title: The Value of Ki67 in Very Young Women with Hormone Receptor-Positive Breast Cancer: Retrospective Analysis of 9,321 Korean Women.
abstract: BACKGROUND
  Young breast cancer patients have a poorer prognosis, especially when their tumors are hormone receptor positive. We analyzed the association between Ki67 and age and the impact of these factors on outcomes in hormone receptor-positive breast cancer.
  
  
  METHODS
  The records of 9,321 hormone receptor-positive invasive breast cancer patients from three large centers were retrospectively reviewed. Each institution separately assayed Ki67 level immunohistochemically. Univariate and multivariate analysis for recurrence-free survival (RFS) was performed on 4,738 patients from a single center.
  
  
  RESULTS
  Ki67 level was inversely proportional to age in all three data sets and was significantly higher for younger patients (p < 0.001, 0.03, and <0.001, respectively). This correlation was seen only in the human epidermal growth factor receptor 2 (HER2)-negative population. Survival analysis showed that both very young age (<35 years) and high Ki67 level (≥10 %) were independent prognostic factors. Although young age was a worse prognostic indicator regardless of HER2 status, Ki67 index was associated with worse prognosis only in HER2-negative patients. When patients were stratified into those with low and high Ki67, young age remained a significant factor for RFS, with hazard ratios in these two Ki67 groups of 2.15 and 2.57, respectively (p < 0.001). Also, the young age/low Ki67 group had significantly poorer RFS than the older age/high Ki67 group (p < 0.001).
  
  
  CONCLUSIONS
  Ki67 level was higher in younger patients. However, very young patients had a poorer prognosis regardless of Ki67 level. Unknown biologic factors other than high cell proliferation might play a role in the aggressiveness of hormone receptor-positive breast cancer in very young patients.
authors: Department of Surgery, Asan Medical Center, Ulsan University College of Medicine, Seoul, Korea.
authors: Jisun
authors: J
authors: Kim
authors: Department of Surgery, Seoul National University College of Medicine, Seoul, Korea. hanw@snu.ac.kr.
authors: Wonshik
authors: W
authors: Han
authors: Center for Breast Cancer, Research Institute and Hospital, National Cancer Center, Gyeonggi-do, Korea.
authors: So-Youn
authors: SY
authors: Jung
authors: Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors: Yeon Hee
authors: YH
authors: Park
authors: Department of Surgery, Seoul National University College of Medicine, Seoul, Korea.
authors: Hyeong-Gon
authors: HG
authors: Moon
authors: Momm's Clinic, Seoul, Korea.
authors: Soo Kyung
authors: SK
authors: Ahn
authors: Department of Surgery, Iwha University College of Medicine, Seoul, Korea.
authors: Jun Woo
authors: JW
authors: Lee
authors: Department of Surgery, Seoul National University College of Medicine, Seoul, Korea.
authors: Min Kyoon
authors: MK
authors: Kim
authors: Department of Surgery, Seoul National University College of Medicine, Seoul, Korea.
authors: Jong Jin
authors: JJ
authors: Kim
authors: Department of Surgery, Seoul National University College of Medicine, Seoul, Korea.
authors: Eun Shin
authors: ES
authors: Lee
authors: Department of Surgery, Asan Medical Center, Ulsan University College of Medicine, Seoul, Korea.
authors: Tae Kyung
authors: TK
authors: You
authors: Center for Breast Cancer, Research Institute and Hospital, National Cancer Center, Gyeonggi-do, Korea.
authors: Han-Sung
authors: HS
authors: Kang
authors: Center for Breast Cancer, Research Institute and Hospital, National Cancer Center, Gyeonggi-do, Korea.
authors: Eun Sook
authors: ES
authors: Lee
authors: Center for Breast Cancer, Research Institute and Hospital, National Cancer Center, Gyeonggi-do, Korea.
authors: Jungsil
authors: J
authors: Ro
authors: Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors: Jeong Eon
authors: JE
authors: Lee
authors: Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors: Seok Jin
authors: SJ
authors: Nam
authors: Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors: Young-Hyuck
authors: YH
authors: Yim
authors: Department of Surgery, Seoul National University College of Medicine, Seoul, Korea.
authors: In Ae
authors: IA
authors: Park
authors: Department of Surgery, Seoul National University College of Medicine, Seoul, Korea.
authors: Dong-Young
authors: DY
authors: Noh
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000737:chemistry* / Q000473:pathology / Q000628:therapy; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D019394:Ki-67 Antigen / Q000032:analysis*; D008207:Lymphatic Metastasis; D008875:Middle Aged; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000032:analysis*; D011960:Receptors, Estrogen / Q000032:analysis; D011980:Receptors, Progesterone / Q000032:analysis; D056910:Republic of Korea; D012189:Retrospective Studies; D012307:Risk Factors; D055815:Young Adult
chemical_list: D019394:Ki-67 Antigen; D018719:Erb-b2 Receptor Tyrosine Kinases; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; C508053:ERBB2 protein, human