title: Unplanned irradiation of internal mammary lymph nodes in breast cancer.
abstract: OBJECTIVE
  To evaluate the incidental dose to the internal mammary chain (IMC) in patients treated with three-dimensional conformal radiotherapy, to estimate the predictors affecting the magnitude of IMC receiving dose and to determine the predictive role of clinical parameters on survival.
  
  
  METHODS
  Between 2009 and 2015, 348 patients undergoing RT for breast cancer were retrospectively analyzed. All patients underwent our department's routine procedure for breast cancer. The internal mammary lymph nodes were contoured according to Radiation Therapy Oncology Group (RTOG) concensus. Based on each patient's dose-volume histograms, the mean doses (Dmean) to internal mammary gland were analyzed. Overall survival and disease-free survival were also evaluated.
  
  
  RESULTS
  The median follow-up time was 38 (range 3-80) months. The Dmeanto IMC was 32.8 Gy and the dose delivered to IMC showed a greater coverage in modified radical mastectomy (MRM) group compared with breast conserving surgery (34.6 vs 26.7 Gy). The T-stage of tumor and the N-stage of tumor affected the incidental dose to IMC. The tumor size, the number of involved lymph nodes, the percentage of involved lymph nodes, hormonal status, advanced T-stage and advanced N-stage were the prognostic factors that affect survival.
  
  
  CONCLUSIONS
  The IMC received meaningful incidental irradiation dose when treated with two opposite tangential fields and ipsilateral supraclavicular fossa with a single anterior field. The real effect of incidental dose on survival and the hypothesis about the benefit of incidental irradiation of IMC should be examined in clinical studies.
authors.affiliation: Department of Radiation Oncology, Necmettin Erbakan University Meram Medicine School, Akyokus Mevkii, 42090, Konya, Turkey. drgulgun@yahoo.com.
authors.forename: Gul
authors.initials: G
authors.lastname: Kanyilmaz
authors.affiliation: Department of Radiation Oncology, Necmettin Erbakan University Meram Medicine School, Akyokus Mevkii, 42090, Konya, Turkey.
authors.forename: Meryem
authors.initials: M
authors.lastname: Aktan
authors.affiliation: Department of Radiation Oncology, Necmettin Erbakan University Meram Medicine School, Akyokus Mevkii, 42090, Konya, Turkey.
authors.forename: Mehmet
authors.initials: M
authors.lastname: Koc
authors.affiliation: Department of Radiation Oncology, Necmettin Erbakan University Meram Medicine School, Akyokus Mevkii, 42090, Konya, Turkey.
authors.forename: Hikmettin
authors.initials: H
authors.lastname: Demir
authors.affiliation: Department of Public Health and Biostatistics, Necmettin Erbakan University Meram Medicine School, Konya, Turkey.
authors.forename: Lütfi Saltuk
authors.initials: LS
authors.lastname: Demir
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001940:Breast; D001943:Breast Neoplasms / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D008198:Lymph Nodes / Q000528:radiation effects*; D008875:Middle Aged; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal; D012189:Retrospective Studies; D016019:Survival Analysis
keywords: Breast cancer; Dose-volume analysis; Internal mammary chain; Radiotherapy; Survival analysis