Cancer

What is cancer?

The term 'cancer' includes a large range of malignancies that differ in terms of symptoms, growth rate, treatment options and survival rates. Cancers are tumours or lumps: accumulations of cells formed when a group of cells starts to proliferate uncontrollably and grow due to a failure in the mechanisms that manage cell multiplication. The probability of this happening increases with age, which is why cancer is more common in older people.


A tumour can be benign, in which case it is not (yet) classified as cancer. Further examination is often required and the benign growth may have to be removed. A malignant tumour is described as cancer.


Cancer can occur anywhere in the body. The most common cancers in the general population are: breast cancer, colonic cancer, lung cancer, skin cancer and prostate cancer. Together, these five cancers account for nearly two thirds of all new cancer cases. They are followed by lymph node cancer and leukaemia, bladder cancer, cervical cancer, kidney cancer, stomach cancer, pancreatic cancer, oesophageal cancer, ovarian cancer and cancer in the head and neck area. 74

 

What are the complaints associated with cancer?

Cancer complaints depend on location and growth rate. Signals may include: a lump or swelling somewhere in the body, swollen glands, changes in a birthmark, a new birthmark, persistent cough or hoarseness, coughing up of blood, swallowing problems, permanent changes in bowel movements without obvious cause, prolonged constipation or diarrhoea, unexplained weight loss, skin abnormalities (a scab, wound or ulcer that does not heal), unusual blood loss (such as vaginal blood loss or blood loss between menstrual periods during or after the menopause), secretion from the nipples, blood in the urine not accompanied by pain during urination, persistent abdominal pain, severe recurrent headache, or changes in the size and shape of the testicles.


Of course, the symptoms listed above may indicate conditions that are not cancer. It is sensible to explore further.

 

How common is cancer in the general population?

In the Netherlands in 2014, cancer was the leading cause of mortality in men and women. 456  The risk of people having cancer at any point in their lives is 30%. Over 70% of all new cases of cancer are in people aged over 60.


The estimated prevalence (expressed as the percentage of the population in which cancer has ever been diagnosed and who are still alive at a given date; some of these people will have been cured but the disease will still be present in the others) is 2.5%. The prevalence of breast cancer is highest (approximately a quarter of the total), followed by colonic cancer, lung cancer, skin cancer and prostate cancer. 74

 

How common is cancer in people with intellectual disabilities?

After lung disease, cancer is the second cause of death in people with intellectual disabilities, followed directly by cardiovascular disease. 457  In older studies, cancer was the third cause of death after lung disease and cardiovascular disease. 75


The risk of a person with an intellectual disability ever having cancer is the same as the risk in the general population (30%). However, the incidence rates do vary with age: the risk is higher than in the comparable age groups in the general population for people aged between 15 and 30 years, and lower in people aged over 60. Cancer is equally prevalent in all levels of intellectual disability. 76


The incidence by type of cancer in people with intellectual disabilities differs from the general population. Cancer of the gastrointestinal tract (the stomach and intestines) is most common: Jancar 77  found cancer in the gastrointestinal tract in 58.5% and Cooke 78  found cancer in the gastrointestinal tract in 55% of the total number of cases of cancer.


A major Finnish retrospective study covering a period of thirty years and looking at 2173 people with an intellectual disability found an increased incidence rate for gall bladder cancer (2.8 times more common in people with severe intellectual disability), thyroid cancer (2.1 times higher), oesophageal cancer (twice as high). The same study found a lower incidence rate for prostate cancer (five times less common), cancer in the urinary tract (3.3 times lower) and lung cancer (just as common in mild to moderate intellectual disability but almost twice as low in severe intellectual disability). 79

 

An Australian study of 9049 people with intellectual disabilities found an increased incidence rate for leukaemia (3.3 times more common in men and 4.6 times in women), brain tumours (2.8 times more common in men and 2.3 times in women), stomach cancer (3.3 times more common in men), cervical cancer (3 times more common), colonic cancer (1.4 times more common in men and 3.1 times in women), thyroid cancer (1.7 times more common in men) and testicular cancer (1.4 times more common). This study also found a lower incidence rate for prostate cancer (5 times less common). 76


A study of the records of English GPs showed that cancer was diagnosed less frequently in people with intellectual disabilities than in the general population. 458 This could indicate underdiagnosis. Another English study found that adults with intellectual disabilities actually had poorer health than people in the general population, including an increased prevalence of cancer. 459


People with Down syndrome have a higher risk of leukaemia 460 and testicular cancer.


People with tuberous sclerosis are more likely to have brain tumours and kidney tumours.


Neurofibromatosis is characterised by skin tumours and tumours in the central nervous system.


Brain tumours can be the cause of intellectual disability. 76

30% General population (all cancers)
30% People with intellectual disabilities (all cancers)

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Centraal Bureau voor de Statistiek 2016. http://statline.cbs.nl/

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