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BMJ 2006; 332 doi: (Published 25 May 2006) Cite this as: BMJ 2006;332:1264
  1. Alison Tonks, associate editor (

    Meta-analysis finds rare but serious side effects

    Randomised trials are rarely big enough, long enough, or powerful enough to give patients the information they want about rare but serious side effects. In an unusual move, researchers used meta-analysis, a powerful tool for combining trial results, to find out more about the cancer causing potential of a treatment for rheumatoid arthritis—the monoclonal antibodies infliximab and adalimumab. Both are directed against tumour necrosis factor.

    Credit: JAMA

    Pooled data from nine placebo controlled trials, which included more than 5000 patients, showed that the antibodies were associated with a significantly greater risk of cancer (odds ratio 3.3, 95% CI 1.2 to 9.1) and of serious infections (2.0, 1.3 to 3.1). Overall, 24 of the 3493 patients given monoclonal antibodies developed cancer (0.8%), compared with three of the 1512 given placebo (0.2%). Higher doses were associated with higher risk of cancer.

    These findings are consistent with what we already know about tumour necrosis factor—it helps combat infections and kills tumour cells—and with what researchers suspected might happen when it was disabled. The results are also consistent with previous hints from postmarketing surveillance, cohort studies, and individual trials.

    The authors say they are among the first to use meta-analysis to assess a drug's safety, and it works well. They suggest others follow suit.

    Low oxygen and pressure don't promote clotting

    Fifty years after someone first noticed the connection between air travel and venous thrombosis, scientists are still trying to untangle the complex relationship between haemostasis, sitting still for a long time, and the combined effects of low pressure and low oxygen tension in the cabin. In the latest controlled experiment, hypobaric and hypoxic conditions mimicking a long haul flight did not alter volunteers' haemostasis any more than sitting for eight hours in conditions mimicking a deck chair in the garden at 50-70 m above sea level. Serum markers for coagulation, …

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