Field-in-field plan does not improve the dosimetric outcome compared with the wedged beams plan for breast cancer radiotherapy

To evaluate and compare the dosimetry of field-in-field (FIF) and wedged beams (WB) techniques for patients with breast cancer receiving adjuvant radiotherapy after conservative surgery. A total of 89 patients with breast cancer participated in this study. Each patient received a computed tomography–based treatment plan with opposed tangential fields. Two planning techniques (FIF and WB) were generated for each patient by using the Pinnacle treatment-planning system. Three indices, the homogeneity index (HI), conformity index (CI), and uniformity index (UI), as well as maximum dose (D_max), median dose (D₅₀), number of portals, monitor unit (MU), and lung volume at 20 Gy (lung₂₀) were used for comparison. The mean values tested using a t-test indicated that the WB technique had a significantly lower HI (p < 0.0001), a significantly higher CI (p < 0.0001), and a significantly higher D₅₀ (p = 0.0002) than did the FIF technique. The FIF technique had a significantly higher D_max compared with the WB technique, but lung₂₀ did not exhibit a significant difference. By contrast, the FIF technique had a significantly higher UI and a significantly lower MU compared with the WB technique, but a significantly higher number of portals were found in the FIF technique. The FIF technique did not demonstrate superior dosimetric results. The WB technique had a significantly lower HI, higher CI, lower D_max, and lower number of portals; but the FIF technique had a significantly higher UI and lower MU.