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 compare the dosimetric difference in forward intensity modulation radiotherapy (fIMRT)and inverse IMRT(iIMRT)planning for breast cancer.Methods Six patients received radiotherapy alone after left breast-conserving surgery were selected.For each patient,two treatment phns(flMRT and iIMRT)were designed with Pinnacle3 7.4f.In each plan,the volume of PIT received prescription dose was not less than 95 %.The dosimetrie parameters were assessed with dose volume histograms in planning target volume (PIT)and organ of around risk(OAR).Results Of flMRT and ilMRT plans,the PTV average canformal indexwere(0.67±0.06)and(0.66±0.06)(t = 2.423,P ＞ 0.05),average homogeneity index were (28.2±6.0)% and(26.1±6.8)%(t = 2.164,P ＞ 0.05);the volume of left lung received 20 Gy(V20)were(18.7±3.3)% and(17.0±2.8)%(t =5.087,P<0.05),and V30 of left lung were(15.5±3.0)%and(14.0±2.6)%(t =7.272,P<0.05);V30 of heart were(4.1±3.1)% and(3.5±2.5)%(t=1.916,P ＞ 0.05);the total monitor units were(262±5)MU and(308±14)MU(t = 7.515,P < 0.05).Conclusions There were no significant differences of CI,HI,and V30 of heart between flMRT and iIMRT.Because of fewer MUs,fIMRT plan could reduce the machine abrasion and treatment time,but V30 and V30 of left lung are higher significantly than iIMRT plan.