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.

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.