Irradiation of the chest wall and regional nodes as an integrated volume with IMRT for breast cancer after mastectomy: from dosimetry to clinical side-effects / 中华放射肿瘤学杂志

ABSTRACT

ObjectiveTo discuss dosimetric characteristics of an intensity-modulated radiotherapy (IMRT) technique for treating the chest wall and regional nodes as an integrated volume after modified radical mastectomy ( MRM ),and observe acute side-effects following irradiation.Methods From June 2009 to August 2010,75 patients were randomly enrolled.Of these,41 had left-sided breast cancer.Each eligible patient had a planning CT in treatment position,on which the chest wall,supraclavicular,and infraclavicular nodes,+/-internal mammary region,were contoured as an integrated volume.A muhi-beam IMRT plan was designed with the target either as a whole or two segments divided at below the clavicle head.A dose of 50 Gy in 25 fractions was prescribed to cover at least 90％ of the PTV.Internal mammary region was included in 31 cases.Dose volume histograms were used to evaluate the IMRT plans.The acute side effects were followed up regularly during and after irradiation.The independent two-sample t-test was used to compare the dosimetric parameters between integrated and segmented plans.ResultsPlanning design was completed for all patients,including 55 integrated and 20 segmented plans,with median number of beams of 8.The conformity index and homogeneity index was 1.43 ± 0.15 and 0.14 ± 0.02,respectively.Patients with internal mammary region included in PTV had higher homogeneity index PT.The percent volume of PTV receiving ＞ 110％ prescription dose was ＜ 5％.None of the dose constraints to normal structures was violated.There were statistically significant differences in the means of dosimetric parameters of PTV,such as Dmax,DmeanV107％,and V110％,between integrated and segmented plans (t=2.19 -2.53,P=0.013-0.031 ).≥ grade 2 radiation dermatitis was identified in 3 2 patients ( grade 2 in 2 2 patients,grade 3 in 10 patients ),mostly occurred within 1 - 2 weeks after treatment.The sites of moist desquamation were anterior axillary fold (27/37) and chest wall (10/37).Only 2 patients developed grade 2 radiation pneumonitis.Conclusions The IMRT technique applied after MRM with integrated locoregional target volume is dosimetrically feasible,and the treatment was proved to be well-tolerated by most patients.