Los pacientes portadores de prótesis totales de cadera metálicas no tienen un mayor riesgo de cáncer que los portadores de prótesis con superficies de apoyo no metálicas

http://www.bmj.com/content/344/bmj.e2383

Los pacientes portadores de prótesis totales de cadera metálicas no tienen un mayor riesgo de cáncer que los portadores de prótesis con superficies de apoyo no metálicas.

BMJ, 03/04/2012, 

“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”.

La prótesis total de cadera se asocia con la liberación de cobalto, cromo y molibdeno y hay evidencias de que la exposición elevada a los iones metálicos se asocia con un aumento de la incidencia de ciertos cánceres. Este estudio británico pretende determinar si el uso de superficies de soporte de metal-metal se asocia con un aumento del diagnóstico de cáncer en los primeros años después del reemplazo total de cadera y, específicamente, con un aumento en el melanoma maligno, de próstata, hematológicos y de las vías urinarias. Se siguió a 40.576 pacientes con reemplazo de cadera de superficies de contacto metal-metal y 248.995 con rodamientos de distinto material. Se observó que la incidencia de nuevos diagnósticos de cáncer fue baja después de la artroplastia de cadera (1,25% en un año, 95% IC 1,21% a 1,30%) y menor que el previsto de la misma edad y sexo de la población normal (1,65%, 1,60% a 1,70%). Comparando con los rodamientos de materiales alternativos, no se encontró evidencia de que la superficie metal-metal se asociara con un mayor riesgo de cualquier diagnóstico de cáncer en los siete años después de la cirugía, con una media de seguimiento de tres años (67.361) de los pacientes observados durante cinco años o más. Tampoco hubo un aumento en el riesgo de melanoma maligno, cáncer de próstata, hematológico o cánceres de las vías urinarias. Estos datos son alentadores, pero son resultados de un estudio observacional con seguimiento a corto plazo. Así, es necesario seguir investigando los efectos de la exposición a metales ortopédicos a más largo plazo, puesto que algunos tipos de cáncer tienen un largo período de latencia.

http://www.bmj.com/content/344/bmj.e2383

RESEARCH

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.

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