title: Postmastectomy internal mammary nodal irradiation: a long-term outcome.
abstract: OBJECTIVE
  The internal mammary lymph nodes (IMN) have been recognized as a potential site of regional breast cancer spread. The aim of this study was to evaluate the impact of internal mammary node radiotherapy (RT) to on clinical outcomes in breast cancer patients treated with mastectomy and postoperative radiation therapy.
  
  
  METHODS
  This cohort study included 588 patients with breast cancers located in the central and medial quadrants. IMN RT was applied to 320 patients and 268 patients did not receive it IMN RT. Inside the IMN RT group, 165 patients received external beam IMN irradiation (IMN-EB). Mastectomy combined with using Californium-252 neutron source implantation was applied to 155 patients (IMN-BT). Cox proportional hazards modeling was used to determine the influence of IMN RT on clinical outcome. Age, tumor size, lymph nodal status, adjuvant radiotherapy, chemotherapy and hormonal therapy were assessed.
  
  
  RESULTS
  IMN-EB resulted in a significant improvement of distant metastasis-free survival, breast cancer-specific survival and overall survival (P=0.033, P=0.037 and P=0.011, respectively). The IMN-EB radiotherapy has a significant impact on event-free survival (HR, 0.67; 95% CI, 0.46-0.91; P=0.043) and breast cancer-specific survival (HR, 0.64; 95% CI, 45-0.91; P=0.013) in patients with moderate-risk (stage T1-2N1). There was no association between IMN RT and clinical outcomes of patients with high-risk disease (stage T3-4N2-3) in any of the study end points.
  
  
  CONCLUSIONS
  The effects of IMN-EB radiotherapy on event-free survival and breast cancer-specific survival were benefit for women with moderate-risk breast cancer.
authors.affiliation: Radiotherapy and Drug Therapy Centre, National Cancer Institute, Vilnius, Lithuania.
authors.forename: Eduardas
authors.initials: E
authors.lastname: Aleknavičius
authors.affiliation: Scientific Research Centre, National Cancer Institute, Vilnius, Lithuania.
authors.forename: Vydmantas
authors.initials: V
authors.lastname: Atkočius
authors.affiliation: Cancer Control and Prevention Center, National Cancer Institute, Vilnius, Lithuania.
authors.forename: Irena
authors.initials: I
authors.lastname: Kuzmickienė
authors.affiliation: Radiotherapy and Drug Therapy Centre, National Cancer Institute, Vilnius, Lithuania. Electronic address: rita.steponaviciene@vuoi.lt.
authors.forename: Rita
authors.initials: R
authors.lastname: Steponavičienė
mesh_terms: D000328:Adult; D001943:Breast Neoplasms / Q000401:mortality* / Q000532:radiotherapy* / Q000601:surgery; D002142:Californium / Q000627:therapeutic use; D015331:Cohort Studies; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D008198:Lymph Nodes / Q000528:radiation effects*; D008408:Mastectomy; D008875:Middle Aged; D011184:Postoperative Period; D018714:Radiotherapy, Adjuvant; D016896:Treatment Outcome
chemical_list: D002142:Californium
keywords: Breast cancer; Internal mammary lymph nodes; Radiotherapy