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 (Dmax), median dose (D50), number of portals, monitor unit (MU), and lung volume at 20Gy (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 Dmax 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 Dmax, and lower number of portals; but the FIF technique had a significantly higher UI and lower MU.