Influencing factors of dose coverage of unplanned irradiation of internal mammary lymph node drainage area in patients receiving radiotherapy after mastectomy / 中华放射肿瘤学杂志

ABSTRACT

Objective@#To investigate the influencing factors of the dose coverage of unplanned internal mammary lymph node (IMN) irradiation in patients receiving chemotherapy after mastectomy.@*Methods@#Clinical data of 138 patients receiving radiotherapy in the upper and lower lymph node drainage area of the thoracic wall and clavicle [three-dimensional conformal radiotherapy (3DCRT), field-in-field forward intensity-modulated radiotherapy (F-IMRT) or inverse IMRT (I-IMRT)] were retrospectively analyzed. The IMN was delineated according to the Radiation Therapy Oncology Group (RTOG) criteria. The unplanned irradiation dose of the IMN was obtained. The correlation between the IMN irradiation dose, clinical characteristics and specific parameters of radiotherapy during the unplanned irradiation was statistically analysed.@*Results@#The mean dose of unplanned IMN irradiation was 32.85 Gy (range: 2.76-50.93 Gy). In total, 7.3% of breast cancer patients obtained the therapeutic dose of≥ 45 Gy. Body weight, body mass index (BMI), body surface area (BSA) and thoracic transverse diameter (DT) were lower, whereas the planning target volume of IMN (VIMN) included in the chest wall PTV (IMNin) and the ratio of IMNin to VIMN were higher compared with those of their counterparts with insufficient therapeutic dose. Multivariate regression analysis demonstrated that body weight, thoracic anteroposterior diameter (DAP), DT, RIMNin and PTV volume were the influencing factors of the dose coverage of unplanned IMN irradiation (P=0.000, 0.000, 0.001, 0.000 and 0.034).@*Conclusions@#For patients receiving chemotherapy after mastectomy, the dose coverage significantly varies when the IMN is the unplanned target. Partial patients achieve the therapeutic dose. The dose coverage of unplanned IMN irradiation is influenced by physical characteristics, anatomical features and technical parameters of radiotherapy, which should be emphasized during the study design and result analysis.