Coverage of Axillary Lymph Nodes with Tangential Breast Irradiation in Korea: A Multi-Institutional Comparison Study

Introduction. To evaluate the dose distribution and coverage of axilla using only tangential field for whole breast radiotherapy (RT) at three institutions in Korea. Methods. We used computed tomography (CT) images of nine consecutive 1-2 sentinel lymph node-positive patients who underwent breast conserving surgery and whole breast RT without axillary lymph node (ALN) dissection for clinical T1-2N0 breast cancer. The CT data were transferred to three radiation oncologists in 3 institutions and each radiation oncologist created treatment plans for all nine patients; a total of 27 treatment plans were analyzed. Results. The mean doses delivered to levels I and II were 31.9 Gy (9.9-47.9 Gy) and 22.3 Gy (3.4-47.7 Gy). Ninety-five percent of levels I and II received a mean dose of 11.8 Gy (0.4-43.0 Gy) and 3.0 Gy (0.3-40.0 Gy). The percent volumes of levels I and II covered by 95% of the prescribed dose were only 29.0% (0.2-74.1%) and 11.5% (0.0-70.1%). The dose distribution and coverage of axilla were significantly different between three institutions (p = 0.001). Conclusion. There were discrepancies in ALN coverage between three institutions. A standardization of whole breast RT technique through further research with a nationwide scale is needed.