title: Does the intent to irradiate the internal mammary nodes impact survival in women with breast cancer? A population-based analysis in British Columbia.
abstract: OBJECTIVE
  To determine the value of the intent to include internal mammary nodes (IMNs) in the radiation therapy (RT) volume for patients receiving adjuvant locoregional (breast or chest wall plus axillary and supraclavicular fossa) RT for breast cancer.
  
  
  METHODS
  2413 women with node-positive or T3/4N0 invasive breast cancer, treated with locoregional RT from 2001 to 2006, were identified in a prospectively maintained, population-based database. Intent to include IMNs in RT volume was determined through review of patient charts and RT plans. Distant relapse free survival (D-RFS), breast cancer-specific survival (BCSS), and overall survival (OS) were compared between the two groups. Prespecified pN1 subgroup analyses were performed.
  
  
  RESULTS
  The median follow-up time was 6.2 years. Forty-one percent of study participants received IMN RT. The 5-year D-RFS for IMN inclusion and exclusion groups were 82% vs. 82% (p = 0.82), BCSS was 87% vs. 87% (p = 0.81), and OS was 85% vs. 83% (p = 0.06). In the pN1 subgroup, D-RFS was 90% vs. 88% (p = 0.31), BCSS was 94% vs. 92% (p = 0.18), and OS was 91% vs. 88% (p = 0.01). After potential confounding variables were controlled for, women who received IMN RT did not have significantly different D-RFS (hazard ratio [HR] = 1.02 (95% confidence interval [CI], 0.84-1.24; p = 0.85), BCSS (HR = 0.98 (95% CI, 0.79-1.22; p = 0.88), or OS (HR = 0.95; 95% CI, 0.78-1.15; p = 0.57). In the pN1 subgroup, IMN RT was associated with trends for improved survival that were not statistically significant: D-RFS (HR = 0.87; 95% CI, 0.63-1.22; p = 0.42), BCSS (HR = 0.85; 95% CI, 0.57-1.25; p = 0.39), and OS (HR = 0.78; 95% CI, 0.56-1.09; p = 0.14).
  
  
  CONCLUSIONS
  After a median follow-up time of 6.2 years, although intentional IMN RT was not associated with a significant improvement in survival, this population-based study suggests that IMN RT may contribute to improved outcomes in selected patients with N1 disease.
authors.affiliation: BC Cancer Agency, Radiation Therapy Program, BC, Canada. rolson2@bccancer.bc.ca
authors.forename: Robert A
authors.initials: RA
authors.lastname: Olson
authors.forename: Ryan
authors.initials: R
authors.lastname: Woods
authors.forename: Caroline
authors.initials: C
authors.lastname: Speers
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Lau
authors.forename: Andrea
authors.initials: A
authors.lastname: Lo
authors.forename: Pauline T
authors.initials: PT
authors.lastname: Truong
authors.forename: Scott
authors.initials: S
authors.lastname: Tyldesley
authors.forename: Ivo A
authors.initials: IA
authors.lastname: Olivotto
authors.forename: Lorna
authors.initials: L
authors.lastname: Weir
mesh_terms: D001943:Breast Neoplasms / Q000401:mortality* / Q000473:pathology / Q000532:radiotherapy*; D001955:British Columbia; D018572:Disease-Free Survival; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015182:Lymphatic Irradiation / Q000379:methods / Q000401:mortality*; D008207:Lymphatic Metastasis; D015412:Mastectomy, Segmental; D008875:Middle Aged; D018714:Radiotherapy, Adjuvant / Q000379:methods / Q000401:mortality