Wednesday 9 May 2012

The Wrong Models of Cancer - Part 2

In the first part of this article I discussed one aspect of how researchers have modelled cancer in the test tube and how this has been a factor in the slow progress in 'the war on cancer'. To recap quickly, by ignoring the evolutionary processes taking place in cancer cell lines, in petri dishes and in implanted tumours, researchers are often surprised that what works in a lab doesn’t translate to the clinic. They’ve been targeting a different type of cancer cell to the ones that affect people. A tumour is more than a blob of a single type of deranged cell. It’s an entire eco-system of  'cancer' cells, the surrounding tissue (the stroma), disordered blood vessels, immune cells and so on.

But this is not the only type of wrong model. There is another that has had equally disastrous results – and it begins with the very phrase 'the war on cancer'. This metaphor of cancer as a war reflects the belief that the only way to deal with cancer is to eradicate it completely. Cancer cells have to be destroyed once and for all, and therefore the most radical and demanding treatments are used. Our current range of cancer treatments are some of the most demanding and dangerous in medical practice. Radical surgery, toxic chemotherapy, burning with radiation… These treatments are barbaric but it’s the best we have so long as the intention is to go in and kill every single cancer cell that exists.

This approach makes sense if we believe that there is no alternative. If your mental model of cancer is that it is always and everywhere a killer, then of course there is no alternative. And those of us who have seen loved ones struggling against the disease will find it hard to think of cancer as anything other than a killer. But is this a valid assumption - is it always a killer?

There is an emerging scandal in the world of cancer treatment that is slowly starting to get more publicity and to gain more public awareness. The fact is that there are thousands of women being treated for breast cancer that has been caught by mammography screening. There are thousands of men being treated for prostate cancer that has been diagnosed after screening. These people haven’t been misdiagnosed – the cancers that have been discovered are real enough – what they are victims of is overdiagnosis.

The truth is that some cancers do not develop. They will grow for a while, enough to be picked up on a routine scan, but then they will spontaneously regress or else grow so slowly that they pose no real danger at all. In the jargon they will never become symptomatic. This isn’t controversial - it’s well known that more men die with prostate cancer than die of it. These men will have prostate cancer that doesn’t ever grow dangerously out of control or metastasise and colonise other organs or the bones. It is the same with breast cancer, there are some forms of the disease which do not ever grow or become dangerous.

The problem of overdiagnosis is that we don’t know which cancers are the ones that will expire or grow to nothing and those that will turn into killers. The only thing that doctors can do is treat all the cancers they find and in doing so subject those patients to the full armoury of the war on cancer.

But this model of cancer as a killer extends further than to the scandals around mammography screening and prostate cancer. What it has done is to blind researchers to an alternative way of thinking. Perhaps we should be looking at turning all cancers into the sort that do nothing. Rather than kill tumours we could perhaps look at containing them, acting on them using treatments that keep the cancers small, non-invasive and under control. We can treat cancer like we do a chronic disease, like diabetes or high blood pressure.

Cancer as a chronic disease opens a new way of thinking about the disease. The heavy guns of chemotherapy, radiotherapy and radical surgery are still there for the tumours that are invasive and out of control. But if we focus on containment first, then we have saved thousands of patients from the most horrible treatments we have ever inflicted on people.

Is any of this possible? Can we treat cancer so that it stays small and manageable? There are a number of different avenues being explored at the moment by different teams around the world. Some focus on cutting off the tumour blood supply, others look at targeting tumour metabolism to starve them, or else change the micro-environment that the tumours depend on…

There are many different ways of doing this, and the chances are that in the end it will be combinations of these different treatments that will give us what we want. One of the things that these treatments have in common is that most of them are not directly cytotoxic. In other words they don’t set out to kill cells, not even cancer cells. Instead there is a focus on one or more aspects of the tumour support system. By changing the tumour microenvironment or tackling the flow of nutrients, these treatments tip the balance away from the tumour and back to the rest of the body.

In future articles I hope to focus on some of the more avenues being explored by cancer researchers working in this area.

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