Cancer Incidence, Survival and Mortality Data

Cancer is not one single disease but describes a process that begins with a series of cell changes.  There are more than 200 different types of cancer.  In Ireland, the most common types of cancer are prostate, colorectal and lung cancers for males, and breast, colorectal and lung cancers for females.

We monitor the incidence, mortality and survival patterns of cancer in Ireland using data and reports from the National Cancer Registry, Ireland as well as statistics from the Central Statistics Office and the Public Health Information System.  These data also gives us information on trends over time, place (by HSE area or county) and person (by age group or sex).

n/a means "not applicable" 

Rate means the number of cases per 100,000 population per year (European Age Standardised).  

Source: NCRI Database, accessed 10^th December 2013

n/a means "not applicable".  

Rate means the number of cases per 100,000 population per year (European Age Standardised).

Source: NCRI “Cancer in Ireland 2013” report

Incidence, survival and mortality

The three most common groups of statistics produced about cancer include incidence,survival andmortality statistics.  They mean very different things.  

What do incidence statistics mean?

Incidence of cancer is the number of people who get a particular type of cancer in a defined time period (usually a year). It is often written as number of cancer cases per 100,000 people in the general population. These calculations are done for every type of cancer. 

For example, in Ireland in 2010, there were 

1,029 women diagnosed with colorectal cancer - about 45 cases per 100,000 women

3,230  men diagnosed with prostate cancer - about 143 cases per 100,000 men

1,307 men diagnosed with lung cancer - about 58 cases per 100,000 men

A particular type of incidence statistics is known as an age standardised incidence rate.

Because cancer is more common in older populations, when comparing different populations, it is important to ensure that the population age structures are the same.  Otherwise spurious differences will be discovered which are actually due to the different age structures in the population and not due to actual differences in the incidence of cancer between the populations.  This is done using a statistical method known as age standardisation.  You may sometimes see incidence rates described as ASR (age standardisd rate) or EASR (European age standardised rate).  These terms mean that the rate has been adjusted to allow for the differences in the age structure of the populations being examined.     

Cancer incidence rates rarely differ from year to year, though significant changes in rates can be seen over a longer time period, e.g. decade.

Relative survival rate

Relative survival rates for cancer are usually written as '5 year survival' or '10 year survival'.

Relative cancer survival rate is a number that estimates the chance of a person with a particular type of cancer surviving a particular time period, usually 5 or 10 years.  It compares the proportion of people with a particular type of cancer who are still alive after 5 or 10 years compared to a group of people who are cancer free and is an estimate of the amount that a specific type of cancer shortens life.  For example, a 5-year relative survival estimate of 80% for breast cancer means that 80% of the people with breast cancer who were expected to be alive 5 years after the diagnosis, given their age and sex, were in fact still alive.  

5 and 10 year survival statistics

5 year and 10 year time periods are used largely for convenience. Research studies often follow people up for 5 or 10 years. So figures for 5 and 10 years are often available to be quoted.

Survival statistics refer to the whole population of people who were diagnosed with cancer or a subtype of cancer in a particular year.  Survival statistics may vary depending on the age and sex of the patient as well as the type, stage and grade of the cancer.  So, although the statistics quoted are true for the population they describe, they may not apply to you as an individual.

Improved survival rates are a sign that developments in treatments and screening techniques for cancer are working.

Survival

Source: NCRI Database – accessed online 10^th December 2013

Mortality statistics

Mortality statistics mean the number of people who have died from a particular type of cancer in a year. On their own, these figures don't mean much. They have to be looked at alongside incidence figures and other statistics.

You may read that in 2009, there were 2,351 people diagnosed with colorectal cancer and that same year, 945 people died of colorectal cancer.  The people who died are unlikely to be the same people that were diagnosed in 2009.  Most of the people who died in 2009 would have been diagnosed in earlier years.

As with incidence statistics, mortality statistics are general.  They don't take account of stage, grade or any specific sub type of a cancer. They are used as a general guide to what is happening in diagnosis and treatment of diseases.

For more information, visit the National Cancer Registry's website, www.ncri.ie.