I am a bit reluctant to write this post as I don’t want to scare people. Morphine based pain killers are often used to treat cancer pain and this recent news report does not change any treatment your consultant or doctor may have prescribed.
This week the BBC news website had a story “Morphine might ‘might spread cancer‘”, which is based on research carried out at the University of Chicago in the States (you can read the University of Chicago press release here).
Why am I hesitant to write about this research? Well, research comes in lots of different forms and unless you are working in science it can be hard to sort out good research from bad research. As if that isn’t hard enough, trying to work out which research is promising but very preliminary (the sort of research that will interest other scientists) and which research is based on large scale studies involving hundreds of people (the sort that will interest patients) is a difficult thing to do.
This study into morphine and cancer cell growth is good science, but it is a very preliminary result, that means that more scientists need to try and repeat these experiments to see if they get the same result. They also need to repeat these experiments on more people to make sure the result is true and not down to chance.
Why else am I skeptical of this news report? Well it was written from a press release. Universities are in the business of attracting students (and grant funding), so they, quite rightly, like to publicise their achievements. However, scientists don’t work from press releases, they need to see the data published in a peer reviewed scientific journal (basically a magazine where several different independent scientists check your work to see if they think it’s reasonable, before publishing it).
The information about morphine encouraging the growth of cancer cells has not, as far as I can tell, been published in a journal (although I am sure it will be). The press release was written because the information is being given at a scientific conference. It is easier to present your work at a scientific conference than publish it in a journal, this is not a bad thing, conferences are supposed to provoke debate and make you think, but until data has been published in a journal other scientists can’t study it and work out if the research is good (or not).
So what does this research show? We know that in isolated tumour cells grown in a plastic dish, in a lab, that morphine makes them grow faster (proliferate). Cells know that morphine is there because on their outside they have something called a “morphine receptor”. There are 3 different types of morphine receptor called mu, kappa and delta (they could have called them 1,2 & 3 but scientists like to make things sound difficult). It’s a bit like having a mobile phone mast on a hill that can receive signals from BT, vodaphone and orange.
The scientists in Chicago studied lung cancer cells, they treated the cells with a drug called methylnaltrexone, which stops the mu morphine receptor working (but the other two, kappa and delta aren’t affected). They found that the tumour cells didn’t grow as fast if they were treated with methylnaltrexone and morphine. Methylnaltrexone also stopped lung cancer cells growing in mice.
Why is this result important? The drug methylnaltrexone was approved for use in the UK in 2008. One of the side effects of morphine based painkillers is constipation, researchers think that the constipation is caused by activating the mu morphine receptors in the gut. Importantly, the pain killing effect of morphine is thought to be caused by the kappa and delta receptors in the brain. The idea is that methylnaltexone will help relieve constipation caused by morphine but importantly, the morphine will still work as a painkiller.
What does this mean? It means we already have a drug that may help stop morphine making tumours grow and we need to do clinical research, in patients to see if using methylnaltrexone helps slow down tumour growth in people receiving morphine.
What if you are having treatment for cancer now? This research does not alter any of the current treatment guidelines, but it is interesting and hopefully will pave the way for better treatments in the future. As Cancer Research UK said
Much more research would be needed to justify changing the way opiates are used to treat people with cancer.
If you are more impressed with the images than the text “
