title: Evaluating the feasibility of performing window of opportunity trials in breast cancer.
abstract: BACKGROUND
  The waiting period to surgery represents a valuable "window of opportunity" to evaluate novel therapeutic strategies. Interventional studies performed during this period require significant multidisciplinary collaboration to overcome logistical hurdles. We undertook a one-year prospective window of opportunity study to assess feasibility.
  
  
  METHODS
  Eligible newly diagnosed postmenopausal, estrogen receptor positive breast cancer patients awaiting primary surgery received anastrozole daily until surgery. Feasibility was assessed by (a) the proportion of patients who consented and (b) completed the study. Comparison of pre- and poststudy Ki67 labelling index and cleaved caspase 3 scores (CC3) was performed.
  
  
  RESULTS
  22/131 (16.8%) patients were confirmed eligible and 20/22 (91%) patients completed the study. 19/20 (95%) patients agreed to undergo optional additional tissue biopsies. The mean duration of anastrozole use was 24.7 (15-44) days. There were a statistically significant decline in mean Ki67 indices of 48.8% (p < 0.001) and a trend towards significance in the decline of CC3 (p = 0.17) when comparing pre- with posttreatment values.
  
  
  CONCLUSIONS
  window of opportunity trials in breast cancer are a feasible way of assessing the biologic efficacy of different therapies in the presurgical setting. The majority of eligible women were willing to participate including undergoing additional tissue biopsies.
authors: Division of Surgical Oncology, Department of Surgery, Ottawa Hospital, Ottawa, ON, Canada ; Cancer Therapeutics Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada.
authors: Angel
authors: 0000-0002-1546-3548
authors: A
authors: Arnaout
authors: Division of Anatomical Pathology, Ottawa Hospital, Ottawa, ON, Canada.
authors: Susan
authors: 0000-0003-0479-6651
authors: S
authors: Robertson
authors: Division of Medical Oncology, Department of Medicine, Ottawa Hospital and Ottawa Hospital Cancer Center, Ottawa, ON, Canada.
authors: Iryna
authors: I
authors: Kuchuk
authors: Division of Medical Oncology, Department of Medicine, Ottawa Hospital and Ottawa Hospital Cancer Center, Ottawa, ON, Canada.
authors: Demetrios
authors: 0000-0003-4592-3346
authors: D
authors: Simos
authors: Department of Oncology, McMaster University, Hamilton, ON, Canada.
authors: Gregory R
authors: GR
authors: Pond
authors: Cancer Therapeutics Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada.
authors: Christina L
authors: CL
authors: Addison
authors: Division of Surgical Oncology, Department of Surgery, Ottawa Hospital, Ottawa, ON, Canada.
authors: Mehrzad
authors: M
authors: Namazi
authors: Cancer Therapeutics Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada ; Division of Medical Oncology, Department of Medicine, Ottawa Hospital and Ottawa Hospital Cancer Center, Ottawa, ON, Canada.
authors: Mark
authors: M
authors: Clemons
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000077384:Anastrozole; D018931:Antineoplastic Agents, Hormonal / Q000627:therapeutic use*; D014408:Biomarkers, Tumor / Q000378:metabolism; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000601:surgery; D018270:Carcinoma, Ductal, Breast / Q000188:drug therapy* / Q000378:metabolism / Q000601:surgery; D017024:Chemotherapy, Adjuvant; D004334:Drug Administration Schedule; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008408:Mastectomy; D008875:Middle Aged; D020360:Neoadjuvant Therapy; D009570:Nitriles / Q000627:therapeutic use*; D010865:Pilot Projects; D011446:Prospective Studies; D014230:Triazoles / Q000627:therapeutic use*
chemical_list: D018931:Antineoplastic Agents, Hormonal; D014408:Biomarkers, Tumor; D009570:Nitriles; D014230:Triazoles; D000077384:Anastrozole