High Tangent Radiation Therapy With Field-in-Field Technique for Breast Cancer

PURPOSE: We evaluated whether the field-in-field (FIF) technique improves the homogeneity of the target in high tangent radiation therapy (HTRT). MATERIALS AND METHODS: This study included 30 patients. In total, 3 HTRT plans were created: 1 with conventional opposed fields (Conv-p), 1 with the FIF technique (FIF-p), and 1 with FIF technique using lung-blocked subfields (FIF-LB-p). RESULTS: The maximum dose of the breast and planning target volume (PTV) was significantly lower for FIF-p and FIF-LB-p than Conv-p. Homogeneity index of PTV was also significantly lower for FIF-p and FIF-LB-p than Conv-p. Homogeneity index of the breast or PTV was significantly better for FIF-p than FIF-LB-p. The volumes of the breast or the PTV receiving 95% and 90% of the prescribed dose were also significantly better for FIF-p, indicating the advantages of FIF-p. CONCLUSIONS: The FIF technique was useful in HTRT and improved homogeneity in the target.