Deep-inspiration breath-hold radiation therapy in breast cancer: A word of caution on the dose to the axillary lymph node levels.

Purpose: To assess the differences in unintended regional nodal irradiation between free breathing (FB) and deep-inspiration breath-hold (DIBH) during tangential field irradiation. Methods and Materials: We randomly chose 32 patients from our database who underwent both DIBH and FB treatment planning. Contouring of the axillary lymph node levels (LI, LII, and LIII) was performed retrospectively according to the Radiation Therapy Oncology Group contouring atlas. We assessed the center of mass of each level and the planning target volume, as well as the dose distribution (Dmean, Dmedian, Dmax, Dmin, V30, and V40) in the lymph node levels I-III. Subsequently center of mass movement and dose changes due to deep inspiration treatment planning were calculated. Results: All lymph node levels showed significant (P<.001) movement in anterior and cranial directions due to DIBH. The overall median movement (range) in the x (lateral), y (anterior-posterior), and z (cranio-caudal) directions was 0.1 cm (0.0-1.1 cm), 0.9 cm (0.1-2.0 cm), and 1.2 cm (0.0-2.6 cm), respectively. Movement of the planning target volume showed significant correlation (r=0.72, r=0.63, r=0.63; P<.05) with levels I-III. The average Dmean during FB/DIBH was as follows: LI 33.9 Gy/30.8 Gy (P<.001), LII 23.7 Gy/24.1 Gy (P=.74), and LIII 14.0 Gy/15.6 Gy (P=.14). V30 was as follows: LI 63.8%/56.5% (P<.001), LII 44.6%/45.5% (P=.76), and LIII 24.2%/27.8% (P<.05). V40 was as follows: LI 58.9%/51.0% (P<.001), LII 39.3%/40.1% (P=.79), and LIII 20.4%/23.9% (P<.05). Conclusions: Deep-inspiration breath-hold results in a significant dose reduction in level I. Only minor changes in dose distribution were recorded for levels II and III. Thus, DIBH seems to have an impact on unintended regional nodal irradiation as compared with FB