title: Ipsilateral breast tumor relapse: local recurrence versus new primary tumor and the effect of whole-breast radiotherapy on the rate of new primaries.
abstract: OBJECTIVE
  The justification for partial breast radiotherapy after breast conservation surgery assumes that ipsilateral breast tumor relapses (IBTR) outside the index quadrant are mostly new primary (NP) tumors that develop despite radiotherapy. We tested the hypothesis that whole-breast radiotherapy (WBRT) is ineffective in preventing NP by comparing development rates in irradiated and contralateral breasts after tumor excision and WBRT.
  
  
  METHODS
  We retrospectively reviewed 1,410 women with breast cancer who were entered into a prospective randomized trial of radiotherapy fractionation and monitored annually for ipsilateral breast tumor relapses (IBTR) and contralateral breast cancer (CLBC). Cases of IBTR were classified into local recurrence (LR) or NP tumors based on location and histology and were subdivided as definite or likely depending on clinical data. Rates of ipsilateral NP and CLBC were compared over a 15-year period of follow-up.
  
  
  RESULTS
  At a median follow-up of 10.1 years, there were 150 documented cases of IBTR: 118 (79%) cases were definite or likely LR; 27 (18%) cases were definite or likely NP; and 5 (3%) cases could not be classified. There were 71 cases of CLBC. The crude proportion of definite-plus-likely NP was 1.9% (27/1,410) patients compared with 5% (71/1,410) CLBC patients. Cumulative incidence rates at 5, 10, and 15 years were 0.8%, 2.0%, and 3.5%, respectively, for definite-plus-likely NP and 2.4%, 5.8%, and 7.9%, respectively for CLBC, suggesting a difference in the rates of NP and CLBC.
  
  
  CONCLUSIONS
  This analysis suggests that WBRT reduces the rate of ipsilateral NP tumors. The late presentation of NP has implications for the reporting of trials that are testing partial breast radiotherapy.
authors.affiliation: Section of Academic Radiotherapy, Royal Marsden Hospital, Sutton, United Kingdom.
authors.forename: Dorothy M
authors.initials: DM
authors.lastname: Gujral
authors.forename: Georges
authors.initials: G
authors.lastname: Sumo
authors.forename: John R
authors.initials: JR
authors.lastname: Owen
authors.forename: Anita
authors.initials: A
authors.lastname: Ashton
authors.forename: Judith M
authors.initials: JM
authors.lastname: Bliss
authors.forename: Joanne
authors.initials: J
authors.lastname: Haviland
authors.forename: John R
authors.initials: JR
authors.lastname: Yarnold
mesh_terms: D000328:Adult; D000368:Aged; D001940:Breast / Q000473:pathology; D001943:Breast Neoplasms / Q000453:epidemiology / Q000473:pathology / Q000517:prevention & control* / Q000532:radiotherapy* / Q000601:surgery; D003937:Diagnosis, Differential; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015412:Mastectomy, Segmental; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000453:epidemiology / Q000473:pathology / Q000517:prevention & control*; D016609:Neoplasms, Second Primary / Q000453:epidemiology / Q000473:pathology / Q000517:prevention & control*; D009929:Organ Size; D011879:Radiotherapy Dosage; D016032:Randomized Controlled Trials as Topic; D012189:Retrospective Studies; D055815:Young Adult