Comparison between the four-field box and field-in-field techniques for conformal radiotherapy of the esophagus using dose–volume histograms and normal tissue complication probabilities

Abstract

Purpose

We evaluated and compared the performance of the field-in-field (FIF) to that of the four-field box (4FB) technique regarding dosimetric and radiobiological parameters for radiotherapy of esophageal carcinoma.

Materials and methods

Twenty patients with esophageal cancer were selected. For each patient, two treatment plans were created: 4FB and FIF. The parameters compared included the conformity index (CI), homogeneity index (HI), D _mean, D _max, tumor control probability (TCP), V _20Gy and V _30Gy of the heart and lungs, normal tissue complication probability (NTCP), and monitor units per fraction (MU/fr).

Results

A paired t-test analysis did not show any significant differences (p > 0.05) between the two techniques in terms of the CI and TCP. However, the HI significantly improved when the FIF was applied. D _max of the PTV, lung, and spinal cord were also significantly better with the FIF. Moreover, the lung V _20Gy as well as the NTCPs of the lung and spinal cord significantly reduced when the FIF was used, and the MU/fr was significantly decreased.

Conclusions

The FIF showed evident advantages over 4FB: a more homogeneous dose distribution, lower D _max values, and fewer required MUs, while it also retained PTV dose conformality. FIF should be considered as a simple technique to use clinically in cases with esophageal malignancies, especially in clinics with no IMRT.

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