title: Incorporating Risk Factors to Identify the Indication of Post-mastectomy Radiotherapy in N1 Breast Cancer Treated with Optimal Systemic Therapy: A Multicenter Analysis in Korea (KROG 14-23).
abstract: OBJECTIVE
  In a recent meta-analysis, post-mastectomy radiotherapy (PMRT) reduced any first recurrence (AFR) and improved survival in N1 and N2 patients. We investigated risk factors for AFR in N1 after optimal systemic therapy without PMRT, to define a subgroup of patients who may benefit from PMRT.
  
  
  METHODS
  One thousand three hundred eighty-two pT1-2N1M0 breast cancer patients treated with mastectomy without PMRT between 2005 and 2010 were retrospectively analyzed. Only 0.6% had no systemic therapy.
  
  
  RESULTS
  After a median follow-up of 5.9 years, there were 173 AFR (53 loco-regional recurrence [LRR] without distant metastases [DM], 38 LRR with DM, and 82 DM without LRR). The 5-year LRR and AFR rates were 6.1% and 12.0%, respectively. Multivariate analysis revealed that close resection margin (p=0.001) was the only independent risk factor for LRR. Multivariate analysis for AFR revealed that age < 35 years (p=0.025), T2 stage (p=0.004), high tumor grade (p=0.032), close resection margin (p=0.035), and triple-negative biological subtype (p=0.031) were independent risk factors. Two or three positive lymph nodes (p=0.078) were considered a marginally significant factor. When stratified by these six factors, the 5-year LRR rates were 3.6% with 0-1 (n=606), 7.5% with 2-3 (n=655), and 12.7% with 4-6 (n=93) risk factors. The 5-year AFR rates were 7.1% with 0-1, 15.0% with 2-3, and 24.5% with 4-6 risk factors.
  
  
  CONCLUSIONS
  Patients with pT1-2N1M0 breast cancer who underwent mastectomy and optimal systemic therapy showed excellent loco-regional control and disease control. The patients with four or more risk factors may benefit from PMRT, and those with two or three risk factors merit consideration of PMRT.
authors.affiliation: Department of Radiation Oncology, Hanyang University Hospital, Seoul, Korea.
authors.forename: Hae Jin
authors.initials: HJ
authors.lastname: Park
authors.affiliation: Department of Radiation Oncology, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Kyung Hwan
authors.initials: KH
authors.lastname: Shin
authors.affiliation: Department of Radiation Oncology, Seoul National University Hospital, Seoul, Korea.
authors.forename: Jin Ho
authors.initials: JH
authors.lastname: Kim
authors.affiliation: Department of Radiation Oncology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Seung Do
authors.initials: SD
authors.lastname: Ahn
authors.affiliation: Department of Radiation Oncology, Asan Medical Center, Seoul, Korea.
authors.forename: Ja Young
authors.initials: JY
authors.lastname: Kim
authors.affiliation: Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Won
authors.initials: W
authors.lastname: Park
authors.affiliation: Department of Radiation Oncology, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Yong Bae
authors.initials: YB
authors.lastname: Kim
authors.affiliation: Department of Radiation Oncology, Proton Therapy Center, National Cancer Center, Goyang, Korea.
authors.forename: Yeon-Joo
authors.initials: YJ
authors.lastname: Kim
authors.affiliation: Department of Radiation Oncology, Dongsan Medical Center, Keimyung University School of Medicine, Daegu, Korea.
authors.forename: Jin Hee
authors.initials: JH
authors.lastname: Kim
authors.affiliation: Department of Radiation Oncology, Ewha Womans University School of Medicine, Seoul, Korea.
authors.forename: Kyubo
authors.initials: K
authors.lastname: Kim
authors.affiliation: Department of Radiation Oncology, Ewha Womans University Mokdong Hospital, Seoul, Korea.
authors.forename: Kyung Ran
authors.initials: KR
authors.lastname: Park
authors.affiliation: Department of Radiation Oncology, CHA Bundang Medical Center, CHA University School of Medicine, Seongnam, Korea.
authors.forename: Hyun Soo
authors.initials: HS
authors.lastname: Shin
authors.affiliation: Department of Radiation Oncology, Gyeongsang National University Hospital, Gyeongsang National University School of Medicine, Jinju, Korea.
authors.forename: Bae Kwon
authors.initials: BK
authors.lastname: Jeong
authors.affiliation: Department of Radiation Oncology, Chonbuk National University Hospital, Jeonju, Korea.
authors.forename: Sun Young
authors.initials: SY
authors.lastname: Lee
authors.affiliation: Department of Radiation Oncology, Seoul Metropolitan Government Seoul National University Boramae Medical Center, Seoul, Korea.
authors.forename: Suzy
authors.initials: S
authors.lastname: Kim
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000235:genetics / Q000401:mortality / Q000473:pathology* / Q000628:therapy*; D003131:Combined Modality Therapy; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008408:Mastectomy; D008875:Middle Aged; D060787:Neoplasm Grading; D009362:Neoplasm Metastasis; D009364:Neoplasm Recurrence, Local; D009367:Neoplasm Staging; D011182:Postoperative Care; D018714:Radiotherapy, Adjuvant; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics; D056910:Republic of Korea; D012307:Risk Factors; D055815:Young Adult
chemical_list: D018719:Erb-b2 Receptor Tyrosine Kinases
keywords: Breast neoplasms; Post-mastectomy radiotherapy; Risk factors