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What is cancer?

This blog is the 1st in a series of 5 on the topic of cancer written by Dr Philip Borg MD FRCR FAAMFM.

Dr Borg is a Consultant Cancer Interventional Radiologist and a Longevity Medicine Specialist.

It is hard to think of anyone who has not been affected by cancer either directly or through friends and relatives. Cancer is a dreaded diagnosis and one which is unfortunately increasing in incidence for various reasons.

Worldwide cancer rates are increasing - in 2020 there were 18 million new cases of cancer, and this is projected to increase by 55% by the year 2040. Causes for increase in cancer rates are many. We are living longer and populations worldwide are increasing in size. However even accounting for this, cancer rates are likely increasing because of modifiable lifestyle factors.

38% of cancers are avoidable and are down to smoking, being obese or overweight, drinking alcohol, and having a poor fibre diet. All other lifestyle factors that can cause obesity such as poor fitness, low muscle mass, poor sleep, stress and poor metabolic health are also risk factors.

Cancer is a disease in which some of the body’s cells grow uncontrollably and may spread to other parts of the body. Cancer can start almost anywhere in the human body and because cancer can grow in different organs and from different cell types, one can think of cancer as a set of diseases which can behave differently.

The human body is made up of trillions of cells which grow and multiply to form new cells. This growth is highly regulated and when cells have multiplied a number of times or when they become damaged, they are removed and replaced.

This highly regulated process may sometimes become dysregulated and abnormal cells grow and multiply uncontrollably. Sometimes the body recognises these rogue cells and removes them. Other times these cells can multiply to form tumours, which may be cancerous or benign.

A primary tumour is the site or organ where a cancer has started to grow uncontrollably. Cancer can sometimes spread to other parts of the body and become a metastasis or secondary tumour. This may occur either by the cancerous cells invading nearby tissues or by travelling via the blood or lymphatic system. When cancer travels it can form new tumours distant to the primary tumour and these are called metastases. Except with brain tumours that occur in a closed space (the skull), the primary tumour is not usually the cause of death in cancer patients. Death happens because of metastatic cancer cells travelling to, and growing in, and eventually replacing most of the normal cells a vital organ such as the liver, lung or brain.

Tumours can also be divided into solid tumours (for example lung, colon, breast and prostate) and blood tumours such as leukemias. Benign tumours do not invade other tissues and do not metastasise, however may cause symptoms due to local effects like pressure caused by increase in size.

Cancer cells differ from normal cells in a number of distinctive ways. The following are some of the most significant differences:

  1. Cancer cells grow and divide uncontrollably, whereas normal cells grow and divide in a controlled way;

  2. Cancer cells remain immature and undifferentiated as they divide quickly;

  3. Normal cells undergo apoptosis (programmed death) once it is old or damaged. Cancerous cells do not repair themselves or undergo apoptosis;

  4. Some cancer cells have the ability to invade different parts of the body, normal cells cannot;

  5. Damaged and abnormal cells are normally eliminated by the body’s immune system. Cancer cells have the ability to evade this process and sometimes even ‘convince’ the immune system to protect the tumour.

These distinct characteristics of cancer cells are taken advantage of by researchers when developing targeted therapies to combat cancer. Targeted therapies stop cancer from growing and spreading with little to no effect on normal cells.

These unique characteristics of cancerous cells are also employed for cancer screening purposes. The lack of apoptosis displayed by cancerous cells, is for example, used in an innovative cancer screening technology - Trucheck Intelli ™.

The commonest cancers worldwide are lung and bronchus, bowel cancer, stomach, breast and pancreatic cancer (the incidence and commonest cancers varies in different countries). In 2020 more than 40% of new cases of cancer are lung, female breast, bowel or prostate cancer.

The 5 year survival rates (the number of people that are alive 5 years after a cancer diagnosis) also varies widely in different cancers. For example the 5 year survival rate for testicular cancer is 98% compared to just 1% for pancreatic cancer.

Cancers are diagnosed at different stages (how big and how far they have spread). All cancers have a better prognosis when diagnosed at an earlier stage, hence the importance of cancer screening.

An example of the difference in survival rates of bowel cancer according to stage

The importance of cancer prevention, screening, early symptoms and cancer treatment will be discussed in future blogs in this 5 part cancer series.

For more information about the longevitydoctor cancer screening service please visit


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