title: Efficacy of Letrozole as First-Line Treatment of Postmenopausal Women with Hormone Receptor-Positive Metastatic Breast Cancer in Korea.
abstract: OBJECTIVE
  Letrozole showed efficacy and generally favorable toxicities, along with the convenience of oral administration in postmenopausal patients with hormone receptor (HR)-positive metastatic breast cancer (MBC). To the best of our knowledge, there have been no reports of the clinical outcomes in Korean patients, although letrozole is widely used in practice. Therefore, this studywas conducted to affirm the efficacy and toxicities of letrozole in Korean patients.
  
  
  METHODS
  This study retrospectively analyzed 84 HR-positive MBC patients who had been treated with letrozole from January 2001 to December 2012. Clinicopathological characteristics and treatment history were extracted from medicalrecords. All patients received 2.5 mg letrozole once a day until there were disease progressions or unacceptable toxicity. Progression-free survival (PFS) was the primary endpoint, and secondary endpoints were overall survival (OS), objective response rate (ORR), and toxicity.
  
  
  RESULTS
  The median age of the subjects was 59.3 years. Letrozole treatment resulted in a median PFS of 16.8 months (95% confidence interval [CI], 9.8 to 23.8) and a median OS of 56.4 months (95% CI, 38.1 to 74.7). The ORR was 36.9% for the 84 patients with measurable lesions. Multivariate analysis revealed symptomatic visceral disease (hazard ratio, 3.437; 95% CI, 1.576 to 7.495; p=0.002) and a disease-free interval ≤ 2 years (hazard ratio, 2.697; 95% CI, 1.262 to 5.762; p=0.010) were independently associated with shorter PFS. However, sensitivity to adjuvant hormone treatment was not related to PFS. Letrozole was generally well tolerated.
  
  
  CONCLUSIONS
  Letrozole showed considerable efficacy and tolerability as a first-line treatment in postmenopausal patients with HR-positive MBC.
authors.affiliation: Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Seung Hoon
authors.initials: SH
authors.lastname: Beom
authors.affiliation: Department of Internal Medicine, CHA Bundang Medical Center, CHA University, Seongnam, Korea.
authors.forename: Jisu
authors.initials: J
authors.lastname: Oh
authors.affiliation: Department of Internal Medicine, Seoul National University Hospital, Seoul, Korea.|Cancer Research Institute, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Tae-Yong
authors.initials: TY
authors.lastname: Kim
authors.affiliation: Department of Internal Medicine, Seoul National University Hospital, Seoul, Korea.|Cancer Research Institute, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Kyung-Hun
authors.initials: KH
authors.lastname: Lee
authors.affiliation: Department of Internal Medicine, Seoul National University Hospital, Seoul, Korea.|Cancer Research Institute, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Yaewon
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Department of Internal Medicine, Seoul National University Hospital, Seoul, Korea.
authors.forename: Koung Jin
authors.initials: KJ
authors.lastname: Suh
authors.affiliation: Department of Internal Medicine, Seoul National University Hospital, Seoul, Korea.|Department of Surgery, Seoul National University Hospital, Seoul, Korea.
authors.forename: Hyeong-Gon
authors.initials: HG
authors.lastname: Moon
authors.affiliation: Department of Internal Medicine, Seoul National University Hospital, Seoul, Korea.|Cancer Research Institute, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Sae-Won
authors.initials: SW
authors.lastname: Han
authors.affiliation: Department of Internal Medicine, Seoul National University Hospital, Seoul, Korea.|Cancer Research Institute, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Do-Youn
authors.initials: DY
authors.lastname: Oh
authors.affiliation: Department of Internal Medicine, Seoul National University Hospital, Seoul, Korea.|Department of Surgery, Seoul National University Hospital, Seoul, Korea.
authors.forename: Wonshik
authors.initials: W
authors.lastname: Han
authors.affiliation: Department of Internal Medicine, Seoul National University Hospital, Seoul, Korea.|Cancer Research Institute, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Tae-You
authors.initials: TY
authors.lastname: Kim
authors.affiliation: Department of Internal Medicine, Seoul National University Hospital, Seoul, Korea.|Department of Surgery, Seoul National University Hospital, Seoul, Korea.
authors.forename: Dong-Young
authors.initials: DY
authors.lastname: Noh
authors.affiliation: Department of Internal Medicine, Seoul National University Hospital, Seoul, Korea.|Cancer Research Institute, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Seock-Ah
authors.initials: SA
authors.lastname: Im
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D047072:Aromatase Inhibitors / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D014408:Biomarkers, Tumor; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000378:metabolism* / Q000401:mortality / Q000473:pathology; D003131:Combined Modality Therapy; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D053208:Kaplan-Meier Estimate; D000077289:Letrozole; D008875:Middle Aged; D009362:Neoplasm Metastasis; D009570:Nitriles / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D017698:Postmenopause; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism; D011960:Receptors, Estrogen / Q000378:metabolism*; D011980:Receptors, Progesterone / Q000378:metabolism*; D056910:Republic of Korea; D016019:Survival Analysis; D016896:Treatment Outcome; D014230:Triazoles / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*
chemical_list: D000970:Antineoplastic Agents; D047072:Aromatase Inhibitors; D014408:Biomarkers, Tumor; D000077289:Letrozole; D009570:Nitriles; D018719:Erb-b2 Receptor Tyrosine Kinases; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D014230:Triazoles
keywords: First-line treatment; Hormone receptor-positive; Korea; Letrozole; Metastatic breast cancer