Assessment of Dose Delivery to Supraclavicular and Axillary Lymph Nodes in Adjuvant Breast Cancer Radiotherapy, with or without Posterior Axillary Boost in Relation to BMI

Background: The axillary and supraclavicular nodal volume treatment resultsin improvement of local control and survival after breast conserving surgery (BCS)or modified radical mastectomy (MRM). Studies on the depth of these nodes havequestioned the consistent use of standard fields for all patients. This study wasdone to assess the dose delivery to these lymph nodes with conventional treatmenttechniques according to body mass index (BMI).Methods: Twenty six patients with breast cancer undergoing breast surgerywere included and computed tomography (CT) simulation was done. Theiraxillary and supraclavicular nodal volumes were contoured for planning targetvolume (PTV). Supraclavicular and posterior axillary fields were generated foreach patient with digital reconstruction radiography (DRR) technique. Then thedose distribution of the two conventional methods - anterior-posterior field (AP),and anterior field with posterior boost (AP+PAboost) - for total dose of ۵۰۰۰ cGy,was examined with radiotherapy dose plan program.AnAP planned field suitablefor PTV, was designed and compared to AP+PAboost. The diameter of axilla wasmeasured at the center ofAPfield inCTscan. Data were analyzed in relationship toBMI.Results: PTV coverage and excessively irradiating normal tissues (hot points),proved to have significant differences in each method (p < ۰.۰۰۱ to ۰.۰۱). Axillaryand supraclavicular LNs were in ۱.۶ to ۱۰ and ۰.۵ to ۶.۳ cm depth, respectively.Depth of the prescribed dose, which was gained from planned field, had asignificant statistical association withBMI(p < ۰.۰۵).Conclusions: Current standard fields are not appropriate for all patients,because of poor coverage of PTV. To sum up, ۳D CT planning is stronglyrecommended for patients with high BMI.

Keywords:

Dosimetry , breast cancer , posterior boost , axillary lymph nodes , supraclavicular lymph nodes