title: The effect of age in breast conserving therapy: a retrospective analysis on pathology and clinical outcome data.
abstract: OBJECTIVE
  Age is an important prognostic marker of patient outcome after breast conserving therapy; however, it is not clear how age affects the outcome. This study aimed to explore the relationship between age with the cell quantity and the radiosensitivity of microscopic disease (MSD) in relation to treatment outcome.
  
  
  METHODS
  We employed a treatment simulation framework which contains mathematic models for describing the load and spread of MSD based on a retrospective cohort of breast pathology specimens, a surgery simulation model for estimating the remaining MSD quantity and a tumor control probability model for predicting the risk of local recurrence following radiotherapy.
  
  
  RESULTS
  The average MSD cell quantities around the primary tumor in younger (age⩽50years) and older patients were estimated at 1.9∗10(8)cells and 8.4∗10(7)cells, respectively (P<0.01). Following surgical simulation, these numbers decreased to 2.0∗10(7)cells and 1.3∗10(7)cells (P<0.01). Younger patients had smaller average surgical resection volume (118.9cm(3)) than older patients (162.9cm(3), P<0.01) but larger estimated radiosensitivity of MSD cells (0.111Gy(-1) versus 0.071Gy(-1), P<0.01).
  
  
  CONCLUSIONS
  The higher local recurrence rate in younger patients could be explained by larger clonogenic microscopic disease cell quantity, even though the microscopic disease cells were found to be more radiosensitive.
authors: Department of Radiation Oncology, Netherlands Cancer Institute, Amsterdam, The Netherlands.
authors: Wei
authors: W
authors: Chen
authors: Department of Radiation Oncology, Netherlands Cancer Institute, Amsterdam, The Netherlands.
authors: Jan-Jakob
authors: JJ
authors: Sonke
authors: Department of Radiation Oncology, Fundação Champalimaud, Lisboa, Portugal.
authors: Joep
authors: J
authors: Stroom
authors: Department of Radiation Oncology, Netherlands Cancer Institute, Amsterdam, The Netherlands.
authors: Harry
authors: H
authors: Bartelink
authors: Department of Radiation Oncology, Netherlands Cancer Institute, Amsterdam, The Netherlands.
authors: Marcel
authors: M
authors: Verheij
authors: Department of Radiology, University Medical Centre Utrecht, The Netherlands. Electronic address: K.G.A.Gilhuijs@umcutrecht.nl.
authors: Kenneth
authors: K
authors: Gilhuijs
mesh_terms: D000367:Age Factors; D001943:Breast Neoplasms / Q000473:pathology* / Q000532:radiotherapy / Q000601:surgery / Q000628:therapy*; D003131:Combined Modality Therapy; D005260:Female; D006801:Humans; D015412:Mastectomy, Segmental; D008875:Middle Aged; D009010:Monte Carlo Method; D009364:Neoplasm Recurrence, Local / Q000473:pathology; D011836:Radiation Tolerance / Q000502:physiology; D012189:Retrospective Studies; D016896:Treatment Outcome
keywords: Age; Breast conserving therapy; Microscopic disease quantity; Monte–Carlo simulation; Radiosensitivity; Tumor control probability