An analysis of the incidental irradiation to the axillary levels I-III lymph node during radiotherapy after breast conserving surgery

Objective To evaluate the incidental irradiation to the axillary levels Ⅰ, Ⅱ and Ⅲ during the whole breast radiotherapy after breast conserving surgery (BCS) without axillary lymph node dissection (ALND) in breast cancer (BC) patients. Methods A retrospective analysis was performed on the consecutive 42 cases of T1-2N0M0 stage BC patients with sentinel lymphnode biopsy (SLNB) and BCS but without ALND. The axillary lymph nodes of Ⅰ, Ⅱ and Ⅲ were delineated according to RTOG atlas guideline. Three radiotherapy plans including conventional tangential field (CTF), three-dimensional conformal radiotherapy (3D-CRT) and forward-planned intensity-modulated radiotherapy (IMRT) for whole breast irradiation were devised for each case. The Prescription dose was 50 Gy per 25 fractions. Doses to axillary levels (Ⅰ-Ⅲ) were evaluated. Results The mean doses delivered to axillary by the three techniques (CTF, 3D-CRT and IMRT) were (40.1±6.8), (35.4±8.3), (32.9±7.0) Gy for level Ⅰ (F=10.269, P 0.05) and (9.6±6.8), (6.4±4.5), (5.2±3.7) Gy for level Ⅲ (F=8.377, P 0.05), respectively. Conclusions The doses coverage to axillary levels Ⅰ-Ⅲ were all limited in the three techniques. Therefore, it is necessary to assess the risk of axillary lymph node metastasis adequately to develop individualized radiotherapy plans. Key words: Breast neoplasms/radiotherapy; Conventional tangential field; Three-dimensional conformal radiotherapy; Intensity-modulated radiotherapy; Axillary lymph node