title: Risk of cancer in first seven years after metal-on-metal hip replacement compared with other bearings and general population: linkage study between the National Joint Registry of England and Wales and hospital episode statistics.
abstract: OBJECTIVE
  To determine whether use of metal-on-metal bearing surfaces is associated with an increased risk of a diagnosis of cancer in the early years after total hip replacement and specifically with an increase in malignant melanoma and haematological, prostate, and renal tract cancers.
  
  
  METHODS
  Linkage study with multivariable competing risks flexible parametric survival model to examine the incidence of new diagnoses of cancer in patients with metal-on-metal hip replacement compared with those with alternative bearings and to compare the observed incidence of diagnoses in patients undergoing hip replacement with that predicted by national incidence rates in the general population.
  
  
  METHODS
  National Joint Registry of England and Wales (NJR) linked to NHS hospital episode statistics data.
  
  
  METHODS
  40,576 patients with hip replacement with metal-on-metal bearing surfaces and 248,995 with alternative bearings.
  
  
  METHODS
  Incidence of all cancers and incidence of malignant melanoma and prostate, renal tract, and haematological cancers.
  
  
  RESULTS
  The incidence of new diagnoses of cancer was low after hip replacement (1.25% at one year, 95% confidence interval 1.21% to 1.30%) and lower than that predicted from the age and sex matched normal population (1.65%, 1.60% to 1.70%). Compared with alternative bearings, there was no evidence that metal-on-metal bearing surfaces were associated with an increased risk of any cancer diagnosis in the seven years after surgery (mean follow-up of three years, 23% (n=67,361) of patients observed for five years or more). Similarly, there was no increase in the risk of malignant melanoma or haematological, prostate, and renal tract cancers. The adjusted five year incidence of all cancers for men aged 60 was 4.8% (4.4% to 5.3%) with resurfacing, 6.2% (5.7% to 6.7%) with stemmed metal-on-metal, and 6.7% (6.5% to 7.0%) for other bearing surfaces. Equivalent rates for women aged 60 were lower: 3.1% (2.8% to 3.4%) with resurfacing, 4.0% (3.7% to 4.3%) with stemmed metal-on-metal, and 4.4% (4.2% to 4.5%) with other bearings.
  
  
  CONCLUSIONS
  These data are reassuring, but the findings are observational with short follow-up. The use of hospital episode statistics data might underestimate cancer diagnoses, and there is the possibility of confounding by indication. Furthermore, as some cancers have a long latency period it is important that we study the longer term outcomes and continue to investigate the effects of exposure to orthopaedic metals.
authors.affiliation: Musculosketal Research Unit, School of Clinical Sciences, University of Bristol, Avon Orthopaedic Centre, Bristol BS10 5NB, UK. alison.smith@bristol.ac.uk
authors.forename: Alison J
authors.initials: AJ
authors.lastname: Smith
authors.forename: Paul
authors.initials: P
authors.lastname: Dieppe
authors.forename: Martyn
authors.initials: M
authors.lastname: Porter
authors.forename: Ashley W
authors.initials: AW
authors.lastname: Blom
mesh_terms: D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects* / Q000295:instrumentation; D003625:Data Collection; D004739:England / Q000453:epidemiology; D005260:Female; D005500:Follow-Up Studies; D019337:Hematologic Neoplasms / Q000453:epidemiology*; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D015994:Incidence; D008297:Male; D008545:Melanoma / Q000453:epidemiology*; D008670:Metals / Q000009:adverse effects; D011471:Prostatic Neoplasms / Q000453:epidemiology*; D011474:Prosthesis Design; D012042:Registries / Q000706:statistics & numerical data; D012307:Risk Factors; D014571:Urologic Neoplasms / Q000453:epidemiology*; D014852:Wales / Q000453:epidemiology
chemical_list: D008670:Metals