title: Positive spillover effects of prescribing requirements: increased cardiac testing in patients treated with trastuzumab for HER2+ metastatic breast cancer.
abstract: BACKGROUND
  Cardiotoxicity is a concern in patients on trastuzumab therapy, and cardiac function assessment is a recommended practice. In 2006, trastuzumab was publically subsidised for human epidermal growth factor receptor-2 early stage breast cancer with a requirement for cardiac testing prior to and during treatment.
  
  
  OBJECTIVE
  To investigate the spillover effects of this requirement on testing rates in metastatic patients treated with trastuzumab where no monitoring requirements are applied.
  
  
  METHODS
  We examined cardiac testing (echocardiography or multiple-gated acquisition scan) in 3779 women with metastatic breast cancer receiving trastuzumab between December 2001 and February 2010 and used interrupted time-series analyses to estimate changes in testing rates. The main outcome measures were the proportion of eligible patients, by quarter, receiving a cardiac function test pretreatment and during trastuzumab therapy.
  
  
  RESULTS
  Only 21% of women had a cardiac function test pretreatment, and 47% were tested at some point during the first year of trastuzumab therapy. The introduction of mandatory cardiac testing for early breast cancer was associated with an immediate 8% increase (95% confidence interval, 2-14%) in pretreatment cardiac testing and an immediate 7% increase (95% confidence interval, 4-10%) in testing during therapy in metastatic patients. Testing rates during therapy increased steadily from early 2005, coinciding with the release of interim results from several trastuzumab trials reporting cardiac-safety outcomes.
  
  
  CONCLUSIONS
  The introduction of mandatory cardiac testing for early stage disease spilled over to the metastatic setting. While deviation from guidelines may be warranted in some cases, this study suggests underutilisation of cardiac testing among patients treated with trastuzumab in the metastatic setting.
authors: Department of Population Medicine, Harvard Medical School and Harvard Pilgrim Health Care Institute, Boston, MA, USA.
authors: C Y
authors: CY
authors: Lu
authors: P
authors: P
authors: Srasuebkul
authors: A K
authors: AK
authors: Drew
authors: R L
authors: RL
authors: Ward
authors: S-A
authors: SA
authors: Pearson
mesh_terms: D000230:Adenocarcinoma / Q000737:chemistry / Q000188:drug therapy / Q000556:secondary*; D061067:Antibodies, Monoclonal, Humanized / Q000009:adverse effects* / Q000627:therapeutic use; D001315:Australia; D001943:Breast Neoplasms / Q000737:chemistry / Q000188:drug therapy*; D002173:Cancer Care Facilities / Q000706:statistics & numerical data; D009202:Cardiomyopathies / Q000139:chemically induced* / Q000175:diagnosis / Q000517:prevention & control; D017024:Chemotherapy, Adjuvant; D016903:Drug Monitoring / Q000379:methods; D004452:Echocardiography / Q000706:statistics & numerical data; D005260:Female; D015637:Gated Blood-Pool Imaging / Q000706:statistics & numerical data; D019983:Guideline Adherence; D006334:Heart Function Tests / Q000706:statistics & numerical data*; D006801:Humans; D007356:Insurance, Pharmaceutical Services / Q000331:legislation & jurisprudence*; D058990:Molecular Targeted Therapy / Q000009:adverse effects; D009313:National Health Programs / Q000331:legislation & jurisprudence*; D009363:Neoplasm Proteins / Q000032:analysis; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000032:analysis; D000068878:Trastuzumab
chemical_list: D061067:Antibodies, Monoclonal, Humanized; D009363:Neoplasm Proteins; D018719:Erb-b2 Receptor Tyrosine Kinases; D000068878:Trastuzumab; C508053:ERBB2 protein, human