Thursday, January 27, 2011

Survival in cancer patients: improving the accuracy of our estimates

Survival in cancer patients: improving the accuracy of our estimates

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There's a long held belief that, as a cancer patient, the longer you survive the better you're going to do.
Professor Suzanne Chambers is the Director of Research at the Cancer Council Queensland, and has been involved in some research that has improved the accuracy of cancer patients' survival estimates.

This transcript was typed from a recording of the program. The ABC cannot guarantee its complete accuracy because of the possibility of mishearing and occasional difficulty in identifying speakers.

Norman Swan: important new information on cancer prognosis from Queensland. They've been putting numbers against the long held belief that the longer you survive, the better you're going to do.

Professor Suzanne Chambers is Director of Research at the Cancer Council Queensland.

Suzanne Chambers: What the study does is it looks at what's called conditional probability of survival.

Norman Swan: My eyes are glazing.

Suzanne Chambers: I'm not surprised. Well if you're diagnosed with cancer when you see your doctor he will give you a percentage estimate of your chance of still being alive in 5 years and obviously that's critical information to people. What people may not realise though is that that estimate changes over time such that the longer you survive as the years pass your percentage estimate of survival actually improves and goes up.

Survival probabilities are not a static phenomena and what this study does ....

Norman Swan: When you ask the question 2 years down the track after diagnosis and treatment the answer actually is different although doctors might not tell you so.

Suzanne Chambers: That's right. Well the reason why they may not tell you so is they haven't had that data so what we have done is analysed Queensland data to be able to provide that information for a whole range of cancers.

Norman Swan: So tell me what you did and what you found?

Suzanne Chambers: Well we recalculated their probability estimates and found that over ...........

Norman Swan: Sorry, just before you go on, you calculated this presumably from the cancer registry where everybody with cancer, in fact in every state in Australia is put down in a register and their progress followed.

Suzanne Chambers: That's right, we used D-identified cancer registry data, used quite sophisticated statistical techniques.

Norman Swan: And what did they find?

Suzanne Chambers: What they found is that over time people's survival chances improved which is of course excellent news. It's not even across all cancer sites so if not surprisingly if you start out with a very good chance of survival in 5 years time it's better but not as greatly improved as if you start out with quite low chances of survival. So people who have poorer prognoses or more serious cancers do get better improvements the longer they live.

Norman Swan: So you're coming off a low base therefore any improvement looks bigger?

Suzanne Chambers: Yes that's right, and of course there are limitations to this data as well. At this point in time our cancer registries unfortunately do not record the stage of disease reliably across all cancers and it's something that everybody is working on and it's critical that that occur. And the more we get that the more detail we'll be able to provide this information because people want to know this.

Norman Swan: And by stage of disease you mean how far it's spread, how big the tumour is before you start that kind of diagnosis.

Suzanne Chambers: That's right, how advanced your cancer is before you start because that will obviously have an impact on the numbers as well. It's important to be aware that these are just numbers even though these are better numbers and so there is always an element of uncertainty for people but people do search for this information just to help guide their thinking about the future. And we think it's important that they have realistic estimates and where there is some good news they need to know that.

Norman Swan: So give me some examples for the tumours you looked at and the difference it makes from time of diagnosis to say 5 or 10 years out.

Suzanne Chambers: Sure. Well the cancers that have an initially poorer prognosis is pancreatic cancer and lung cancer have the greatest improvements. So at diagnosis the 5 year survival estimates for those are 7% and 14% respectively. Once they have survived 3 years their 5 year conditional survival goes up to 63% and 59% respectively.

Norman Swan: Wow, that's a huge change.

Suzanne Chambers: It's a huge change; it's not as large a change with cancer that have a high survival rate to start with so for melanoma it goes up from 94% to 96%. People do say that once you get up to a 95% survival rate you're the same as the general population. So I think even those pieces of good news can give people realistic hope.

Norman Swan: Because not all of us are going to survive the next 5 years for whatever reason.

Suzanne Chambers: That's exactly right.

Norman Swan: So let's look at some common tumours like breast cancer and colorectal cancer, bowel cancer.

Suzanne Chambers: Sure. So for breast cancer at diagnosis 88% and that goes up 3 years after diagnosis to 90.1%. For colorectal cancer it's at diagnosis 65.9%, 3 years after diagnosis that's up to 87.1% and if you get 10 years that's 99.2%. So it's a progressive improvement.

Norman Swan: As you said earlier these are averages so that you don't know what happens if you've got say breast cancer and they've picked up 3 lymph nodes in your armpit and the tumour was a little bit large and your prognosis is a little bit less. In theory if you get to 3 years in that situation you don't really know what the increased prognosis is but it could be like pancreatic cancer, it could be quite dramatic.

Suzanne Chambers: Look it's hard to know from the data that we've got but over time as we start collecting more detailed information in cancer registries we'll be able to make better picks. Certainly it would be reasonable to suggest that because we get larger improvements with pancreatic and lung cancer that people who have a more advanced cancer at diagnosis would get larger improvements the longer they live.

Norman Swan: And again you don't separate this by country and city because there is evidence in Queensland and in other states that people who live outside the major cities don't do as well with their cancers.

Suzanne Chambers: That's exactly right; we have for several cancers there are rural differentials where we have places in Queensland where early detection is less and where mortality is worse. Is the reason why they did more because they live further from the tertiary treatment centre or is it because they are further from their GP or is it because of certain aspects about them as an individual?

Norman Swan: In NSW they tied it down to that people in the country are diagnosed later which puts the finger on GPs and others that they are not picking up these cancers as early as their colleagues in the city.

Suzanne Chambers: It could be that, if someone is not getting diagnosed earlier it could be that there's something about the environment they're living in that makes it physically more difficult to get that care or it could be something about their own attitudes or other risk factors that they have.

Norman Swan: So if somebody's listening and they've been diagnosed with cancer and they seem to be doing well and they want to know what their changing circumstances are is this information publicly accessible?

Suzanne Chambers: Well it's in the Medical Journal of Australia so you would just get onto that journal's site and you would search for it there. We've already had an email from a consumer who had colorectal cancer who saw this, looked it up and found it terribly helpful and had been looking indeed for this sort of information so it's there and it's readily accessible for people. But what they should also remember is there is a cancer helpline nationally - 13 1120 is the number where they can ring and talk to trained health professionals who can answer their questions and lead them to more useful information.

Norman Swan: And we'll have the link to the Medical Journal of Australia article on the Health Report's website . Professor Suzanne Chambers is Director of Research at the Cancer Council Queensland. And you're listening to the Health Report here on ABC Radio National with me Norman Swan.

Also On The Program;
Norman Swan; Thanks and welcome to the program. This morning on the Health Report some certainty for parents about the right way to diagnose and treat young children who have a middle ear infection. Plus are Australians eating their bread following the addition of folate to our flour supply - some results from mass blood tests. Does putting the number of calories and fat content on the menu of fast food outlets make you head for the salad option - some interesting findings.
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