Purpose/Objective(s): Axilla dissection is not recommended for breast cancer patients with low tumor burden in sentinel lymph nodes if whole breast radiation is planned. The low rate of axillary recurrence was assumed to be attributed to effective systemic therapy and certain amount of axilla coverage by standard whole breast tangential fields (WBTF). This study was to evaluate the coverage of the Level I and II axilla with WBTF, and to what extent that whole axilla radiation could increase the dose to normal tissue.Materials/Methods: Fifteen consecutive left breast cancer patients treated with breast conservative surgery and sentinel node biopsy followed by whole breast radiation were studied. All had inverse IMRT plan using WBTF with prescription dose of 50Gy to 95% of the planning target volume (PTV) of the whole breast. Level I and II axilla was contoured according to the RTOG atlas. The dose distribution and coverage of Level I and II axilla with WBTF was calculated. New plans delivering 50Gy to 95% of the PTV of the whole breast as well as Level I and II axilla (WB+AX) were designed. The homogeneity index (HI=D5/D95) of the whole breast and conformal index (CI=VRI/TV, TV=target volume, VRI=Volume of the Reference Isodose) of the PTV, the dose to the heart, lung, left anterior descending coronary artery (LAD) and contralateral breast were compared between WBTF and WB+AX. Paired T-test was used to compare the differences.Results: The mean volume of Levels I and II axilla was 170.9cm2 (range, 115-254 cm2) and 84.4cm2 (range, 51-131cm2), respectively. With WBTF, the average dose to Levels I and II axilla was 34.39Gy and 21.90Gy, respectively. The V50 and V40 were 22.57 % and 49.86 % for Level I axilla, 5.99% and 21.99% for Level II axilla. Data shown in the table indicated that WB+AX significantly increased the HI of the whole breast and CI of the PTV. WB+AX also significantly increased the dose to the ipsilateral lung and heart as compared with WBTF. There was no significant difference in mean dose to LAD between WBTF and WB+AX.Conclusion: Standard whole breast tangential field doesn’t offer optimal coverage of Level I and II axilla. Patients who had high-risk relapse of axilla should be planned to adequately cover the whole axilla if axilla dissection is not performed. Given the compromised dose homogeneity of the whole breast and the significantly increased lung dose with WB+AX plan, axilla dissection and axilla radiation should be weighted and discussed with patients for those who need axilla treatment.Dosimetric ResultsWBTFWB+AXp ValueBreast HI1.0681.0820.0023PTV CI1.1961.3400.0005Heart V305.48%9.52%0.0000Heart Dmean5.89 Gy6.73 Gy0.0912Lung V2017.10%34.20%0.0000Lung V531.70%51.80%0.0000Lung Dmean9.99 Gy17.32 Gy0.0000LAD Dmean25.75 Gy28.16 Gy0.7538Contralateral Breast Dmean1.28 Gy0.68 Gy0.0407
Peng, R,
Standard Whole Breast Tangential Fields Provide Suboptimal Axillary Coverage and Whole Axilla Radiation Significantly Increase Lung Dose in Chinese Breast Cancer Patients Treated with Breast Conservative Surgery and Sentinel Node Biopsy. Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL.
http://archive.rsna.org/2014/14042663.html
