Esophageal cancer dose escalation using a simultaneous integrated boost technique

Abstract

Purpose: We previously showed that 75% of radiation therapy (RT) failures in patients with unresectable esophageal cancer are in the gross tumor volume (GTV). We performed a planning study to evaluate if a simultaneous integrated boost (SIB) technique could selectively deliver a boost dose of radiation to the GTV in patients with esophageal cancer.

Methods and materials: Treatment plans were generated using four different approaches (two-dimensional conformal radiotherapy [2D-CRT] to 50.4 Gy, 2D-CRT to 64.8 Gy, intensity-modulated RT [IMRT] to 50.4 Gy, and SIB-IMRT to 64.8 Gy) and optimized for 10 patients with distal esophageal cancer. All plans were constructed to deliver the target dose in 28 fractions using heterogeneity corrections. Isodose distributions were evaluated for target coverage and normal tissue exposure.

Results: The 50.4 Gy IMRT plan was associated with significant reductions in mean cardiac, pulmonary, and hepatic doses relative to the 50.4 Gy 2D-CRT plan. The 64.8 Gy SIB-IMRT plan produced a 28% increase in GTV dose and comparable normal tissue doses as the 50.4 Gy IMRT plan; compared with the 50.4 Gy 2D-CRT plan, the 64.8 Gy SIB-IMRT produced significant dose reductions to all critical structures (heart, lung, liver, and spinal cord).

Conclusions: The use of SIB-IMRT allowed us to selectively increase the dose to the GTV, the area at highest risk of failure, while simultaneously reducing the dose to the normal heart, lung, and liver. Clinical implications warrant systematic evaluation.

Conflict of interest statement

Conflicts of Interest Notification: The authors declare no conflicts of interest.

Copyright © 2012 Elsevier Inc. All rights reserved.

Figures

Fig. 1

(top row) Axial, sagittal, and coronal views of a 2D-CRT plan to deliver 50.4 Gy to a patient with esophageal cancer, similar to the plans used in Intergroup 0123. (bottom row) A modern plan for delivering 50.4 Gy as intensity-modulated radiation therapy to the same patient with esophageal cancer.

Figure 2

(top row) Axial, sagittal, and coronal views of an intensity-modulated radiation therapy (IMRT) plan with the planning target volume being treated to 50.4 Gy. (bottom row) Simultaneous integrated boost IMRT plan with the gross tumor volume being treated to 64.8 Gy and the planning target volume to 50.4 Gy.

Figure 3

(top row) Axial, sagittal, and coronal view of a 2D-CRT plan to deliver 50.4 Gy to a patient with esophageal cancer (similar to the plans used in Intergroup 0123). (bottom row) Simultaneous integrated boost IMRT plan with the gross tumor volume being treated to 64.8 Gy and the planning target volume to 50.4 Gy.

Figure 4

Dose volume histogram of an individual patient comparing an a 2D-CRT plan (dashed line) to 50.4 Gy (similar to that used in Intergroup 0123) to a simultaneous integrated boost (SIB)-IMRT plan (solid line) in which the gross tumor volume is treated to 64.8 Gy and the planning target volume to 50.4 Gy. The SIB-IMRT plan increased the mean GTV dose by 28% (p = 0.001) and decreased the mean heart dose by 30% (p = 0.001), the mean total lung dose by 23% (p = 0.007), and the lung V20 by 37% (p = 0.004).