Saturday, April 7, 2012

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

Just published.  This study was designed to look at the incidence of cancer during the first 7 years after MOM hips were implanted.  The results showed pretty much the same information as did the Swedish studies; not much activity in this short term.
 
The conclusion basically warns that this is only short term data and it is important that we study the longer term outcomes and continue to investigate this issue.
 
A couple of things that should be noted:
-"hip patients are not routinely screened for cancer.  It is likely that a targeted screening programme would identify more patients with cancer than were identified here."  [ yes, I agree.]
 
- while this article mentions that the results should "reassure patients", I am not reassured at all.  there is too much research that has set the stage for the cancer issue to be dismissed even in the short term.
 
-"patients who have undergone joint replacement have a higher than normal incidence of DNA damage to blood lymphocytes.  In concentrations found in the blood after hip replacement, cobalt and chromium have the ability to signal across intact barriers in the body and cause irreversible DNA changes to cells on the other side of the barrier."
 
If you want more information on this research, here are some links:  http://www.mydepuyhiprecall.com/2012/03/response-to-british-orthodpedic.html
 
 
 
 
BMJ 2012; 344 doi: 10.1136/bmj.e2383 (Published 3 April 2012)
Cite this as: BMJ 2012;344:e2383
 

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.

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.

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