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What is cancer prevalence and where is the data from?

We use the term 'cancer prevalence' for the number of people who have been diagnosed with cancer in the past, and who are still alive on a given date. The date used for prevalence throughout the LCI Wales tool is 31 December 2015. We present 21-year prevalence, which is the number of people still alive on 31 December 2015, who were registered with a cancer diagnosis within the 21-year period from 1995-2015.

The cancers included are highlighted in the general FAQs section, 'What cancer types are included?'

Cancer prevalence figures have been calculated by counting the number of people diagnosed with cancer in the given period, based on the information collected by WCISU (Welsh Cancer Intelligence and Surveillance Unit).

The 'All cancers combined' prevalence is based on the first cancer diagnosis of any type. The cancer-specific prevalence is based on the first diagnosis of each specific cancer – for example, if a person was diagnosed with lung cancer in 1999 and colorectal cancer in 2005, they would be included in counts for both lung and colorectal cancers. If that person was diagnosed with breast cancer in 1999 then with breast cancer again in 2000, that person would be counted only once in breast cancer, based on their first breast cancer diagnosis in 1999.

The numbers in this analysis may not agree with those published elsewhere due to differences in methodologies, periods of observation, data sets and rounding. It uses data sourced and presented in collaboration with the Welsh Cancer Intelligence and Surveillance Unit, Health Intelligence Division, Public Health Wales, the Scottish Cancer Registry and the Northern Ireland Cancer Registry which is funded by the Public Health Agency for Northern Ireland.

The data has been sourced by WCISU, which has calculated the prevalence based on their database of cancer patients in Wales.

Welsh Cancer Intelligence and Surveillance Unit (WCISU). Data extract. 2018.

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Why is prevalence important?

Cancer prevalence statistics are essential in understanding the number of people who have previously received a diagnosis of cancer and to start to indicate their needs for care. For some of these people, the cancer will be influencing most aspects of their lives, while for others the impact will be less acute.

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Why is time since diagnosis important?

The cancer prevalence data are provided for the total 21-year period. This shows how many people have recently been diagnosed with cancer, and how many are longer term survivors.

The prevalence figures for the 21-year period is a useful indicator of the impact of cancer as a whole, however, patient needs and experiences will vary over time after diagnosis.

Segmenting the cancer population by time since diagnosis can therefore help to inform health care service planning, for the needs of people living with and beyond cancer at different time periods on their pathway.

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Why is prevalence rising?

The increase in prevalence is a function of the growing and ageing population, alongside the increasing number of people being diagnosed with and surviving cancer.

The growth in cancer incidence and survival is due to the following main factors:

  • An ageing population: life expectancy is increasing, with more elderly people alive today than ever before. Cancer is primarily a disease of older people, so there are more people being diagnosed with cancer.
  • A greater focus on early diagnosis.
  • Advances in cancer treatments.
  • Changing lifestyle risk factors: for example, increases in obesity rates.

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How have future prevalence estimates been calculated?

Our future prevalence estimates are the number of people who might be living with cancer up to 21 years after being diagnosed. So, for example, the 21-year prevalence rate in 2030 is our estimate of the number of people who will be living with cancer who have been diagnosed between 2010 and 2030.

Sources:
Welsh Cancer Intelligence and Surveillance Unit (WCISU). Data extract. 2018.

Maddams J, Utley M, Møller H. 2012. Projections of cancer prevalence in the United Kingdom, 2010-2040. Br J Cancer 2012; 107: 1195-1202.

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How accurately can you predict future prevalence?

Predicting future prevalence is difficult. The future prevalence estimates provided here are based on crude calculations and provide proxy numbers. Future estimates will naturally change over time, as more data and analysis become available.

We provide these estimates to give an indication of how your local population might grow, reflecting two possible future scenarios.

However, there are some limitations and a number of assumptions involved in predicting future trends. We have noted these key points below.   

Our Health Board and Local Authority estimates are based on:

Applying UK-wide projections of prevalence to the WCISU Health Board and Local Authority areas 21-year prevalence figures for 2015. So we are assuming the rate of change in the UK will be the same for each area in Wales. For example, if a population ages or grows faster than the UK overall, or if it is more or less socioeconomically deprived compared to the rest of the UK, the future estimate for that area will not reflect such differences.

Methods which do not take into account unknown factors that may happen in the future, for example factors that influence cancer incidence (like smoking rates, screening programmes or risky lifestyles) or outcomes (such as new treatments or changes in access to care).

Where people lived at the time of their diagnosis, not where they live now or in the future – so the future estimates do not take into account population movement since time of diagnosis or in the future.

Projections of future prevalence are therefore indicative only, but they provide some estimate of the number of people living with cancer for all Wales combined and each Health Board or Local Authority area in both the short- and long-term. So, despite these caveats, these data can be used to influence planning as it is clear that the cancer population is going to increase.

Sources:

Welsh Cancer Intelligence and Surveillance Unit (WCISU). Data extract. 2018.

Maddams J, Utley M, Møller H. 2012. Projections of cancer prevalence in the United Kingdom, 2010-2040. Br J Cancer 2012; 107: 1195-1202.

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