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.
ABSTRACT
Objective@#To evaluated the unplanned coverage dose to the internal mammary chain (IMC) in patient treated with postmastectomy radiotherapy (PMRT).@*Methods@#One hundred and thirty eight patients with breast cancer receiving radiotherapy (RT) in our hospital were retrospectively analyzed. Patients were divided into three groups: three-dimensional conformal radiotherapy (3D-CRT) group, forward intensity-modulated radiotherapy (F-IMRT) group and inverse IMRT (I-IMRT) group. The IMC were contoured according to Radiation Therapy Oncology Group (RTOG) consensus, and were not include into the planning target volume (PTV). The incidental irradiation dose to IMC among the three groups and the first three intercostal spaces IMC (ICS-IMC 1-3) were all compared, and explored the relationship between the mean doses (Dmean) of IMC and the OARs (ipsilateral lung and heart).@*Results@#The dose delivered to IMC showed no difference in CRT, F-IMRT and I-IMRT(33.80 Gy, 29.65 Gy and 32.95 Gy). And 10.42%, 2.04%, and 9.76% patients achieved ≥45 Gy when treated with CRT, F-IMRT and I-IMRT. For the IMC dose in the first three intercostal spaces (ICS1-3), there was no difference to the three treatment plannings. The Dmean, V20, V30, V40 and V50 of the ICS-IMC2 and ICS-IMC3 were all obviously superior than ICS-IMC1 for all these three plannings. Moderate positive correlation was founded between Dmean for IMC and Dmean for heart for left breast cancer patients underwent CRT (r=0.338, P=0.01). Whereas for F-IMRT and I-IMRT groups, positive correlation were founded between Dmean for IMC and Dmean and V20 for ipsilateral lung for all patients (F-IMRT: r=0.366, P=0.010; r=0.318, P=0.026; I-IMRT: r=0.427, P=0.005; r=0.411, P=0.008).@*Conclusions@#In 3D-CRT, F-IMRT and I-IMRT planning methods, partial patients get IMC irradiated doses that could achieve therapeutic doses. Compared with 3D-CRT, F-IMRT and I-IMRT further reduced the dose of irradiated organs. However, there is no difference in the dose coverage of IMC for the three planned approaches when the IMC made an unplanned target.
ABSTRACT
Objective To explore the dosimetric variance in incidental irradiation to the internal mammary nodes among inverse intensity-modulated radiotherapy (I-IMRT), forward intensity-modulated radiotherapy (F-IMRT),and three-dimensional conformal radiotherapy (3DCRT) after breast-conserving surgery,and to provide a basis for deciding whether to spare the internal mammary nodes in clinical treatment. Methods A total of 84 patients undergoing breast-conserving surgery were enrolled as subjects. The internal mammary nodes in the first three intercostal spaces were contoured. Three radiotherapy plans were designed for each patient. The internal mammary nodes were not included in the planning target volume. Comparison was made among the three plans. The results were compared using Wilcoxon signed rank test. Results The I-IMRT, F-IMRT,and 3DCRT plans had similar median Dmeanvalues for the internal mammary nodes,which were 2 740.2,2973.9,and 2951.4 cGy,respectively. The analyses of the three individual intercostal spaces showed that there was no difference in Dmeanfor the first intercostal space or the second intercostal space between the three plans;For the third intercostal space,however,I-IMRT had a significantly higher Dmeanthan 3DCRT and F-IMRT. The analyses of the three individual plans showed that for each plan,the Dmeanwas the highest in the third intercostal space,followed by the second intercostal space and the first intercostal space. Conclusions All the three plans fail to attain an adequate prescribed dose to cure subclinical disease,and there is no significant difference among the three plans. Therefore,it is risky to exclude the internal mammary nodes using any one of the three radiotherapy techniques for patients with clinical indications for internal mammary nodes radiation. In the combination therapy including chemotherapy,endocrine therapy,and targeted therapy,however,further follow-up is needed to determine whether the incidental irradiation dose to the internal mammary nodes could meet clinical requirement.