Field-in-field technique for upper abdominal malignancies in clinical radiotherapy.

Background: In upper abdominal malignancies (UAM), due to the presence of multiple inhomogeneous tissues, a wedge-based conformal treatment planning results in high-dose regions inside the target volume. Aim: This study was designed to explore the feasibility of using a field-in-field (FIF) technique in different UAM and its efficacy in reducing the high-dose regions. Materials and Methods: Twelve patients of UAM (which included malignancies of the gastroesophageal junction, stomach, gall bladder, and pancreas) were selected for this study. Computed tomography (CT) scans were performed and three-dimensional conformal wedge plans were generated for all the cases. The same plan was copied with the wedges removed and a FIF plan was generated. The two plans were compared for mean, maximum, and median doses; dose received by 2% (D2) and 98% (D98) of the target volume; volume receiving >107% (V > 107%) and <95% (V < 95%) of the prescribed dose; conformality index (CI); and total monitor units. The doses to critical structures such as liver, kidneys, and spinal cord were also compared. Statistical Analysis: Statistical analysis was performed with SPSS, version 10.0. Results: For all the cases, the FIF technique was better than wedge-based planning in terms of maximum dose, D2, V > 107%, and CI; there was a statistically significant reduction in monitor units. With regard to doses to critical structures, there was marginal dose reduction for the kidneys and spinal cord with FIF as compared to wedge-based planning. Conclusion: The FIF technique can be employed for UAM in place of wedge-based conformal treatment plans. [ABSTRACT FROM AUTHOR]