RESUMO
Objective:To explore whether internal mammary node irradiation (IMNI) can control the normal tissue volume dose within a reasonable range under inverse-planned intensity-modulated radiation therapy (IP-IMRT).Methods:The patients with breast cancer received postmastectomy combined with radiotherapy from January 2015 to July 2016 in Department of Radiation Oncology in Ruijin Hospital Affiliated to Shanghai Jiaotong University School of Medicine were retrospectively screened and sampled. The prescription dose was 50 Gy/25 times. The whole heart and ipsilateral lung were outlined on CT scan, and the dose-volume histogram parameters were quantified in the RT planning system (ADAC Pinnacle).Results:For the left breast cancer patients ( n=67) who received IMNI, the total heart dose-volume histogram parameters in 2016 were significantly decreased compared with those in 2015. The D mean in 2015 was (976.65±411.16) cGy, significantly larger than (687.47±134.65) cGy in 2016( P=0.008). Among the same sampled population, the percentage of whole heart D mean at the doses of 12 Gy, 10 Gy, 8 Gy was 33.3%, 33.3%, and 66.7% in 2015, and 0%, 3.8%, and 11.5% in 2016, respectively. For the right breast cancer patients ( n=65) , D mean, V 2Gy, V 10Gy, V 15Gy and V 20Gy of the heart in the IMNI group were significantly higher than those in the non-IMNI group in 2016(all P<0.05). For the ipsilateral lung, D mean, V 10Gy, V 20Gy, and V 30Gy in the IMNI group were remarkably higher than those in the non-IMNI group (all P<0.05). Conclusions:IMNⅡs found to be associated with increased cardiopulmonary dose volume with IP-IMRT technique. Nevertheless, with the practical experience of IMRT and the increasing awareness of cardiac dose limitation, it is feasible to control the cardiac dose increment within a limited range.