationship between volume or length of the esophagus receiving greater than a certain dose and sparing the esophagus has not been established, it is reasonable to surmise that length of esophagus receiving greater than a certain threshold dose induces esophagitis.[7,8,9] reduced esophageal dose plans may represent esophagus-sparing treatment plans
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