Different radiation techniques to deliver therapeutic dose to the axilla in patients with sentinel lymph node-positive breast cancer: Doses, techniques challenges and clinical considerations.

PURPOSE: To evaluate the coverage of different levels of axillary lymph nodes and organs at risk according to the field design of AMAROS study (levels I-II-III-IV), breast tangents with supraclavicular and infraclavicular fields (levels II-III-IV) and high tangent fields to the breast after breast-conserving surgery.

MATERIALS AND METHODS: We delineated the axillary lymph nodes levels I-IV in 34 patients treated with breast-conserving surgery and sentinel lymph nodes biopsy. Field design according to AMAROS study - levels I-IV in patients without axillary dissection - as well as irradiation of levels II-IV used in N+ patients after axillary dissection, and also high tangent fields was simulated. Mean dose levels and volumes covered by 95% or 80% isodoses were evaluated. Doses to ipsilateral lung, heart and brachial plexus were compared. Paired t test was used.

RESULTS: AMAROS study and levels II-IV plans delivered therapeutic dose to high axilla (levels II-IV), but the high tangent fields showed inefficacy to cover these volumes, P<0.001). In terms of organs at risk, especially, ipsilateral lung, AMAROS study plan was found to significantly increase the volume receiving at least 10Gy (I-IV:46.8%, II-IV: 39%), but also the volume receiving at least 20Gy (I-IV: 39.3%, II-IV: 31.3%), and V30Gy (I-IV: 34.2% vs II-IV: 26.1%), as well as the mean dose (I-IV: 18.6Gy, II-IV: 15.2Gy, P<0.001).

CONCLUSIONS: The omission of axillary dissection and the axilla irradiation need is associated with high dose irradiation of the lungs, and with higher toxicity. The indication of axillary dissection or irradiation of low axilla could be individualized in relation with individual comorbidities and factors of risk.