Tuesday 4 October 2011

Beta blockers and cancer

There was a recent flurry of headlines about possible new uses of beta blockers - normally prescribed for high blood pressure - and that they might have anticancer properties. For example the BBC headlined the story as Beta blockers 'may stop breast cancer spreading'. The trigger for the story was the announcement an analysis of 800 patient records showed that those cancer patients who had also been treated with beta blockers had lower rates of metastatic disease - in other words there are indications that beta blockers stop or slow breast cancer from spreading to other parts of the body. The real headline is from the abstract of the paper that reported the results:

In addition, there was a 57% reduced risk of metastasis, and a 71% reduction in breast cancer mortality after 10 years. This proof-of-principle study showed beta-blocker therapy significantly reduces distant metastases, cancer recurrence, and cancer-specific mortality in breast cancer patients suggesting a novel role for beta-blocker therapy
This is not the first report on beta blockers and cancer - for example there was also a very recent study looking at beta blockers and malignant melanoma. That study concluded:

Increased survival time of patients with melanoma receiving beta-blockers suggests that use of this drug may hold promise in treatment strategy for these patients.Impact: The observations described here suggest that catecholamines may retard melanoma progression and that beta-blockers may have unrecognized potential as a therapeutic intervention for melanoma.

These two studies are both epidemiological studies - they look at populations of patients and compare outcomes based on differences in medication, exercise, diet or whatever else the scientists are looking at. What these studies can do is find correlations - one thing is associated with another. What they can't do is directly show causation - that one thing causes another. So, in this case the scientists can see a relationship between beta blocker use and disease outcomes in cancer patients (or, strictly speaking, breast cancer and malignant melanoma).

However, in this case there is additional supporting evidence that is of significance. Firstly there are in vitro studies that look the effects of beta blockers on cancer cells in the test tube. And yep, the findings are that beta blockers can slow the proliferation of different types of cancers cells in the test tube, that they can enhance the response to some chemotherapy drugs and radiation and that these results are for a range of cancers, including brain and gastric cancers.

This is all positive because these beta blocker drugs have been in use for a long time and in large populations. It means that scientists can by-pass the long and tortuous process of doing phase I clinical trials. We already know about the long term safety of these drugs, we know about dosing and these aren't new compounds that have significant price tags attached.

What we need now is to quickly move on from the epidemiological studies and start the process of clinical trials now. In particular, in those breast cancer patients in remission and those whose disease has not metastasised should be pushing hard for clinical trials now, not in two or three or four years time. There needs to be a sense of urgency about these things. Time is a luxury that doctors can afford, but not their patients.

Finally, it is worth pointing out that beta blockers are just example of 'off-label' usage of existing drugs for cancer sufferers. Off-label use of drugs is important precisely because we by-pass the years of waiting for phase I results. Other good examples, some of which I will explore in future articles, include the anti-diabetic drugs metformin and pioglitazone, the anti-inflammatory celecoxib and the cough medicine noscapine.

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