163. Field-in-Field versus 3D standard techniques for breast cancer: Dosimetric and reproducibility study

Abstract Purpose Field-in-Field (FIF) is an advanced radiation therapy planning technique [1] . We studied the effectiveness of this technique for breast radiotherapy, with respect to 3D standard technique, in terms of dosimetric benefits and treatment reproducibility. PTV volume dependence on both techniques was also investigated. Methods Two endpoints were analysed. For the first endpoint, dosimetric benefits were studied on 230 breast cancer patients from Macerata hospital who received whole breast radiotherapy with either 3D standard or FIF technique. The second endpoint was a reproducibility study: 28 patients from Macerata and Rieti hospitals were included. For each patient, a 3D standard plan and a FIF plan were prepared on the first simulation CT. All patients underwent other two CT scans on which the original plans were recalculated. Comparisons between techniques were made using V95%, D95%, Dmean, Dmax, HI and CI. Results The FIF technique significantly reduced the PTV Dmax, increased Dmean, allowed better dose coverage and more homogenous dose distribution (Fig. 1). When the irradiated OAR values were compared, the results were slightly higher for the FIF technique, but still within the tolerance limits (p  Differences between plans calculated on the repeated CT scans ( Δ 1/2 and Δ 1/3) were not statistically significant between the two techniques (p  V PTV > 1000 cc ) (Table 1). Conclusions The FIF technique provided better dose distribution in terms of coverage and homogeneity, also for larger PTVs, both techniques respected OAR dose-volume limits and FIF reproducibility was equivalent to 3D standard technique reproducibility. Download high-res image (436KB) Download full-size image