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Cancer survival rates ...

Posted Mar 28 2009 3:51pm

Cancer survival rates

Cancer survival has improved overall in countries across Europe

29 mar 2009--Widespread media coverage has been given to a large study on cancer survival across Europe. The EUROCARE-4 study looked at cancer cure and survival rates between 1995 and 2004. The Guardian reported that although the number of people being cured of cancer is steadily climbing across Europe, cure rates in England and Scotland trail those in many other countries. The Daily Mail reported that “cancer survival rates in Britain [are] among the worst in Europe".

This important study analysed a vast amount of data on cancer survival in Europe. Although the newspapers and the study have given possible explanations for the variations in cancer survival between countries, the study did not examine this in detail. Various factors could have been involved, including differences in cancer prevention and detection strategies, diagnostic rates, cancer stage at diagnosis, how cancers are classified, what proportion of cancers are recorded in the cancer registries, and what treatments were given.

Further study would be needed to determine the contribution of each of these factors and how to improve survival rates.

Additionally, these figures are for cancers diagnosed more than 10 years ago, and survival rates may have improved since then.

Where did the story come from?

This research was carried out by the EUROCARE-4 study group, comprised of researchers from across Europe. The study was funded by the Compagnia di San Paolo foundation in Italy. Nine articles and an editorial about the EUROCARE-4 were published in a special edition of the peer-reviewed European Journal of Cancer. Much like the majority of the media interest, this analysis focuses on the results for five-year survival from cancer.

What kind of scientific study was this?

This registry-based cohort study, called the EUROCARE study, looked at cure and survival rates of people diagnosed with cancer in Europe. The EUROCARE study began in 1990, and papers have already been published on survival rates for people diagnosed with cancer between 1978 and 1985, 1985 and 1989, and 1990 to 1994 (EUROCARE studies one to three).

For the current study (EUROCARE-4) the researchers obtained data from 93 cancer registries in 23 countries. Thirteen of the countries, including the UK, had national cancer registries, where all cancer cases are recorded. The coverage of the registries varied among the other countries, with between 8% to 58% of their populations covered. Germany has national cancer coverage for children, but only 1.3% of adults are covered. Overall, the data covered an average of about 151,400,000 members of the population (not just those who developed cancer) from 1995 to 1999, which is about 35% of the total population of these countries.

To participate in EUROCARE-4, the registries were required to collect a standard set of data for each cancer case. This included the person’s age, gender, date of birth, diagnosis, type and location of cancer, and other cancer characteristics. The data also included which cancer came first (if they were diagnosed with multiple primary cancers), whether the person was alive or dead, and when their survival status was last checked up.

Because different cancer registries had different ways of determining the first primary tumour in people with multiple cancers, the researchers standardised this information using data from the registries and their own system. Information on the cancer stage at diagnosis was collected by some cancer registries, but not all.

The researchers looked at cancer survival rates for people diagnosed with cancer between 1995 and 1999, but also looked at survival in cases diagnosed from 1978 to 2002 using data they had collected in all the EUROCARE studies. In all, the registries contained 13,814,573 cases of cancer diagnosed between 1978 and 2002, the majority of which were malignant (92%).

Cancer site and characteristics were classified according to an internationally accepted system. Records were checked for consistency in various ways, and those that were suspected to be incorrect were returned to the registries for correction. Only a person’s first malignant cancer diagnosis was used in the analyses. Cases of cancer identified from death certificates or discovered at autopsy were excluded from the analyses.

As well as overall age-adjusted analyses, separate analyses were carried out according to year of diagnosis, registry, gender, age, and cancer site. Of the 5,753,934 malignant adult cancers used in the survival analysis, 90% had been confirmed by microscopic analysis of tumour tissue.

The paper on overall five-year survival described the results of the analysis of about 3m adult cancer cases that were diagnosed between 1995 and 1999 and followed until the end of 2003. Data on some cancer sites was missing from the Danish data, and as this could affect overall survival estimates, Denmark was excluded from these overall analyses. Survival among people with cancer relative to the expected survival of people from the general population of the same age and gender, was calculated at one and five years after diagnosis.

This method of comparing observed survival with expected survival is often used in registry studies to compare survival across countries that have different rates of non-cancer deaths (e.g. from heart disease, etc.).

The researchers also looked at the likelihood of surviving to five years if a person survived for one year after diagnosis, and compared this with overall five-year survival.

What were the results of the study?

Across the European countries studied, people diagnosed with any cancer between 1995 and 1999 had a five-year survival rate (adjusted for age) that was half that of the general population. This was an increase on the previous study, which found a 47% survival rate for cancers diagnosed between 1990 and 1994.

For individual countries, five-year relative survival was highest in Sweden (58%) and lowest in Poland (39%). In the UK and Ireland, relative survival ranged from 43-48%.

The researchers noted that the differences in cancer survival between countries, as identified in previous EUROCARE studies, have narrowed. They say that bladder cancer, prostate cancer, and chronic myeloid leukaemia showed the greatest difference in five-year relative survival between countries in this latest study.

In general, relative five-year survival from all cancers except the blood cancers (e.g. leukaemias) was highest in northern Europe (Finland, Sweden, Norway, and Iceland), “considerably” lower in Denmark and the UK, and lowest in eastern Europe (Slovenia, Poland, and the Czech Republic).

Within the UK, there was little variation in survival in most types of cancer across the 12 cancer registries from different regions.

Relative survival decreased with increasing age at diagnosis. The greatest difference between the youngest and oldest age groups in absolute five-year survival was about 40-50% for cancers of the cervix, ovary, brain and thyroid, Hodgkin’s disease and multiple myeloma. For cancers of the vagina and vulva, testis, bladder and kidney, as well as for non-Hodgkin’s lymphoma and chronic myeloid leukaemia, the difference was 31-39%. Women had better survival than men for most cancer sites, except for bladder and biliary tract cancer.

When the researchers looked at five-year survival for those who were still alive one year after diagnosis (conditional survival), this varied less between countries compared with overall five-year survival. This is because many people with advanced cancer die in the year after diagnosis, and those who survive past one year have similar cancer stages. The difference between conditional and overall five-year relative survival was largest for stomach cancer, kidney cancer, non-Hodgkin’s lymphoma, ovarian and colorectal cancer. These differences were largest in countries with low survival rates.

What interpretations did the researchers draw from these results?

The researchers concluded that the EUROCARE study “continues to provide important indications as to the relative efficiency of national health systems in caring for their cancer patients”. They say that their study “has highlighted marked differences in cancer survival across Europe”, but that “these survival differences have narrowed considerably since EUROCARE began, suggesting that inequalities in cancer care across Europe are also narrowing”.

This important study has analysed a vast amount of data on cancer survival across Europe, and it will be of great interest to health services and cancer researchers. There are a number of points to note:

  • Although the study and several newspapers have given possible explanations for why cancer survival varies across Europe, the study did not look into this in detail. Various factors could have been involved, including differences between countries in disease prevention and detection strategies, diagnostic rates (under- or over-diagnosis), cancer stage at diagnosis, how cancers are classified, what proportion of cancers are recorded in the cancer registries, and treatments that are given. Further in-depth analysis would be needed to untangle the effects of these contributing factors, and to determine how survival figures could be improved.
  • The accuracy of the figures depends on the accuracy and completeness of the recording in the original registries. Although the researchers took steps to ensure the quality of the data and took into account the coverage of the registries, these factors may still have had an effect.
  • The main analyses was of cancers diagnosed between 1995 and 1999. Survival rates for cancers diagnosed since 1999 may be different due to changes in how cancers are diagnosed and treated.
  • Although the Daily Mail reports that survival for five years or more after diagnosis in the UK is down from previous figures of 42% in men and 53% in women to 41.4% in men and 51.4% in women, it is unclear exactly which of the many Eurocare publications these previous figures come from. Figures from one of the current EUROCARE-4 publications looking at survival trends between 1988 and 1999 suggest that five-year survival among cancer patients in the UK (relative to the general population) increased over this period.

The EUROCARE study also offered the good news that cancer survival rates in Europe have improved, and the difference in survival between countries is reducing. The information provided from this and other studies will help to identify areas that could be further improved.

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