Cancer Survival

There’s been a new talking point in the health care debate in the US; the cancer survival rate. Many bloggers (site, site, site, and site) and research institutes have discussed the results of a 2007 article in the medical journal Lancet Oncology that compared cancer survival rates in several different countries. The blogs and news sites claim the US is the best in the world for cancer survival and the medical journal article seems to back that up. But the United States has the lowest longevity of the industrialized nations, so there’s some cause for skepticism. Does the US have the best cancer survival rate in the world?

Death rates and survival rates are tricky things to consider because, as they say, life is 100% fatal, no one gets out of here alive, etc. Since we’re all going to die we probably don’t care so much about how we die, but rather when. Cancer researchers use two different statistics to track this: mortality rate and survival rate, each has its own strengths and weaknesses. Before we examine the study, lets take a moment to understand the terms used.

Five Year Survival rate.

leadTimeBiasYou get cancer and then within five years after you’re diagnosed you die. This includes deaths for any reason. The benefit of this is that if one gets lung cancer (for example) and dies from pneumonia because ones lungs were weakened by the cancer then it seems correct to attribute this death as being caused by the cancer. But this rate has 2 main problems. One is the “lead time bias” which is illustrated in the graph to the right.

We don’t really care how long we live after the cancer has been diagnosed, but rather how long we live since we actually got the cancer. Consider a cancer that kills everyone within 8 years of onset. Normal screening may be such that it is only caught 5 years after onset. Three years later (8 years after onset) everyone with this cancer would be dead. A 0% 5 year survival rate. If improved screening allowed doctors to detect it four years earlier then suddenly there would be a much higher five year survival rate as everyone now survives 7 years after detection. But everyone still dies 8 years after onset. The earlier detection didn’t actually change the course of the disease, the doctors just detected the cancer earlier. There is no easy way to adjust for this effect in the five year survival rate statistic.

The other problem occurs when one wants to compare survival rates between 2 different countries.  If these countries are the same in all other ways except their cancer survival rates then the “observed” survival rate could be used. But this is hardly ever the case. People in different countries die at different rates due to heart attacks, automobile accidents, pneumonia and other causes. Medical researchers adjust for this by computing the “relative” survival rate, which “subtracts out” the “background mortality” as illustrated in the graph below.

death

To illustrate, if 3 out of 1000 people aged 65 die from pneumonia in a given year (the “background” rate), but 7 out of 1000 cancer patients die from pneumonia in that same year (the “observed” rate) then it would be safe to assume that 3 of those 7 cancer-pneumonia deaths were due to natural pneumonia and 4 were due to cancer-induced pneumonia (the “relative” rate).

Mortality Rate

You die, the doctors determine the cause of death was cancer. You’re now a statistic in the mortality rate for that cancer. One problem with this statistic is it doesn’t account for cancers that weaken but do not kill you. The lung cancer-pneumonia example above would be counted as a death due to pneumonia by this measure. However, the mortality rate is able to avoid the “lead time bias” problem of the survival rate statistic.

sideBarThe reason is that the longer you live the higher your chances that something else will kill you. So if more people are dying from other causes and fewer people are dying from this cancer it’s probable that the updated detection and treatment are indeed leading toward longer life.

The Lancet study looked at 3 (or 4) different cancers, breast cancer in women, prostate cancer and colorectal cancer (sometimes separately colon cancer and rectal cancer). Below are their results.

breast

prostate

colorectalM

colorectalW
With the exception of the US, the OECD countries in the study are shown in green. The red line is the average survival for the 22 European countries studied. A few things are clear.

  • The difference in survival between most of the top countries is small, but despite that the US is clearly in the top ranks.
  • The US is also significantly ahead of the European average.

While it’s hard to say that the US is #1 or #2 in this measure since, statistically many countries are tied for the #1 and #2 positions, it is the case that of the 31 countries studied the US has better cancer survival rates than at least 25 of them. So the articles that cite the US’s superior cancer survival rates are accurate, at least for these cancers.

That’s right, many comments in the news merely state that the US has the best cancer survival rate in the world. Not strictly true for at least 2 reasons. One is we’re actually tied for first or second place, not uniformly nor uniquely #1. Also we’re #1 or #2 only for the cancers studied above. We may have inferior survival rates for other cancers and furthermore the cancers studied above may not be the most significant cancers in the US or world. Let’s analyze these concerns.

Are these the cancers that matter?

Who cares if we have a high survival rate for cancers that don’t tend to kill people or that not many people contract in the first place? Is this the case with the 3-4 cancers studied above? The American Cancer society has a report that lists the top causes of death due to cancer around the world. For developed nations their chart is shown below.

2007 Estimated Deaths in Developed Countries
Total Rank Cancer Male Deaths Female Deaths Total Deaths
1 Lung & Bronchus 465,540 173,842 639,382
2 Colon & Rectum 175,774 165,480 341,254
3 Stomach 141,218 89,620 230,838
4 Breast 203,528 203,528
5 Pancreas 78,009 72,681 150,690
6 Prostate 143,834 143,834
7 Liver 78,174 40,943 119,117

Combining the genders where appropriate to get total mortality, lung cancer is the leading cause of death by cancer in developed countries (all developed countries combined). The cancers studied in the Lancet article are ranked #2, #4 and #6 in terms of total mortality in developed nations. Additionally, breast cancer is #2 for women (#4 over all), and prostate cancer (#6 over all) is #3 for men. So the cancers studied are a reasonable cross section of the most significant cancers that affect the developed world.

Summary

The cited study in Lancet Oncology is the first to compare cancer survival statistics across many different countries. The cancers they chose were a reasonable cross section of the most significant cancers among developed nations. Strictly speaking the blogs claiming the US is #1 in cancer survival are correct. But stated in plain English, without the benefit of charts or graphs, it can be misleading. The graphs above, largely the same graphs as published in Lancet Oncology, clearly show many countries are also very close to the US in terms of cancer survival.

The implied question here is, would our #1 ranking in cancer survival be significantly harmed as a side-effect of health care reform? This is for you to decide from what’s been presented. For my part the answer appears to be “no”. The reason is that there are many countries that are very close to the US in cancer survival rates and these countries have some form of government involvement in health care. While it’s plausible that our #1 ranking in spending is related to our #1 ranking on survival, it’s important to note that we could cut our spending on health care by 40% and still be #1 in the world on spending. It’s hard to believe that such a change would significantly affect the survival ranking. Indeed, there is some recent data that supports that, regarding prostate cancer at least, the US may be over-treating (and hence over-spending on) cancer.

Cause and Effect are tricky things to argue. When you have a big cause and a big effect most folks take the conservative route and assume cause & effect until proven otherwise. But when it’s big cause and little effect, such as the case with spending and cancer survival, extreme conservatism doesn’t seem to be warranted.

17 comments for “Cancer Survival

  1. Marc Brown
    September 28, 2009 at 4:58 pm

    Bear in mind that until recently the US cancer data came from 10% of the population. Now in the latest study it’s up to 42%, and the effect of adding more registries has been to decrease survival rates. There are also striking variations according to race and insurance status.

  2. numbersguy
    September 29, 2009 at 8:53 am

    Hi Marc:
    You packed a lot of information into your short response!

    The original Lancet graphs included more information than my version of them. Theirs identified the countries that had 100% coverage from those that didn’t, and as you say the US had only 42% coverage. The other countries with less than 100% coverage were Canada, Japan, France, Italy, Spain, Netherlands, Switzerland, Germany, Austria, Portugal, Poland, Czech Republic, Brazil and Algeria, about half of the countries.

    I didn’t see any reference in the article to the US portion being more or less skewed toward those with insurance. (I suspect you may be referring to articles I haven’t seen.) But regarding data coverage, there was another whole section of the article devoted to specific cities and states in the US where close to 100% of the registries were used. For example, the US fraction included Atlanta but not Georgia, all of Colorado and all of California with additional detail for Los Angeles and San Francisco, just to name a few. In contrast, the article did mention that the portion of Italy studied was a more affluent part than the country as a whole and it mentioned Cuba as having some quality control issues with their registries (and for that reason I excluded Cuba from my version of their graphs).

    The article did mention the race variation you refer to above. However either it or other articles I researched also pointed out that the US is much more heterogeneous than the average European country. While this may weigh more favorably for the US (we’re #1 despite having a more heterogeneous population), I chose to present the original Lancet article data as is. After all, there are only 2 ways to account for this, either compare countries as a whole (what was done) or compare the predominant race in each country to that of other countries (eg, Caucasian US to Caucasian France). Fortunately data wasn’t available for the latter comparison and besides it seems off-topic to consider race specific data when trying to set policy for an entire country. (I’m not suggesting you were implying this, but you raised race so I needed to give all of my reasoning behind ignoring racial differences.)

  3. Marc Brown
    September 29, 2009 at 2:15 pm

    My feeling – in the absence of hard and fast data – is that the wider you cast the net the more truth you reveal. If you look at the Eurocare stats:

    http://www.eurocare.it/Results/tabid/79/Default.aspx

    you can see that the UK is the only large population country that is a 100% registry reporter, and is pretty brutally honest about the stats too.

    I’m not suggesting that the US is not ahead for a large section of its population, thanks to aggressive screening and top notch comprehensive cancer centres. The Lancet paper makes this clear. But the size of the effect is likely to be smaller than we can see now. A few factors being:

    – lag time – a lot has happened in the laggard countries (eg the UK) to improve cancer care in the 2000s. This registry data we are looking at is mostly from the 1990s
    – health inequalities are particularly acute in the US and as data from the American Cancer Society makes clear, blacks, Hispanics and the uninsured suffer worse outcomes. They may be underrepresented in the registry data (although there are also biological factors in play too). The UK also has a steep inequality curve too, but it is counting everyone so there’s nowhere to hide
    – if we were to count in 100% from Germany, Netherlands and France these countries may well beat out the US (Germany only has 1% in Eurocare!).

    And overall a key point: from what I can see, much of the difference between the US and elsewhere is down to access and use of diagnostics, not treatment. That of course is part of a healthcare system but is also a cultural factor. It’s well known that the Scots, for example, drink and smoke themselves to early graves and avoid doctors but there are superb hospitals in Scotland. So the claims for the overall superiority of American healthcare – if we take into account all the outlying hospitals and the undiagnosed – and not thinking it’s all MD Anderson and Sloan Kettering – may be overinflated.

    This article on Eurocare says of the US:

    ‘European patients need to know that there is no particular reason to think that cancer treatment in the US is better than can be obtained in Europe. It is also important to stress that in both Europe and the US there are large survival differences between the rich and poor. Also, the survival differences between European populations for all cancers combined would decrease after exclusion of prostate cancer, and, to a lesser extent, breast cancer, whose survival is artificially increased by lead time due to screening…’

    http://www.istge.it/fp_acc/index_file/Comparative%20cancer.pdf

    M.

  4. numbersguy
    October 5, 2009 at 10:52 am

    Hi Marc:

    First let me say that I don’t know why your 2nd comment required my approval to be seen, so apologies for the delay in posting it.

    Next, you should note that we’re arguing the same point but merely from different angles. While I believe you are correct in all that you say, my point for this site is to showcase that a deep dive into the facts is not required for understanding, merely a different dive, one with charts and numbers. Specifically some US commentators have cited the Lancet report and merely state that the US is #1 in cancer survival. But until you see the data that supports that (the bar charts here) the reader doesn’t really get a sense of what that means. Assuming the article is true, something that the lay public has to do, the article itself indicates that the US’s lead is not that substantial. When you reflect on this lead in terms of the dollars the US spends on health care, this slim lead hardly seems worth the effort.

    Regarding some of your other points…
    The registry data used in the US did include a breakout in terms of race. And, while there were regional differences, overall the fraction of blacks in the registries was about the US average.

    You should note the original Lancet article included error bars for the various countries. It appears to me that these error bars are the standard statistical thing and do not represent any additional information about the quality of data in the registries. But when the data with the error bars is included it’s easy to see that the US is merely tied for first place with about 4-5 other countries (something I mentioned in my article).

    You correctly point out a feature that I cut out of my original draft of this article. Namely how much of the US ranking here is due to social and cultural features and not directly tied to the health care system? Your example of the Scots drinking and smoking themselves to death and the US possibly having a higher screening rate are things that are not going to change under the proposed bills currently being considered in the US.

    Finally, thanks for the pointers to the additional articles. I am interested in revisiting this topic in a future article and will undoubtedly use the articles you cite when I do so.

  5. Linda
    October 16, 2009 at 9:54 am

    There are many cancers that are slow growing, symptomless and would not kill a person before something else would (many prostrate cancers are of this kind). If, in the US, more of these slow growing cancers are being detected because of the push towards more and more cancer screening, then the five year survival rate would necessary increase but without any actual benefit to the population.

  6. May 17, 2010 at 11:55 pm

    Lung Cancer scared the hell out of me that is why i do not smoke cigarettes anymore.,:~

  7. July 9, 2010 at 9:17 am

    Colon cancer can be avoided if you just keep high fiber foods in your diet.,-*

  8. July 12, 2010 at 9:26 am

    the former president of the philippines Corazon Aquino died also of colon cancer-.:

  9. July 25, 2010 at 10:06 pm

    lung cancer can be avoided if you stay out of air pollutants like some chemicals and tobacco smoke.`;~

  10. August 8, 2010 at 12:12 am

    Whack at using our electronic cigarette as a safer alternative. Smokeless cigarettes are proper increasingly more hot magnitude smokers and promptly to be quitters.

  11. October 23, 2010 at 4:37 pm

    I have enjoyed your viewpoint. My reading has shown your ideas to be true, then again, I have also seen the opposite from different sites like this one. Do you have any ideas for getting more savvy info on natural health or related topics? I would most appreciate it!

  12. Barbara Monroe
    April 5, 2011 at 6:58 pm

    I never smoked; still I have stage 3 lung cancer. I did not have any symptoms other than back pain.

  13. numbersguy
    April 6, 2011 at 1:40 pm

    Hi Barbara:
    Good luck with your cancer. One complaint that I’ve heard about cancer is that it’s categorized merely by where the initial outbreak is. There are apparently many different types of cancers each of which can attack different organs. I suspect (but do not know) lung cancer in non-smokers like yourself may be different from lung cancer in smokers/ex-smokers, yet if true, doctors still refer to both merely as “lung cancer”. Survival rates and other statistics may be more related to this underlying type of cancer than it is with the location of the occurrence.

    Again, good luck to you.

  14. matt
    July 28, 2011 at 4:29 pm

    The assertions of this study, showing the us coming out ahead seem to be contradicted by the OECD study among developed nations from 2000. I’m curious as to the methodology of the people doing the survey showing the survival rate as 90%, what are they doing about people who cannot afford treatment? Are they included? I noticed that these studies that put the US ahead tend to base it off of 5 year + survival rates, so it probably matters what overall cancer mortality is.

    This site (http://cancerdeaths.co/cancer-death-rates-by-country/ ) showing the results of an independent OECD study shows how many cancer patients wind up dying out of the total. A
    If we go by number of overall cancer deaths per 100000, the US comes out at a solid middle among the developed world, but actually well behind Britain and Scandinavia.

    Also, even if we take these studies showing the USA doing awesomely at face value, the blogs claim that just because we deal with cancer better than most nations doesn’t really speak much about any inherent awesomeness in the US system. These blogs tend to ignore the fact that multiple studies have consistently shown the US falling short in other health-related areas such as respiratory disease, infant mortality, and others.

    Any claims on this board or others, attesting to the superiority of the US healthcare system are highly dubious.

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  16. dwayne rhodes
    September 15, 2012 at 5:32 pm

    I am a American Restuarant owner in El Aguacate, Jalisco, MX. married
    to Guadalajara Lady, my problem is my Father-in-law has Lung Cancer, they are NaturalHolistict, they my sister-in-laws are treating him with onion baths, lots of steamed lemon…but nothing else…and here I am world raked Chef…wanting to give food to give him strength, but that is hard when you are dealing with Brujas…..and their faith in God…yet I have the money to take him for treatment , what and how should I proceed…I love my family…and only want the best…I want him to see his grand-kids, we are in Guadalajara finally getting him to see a Organic Doctor, which I do not what that is..any help would be amazing…thank you

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