Drop in breast cancer mortality in developed countries varies

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Published: 19 Dec 2013
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Dr Donald Berry - MD Anderson Cancer Center, Houston, USA

Dr Donald Berry talks to ecancertv at SABCS 2013 about the changes in breast cancer mortality in developed countries such as the UK, USA and Japan over the last 50 years, due to screening, improved treatment and changing environmental factors.

My presentation at the San Antonio meetings addressed the incidence but, most especially, the mortality in the world focussing on industrialised countries and the various studies that have come to bear on that, national registries of course, but also simulations and modelling to try to understand what is it that has caused the changes and, in particular, the drops in mortality in many industrialised nations.

So, for example, in Europe most of the countries have seen a fall in breast cancer mortality led by the UK where the drop has been since 1990 until about 2008 was 36%. The United States is about 30%; if we go across the world to Australia it was about the same so they look very similar. In other industrialised countries, in Japan for example, the rate has been very low historically, only about an eighth or ninth of what it has been in the United States or the United Kingdom and it has increased. Going back to Europe, some of the European countries have seen increases, the Baltics in particular which is interesting. They have a similar characteristic to Japan, namely that their rates are very low relative to the rest of the world and they’ve seen increases. Roughly speaking, the countries that have had historically low rates have seen increases or stable mortality and the countries such as the US and UK that have seen major drops have experienced high rates in the past.

An interesting aspect is to try to compare this with incidence. You’d think that if incidence were to go up that maybe mortality would go up but it doesn’t. So screening comes into play, screening has increased the incidence of breast cancer over the course of the last twenty years in many industrialised countries, certainly most of Europe, but at the same time there have been treatment advances so pulling those two apart and trying to understand what is it that’s causing the drop in many of these countries, is it screening, is it treatment, is it both? So my presentation tried to address that question and I’ve written about it and published studies that address it in part through something called the CISNET, Cancer Intervention and Surveillance Network, which is mainly the United States but we have one of our modellers, there are six models of breast cancer and one of them is in the Netherlands in Erasmus University. So we tried to model breast cancer in the United States, including the Netherlands group is modelling the US mortality and we pulled together various sources of information to try to reconstruct an individual woman’s experience with screening, within if she gets breast cancer what happens to her? What is the stage? What is the treatment? What is the course of the disease? We got different results at the time with the seven models, we started this about ten years ago, we got seven different answers but they were very comparable in a sense. Things are changing in the world; screening is not changing much, we’ve stabilised here in the United States, the screening in these industrialised countries has stabilised at some level of maybe 60% or 70% of women getting regular screening over the ages of 50-70 or so, the prime area where screening comes into play. At least my model concluded that much of the mortality reduction is due to treatment: about a third to screening and two-thirds to treatment. There may be some other environmental factors that have changed over time and, looking to the Japan thing and the Baltic thing, maybe that’s true but exactly what they are is not clear.

So there’s not much screening in Japan and what is it? I think it’s all theory. The Japanese diet has no doubt changed over the course of the last fifty years so this is a fifty year change that’s doubling in mortality but it started out fifty years ago it was about 5 per 100,000 whereas in the UK and the US it’s about 45 per 100,000. So we’ve seen in the UK and US and other countries rather substantial drops from these high levels. Is it diet? Have they changed? Is cancer understood differently? Is the diagnosis better? Is the attribution of mortality to one cause of death better? I don’t know and I don’t know that anybody really knows. We do know that when people move, say, to the United States from the Far East that they come with a low incidence of breast cancer and a low mortality due to breast cancer. When they get here they adopt, in addition to some of the other good and bad things that we have, they adopt the mortality of our country which is interesting and suggests that there are environmental things that go beyond the differences in genetics.