title: Incidental irradiation of internal mammary lymph nodes in breast cancer: conventional two-dimensional radiotherapy versus conformal three-dimensional radiotherapy.
abstract: OBJECTIVE
  To evaluate incidental irradiation of the internal mammary lymph nodes (IMLNs) through opposed tangential fields with conventional two-dimensional (2D) or three-dimensional (3D) radiotherapy techniques and to compare the results between the two techniques.
  
  
  METHODS
  This was a retrospective study of 80 breast cancer patients in whom radiotherapy of the IMLNs was not indicated: 40 underwent 2D radiotherapy with computed tomography for dosimetric control, and 40 underwent 3D radiotherapy. The total prescribed dose was 50.0 Gy or 50.4 Gy (2.0 or 1.8 Gy/day, respectively). We reviewed all plans and defined the IMLNs following the Radiation Therapy Oncology Group recommendations. For the IMLNs, we analyzed the proportion of the volume that received 45 Gy, the proportion of the volume that received 25 Gy, the dose to 95% of the volume, the dose to 50% of the volume, the mean dose, the minimum dose (Dmin), and the maximum dose (Dmax).
  
  
  RESULTS
  Left-sided treatments predominated in the 3D cohort. There were no differences between the 2D and 3D cohorts regarding tumor stage, type of surgery (mastectomy, breast-conserving surgery, or mastectomy with immediate reconstruction), or mean delineated IMLN volume (6.8 vs. 5.9 mL; p = 0.411). Except for the Dmin, all dosimetric parameters presented higher mean values in the 3D cohort (p < 0.05). The median Dmax in the 3D cohort was 50.34 Gy. However, the mean dose to the IMLNs was 7.93 Gy in the 2D cohort, compared with 20.64 Gy in the 3D cohort.
  
  
  CONCLUSIONS
  Neither technique delivered enough doses to the IMLNs to achieve subclinical disease control. However, all of the dosimetric parameters were significantly higher for the 3D technique.
authors.affiliation: MD, Radiation Oncologist, Radiation Oncology Department - Hospital Sírio-Libanês; Radiation Oncology Department - Instituto do Câncer do Estado de São Paulo Octavio Frias de Oliveira (Icesp), São Paulo, SP, Brazil.
authors.forename: Elton Trigo Teixeira
authors.initials: ET
authors.lastname: Leite
authors.affiliation: MD, Radiation Oncologist, Radiation Oncology Department - Hospital Sírio-Libanês, São Paulo, SP, Brazil.
authors.forename: Rafael Tsuneki
authors.initials: RT
authors.lastname: Ugino
authors.affiliation: MD, Radiation Oncologist, Department of Radiology and Oncology - Faculdade de Medicina da Universidade de São Paulo (FMUSP), São Paulo, SP, Brazil.
authors.forename: Marco Antônio
authors.initials: MA
authors.lastname: Santana
authors.affiliation: MD, Radiation Oncologist, Department of Radiology and Oncology - Faculdade de Medicina da Universidade de São Paulo (FMUSP), São Paulo, SP, Brazil.
authors.forename: Denis Vasconcelos
authors.initials: DV
authors.lastname: Ferreira
authors.affiliation: MD, Radiation Oncologist, Radiation Oncology Department - Hospital Sírio-Libanês, São Paulo, SP, Brazil.
authors.forename: Maurício Russo
authors.initials: MR
authors.lastname: Lopes
authors.affiliation: MD, Radiation Oncologist, Radiation Oncology Department - Hospital Sírio-Libanês, São Paulo, SP, Brazil.
authors.forename: Edilson Lopes
authors.initials: EL
authors.lastname: Pelosi
authors.affiliation: MD, Radiation Oncologist, Radiation Oncology Department - Hospital Sírio-Libanês, São Paulo, SP, Brazil.
authors.forename: João Luis Fernandes
authors.initials: JL
authors.lastname: da Silva
authors.affiliation: MD, PhD, Department of Radiology and Oncology - Faculdade de Medicina da Universidade de São Paulo (FMUSP), São Paulo, SP, Brazil.
authors.forename: Heloisa de Andrade
authors.initials: Hde A
authors.lastname: Carvalho
keywords: Breast neoplasms; Lymph nodes/radiation effects; Lymphatic irradiation; Radiotherapy