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 statisticsBMJ 2012; 344 doi: https://doi.org/10.1136/bmj.e2383 (Published 03 April 2012) Cite this as: BMJ 2012;344:e2383
- Alison J Smith, statistician1,
- Paul Dieppe, chair of clinical education research2,
- Martyn Porter, consultant orthopaedic surgeon3,
- Ashley W Blom, professor and head of orthopaedic surgery1
- on behalf of the National Joint Registry of England and Wales
- 1Musculosketal Research Unit, School of Clinical Sciences, University of Bristol, Avon Orthopaedic Centre, Bristol BS10 5NB, UK
- 2Peninsula Medical School, Universities of Plymouth and Exeter, University of Exeter, Exeter EX1 2LU
- 3Centre for Hip Surgery, Wrightington Hospital, Wigan, Lancashire WN6 9EP
- Correspondence to: A Smith
- Accepted 26 March 2012
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.
Design 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.
Setting National Joint Registry of England and Wales (NJR) linked to NHS hospital episode statistics data.
Participants 40 576 patients with hip replacement with metal-on-metal bearing surfaces and 248 995 with alternative bearings.
Main outcome measures 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.
We thank the patients and staff of all the hospitals who have contributed data to the National Joint Registry. We are grateful to the Healthcare Quality Improvement Partnership, the National Joint Registry Steering Committee, and staff at the NJR Centre for facilitating this work. The views expressed represent those of the authors and do not necessarily reflect those of the National Joint Registry Steering Committee or the Health Quality Improvement Partnership who do not vouch for how the information is presented. We are grateful to Emma Clark for her assistance.
Contributors: AJS undertook the data analysis, designed the study, interpreted the data, and drafted the paper. PD designed the study, interpreted the data, and drafted the paper. MP drafted the paper. AWB undertook the literature review, designed the study, interpreted the data, and drafted the paper. AWB is guarantor.
Funding: This study was funded by the National Joint Registry for England and Wales Steering Committee (NJRSC) as one of several specialist topic areas included in its ongoing work programme. MP is a member of the NJRSC and is chair of the Editorial Board. Decisions over the design, data analysis, and data interpretation were made independently by the authors. The decision to submit for publication was made by AWB.
Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: MP receives royalties from the manufacturer DePuy for a cemented hip prosthesis.
Ethical approval: Not required.
Data sharing: Access to data is available from the National Joint Registry for England and Wales.
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