Cancer is not contagious

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Some patients fear spreading the disease, but cancer cells cannot trick another body's immune system

A patient asked me: "Will I spread it to my family?"

 

Given the attention the coronavirus pandemic has attracted of late, you would likely think I was attending to a Covid-19 patient.

 

I was not. The question came from a woman in her 50s who was recently diagnosed with advanced lung cancer.

 

You might think this question is silly. Is it not common knowledge that cancer is not contagious?

 

In truth, every so often, a patient or his or her family will raise this concern with me during our consultation.

 

While most patients would have heard of this fact at one point or another, niggling doubts somehow persist in their minds.

 

This is especially true of patients with advanced cancers that have spread widely through their bodies.

 

They often reason that, since the cancer cells have the ability to spread rapidly from one part of the body to another, there must be at least a remote chance that these cells may spread to another person in certain circumstances such as situations of intimate contact.

 

After learning that cancer cells spread from one part of their bodies to another through the blood, patients often infer that their blood is "contaminated" and if anyone else accidentally comes into contact with their blood, this hapless person may contract cancer.

 

So, why does it not happen? Simply put, this is because cancer cells can fool the immune system of the patient's body, but not the immune system of another body.

 

Cancer cells are normal cells that have mutated and picked up frightening abilities to rapidly multiply and invade different parts of the body.

 

These cells are normal cells that have gone rogue. Their mutated appearances, in molecular terms, are somewhat different from normal cells.

 

Cancer cells carry certain abnormal proteins, known as antigens, on their surfaces. The immune system can potentially recognise such differences and attack the abnormal cancer cells.

 

Cancer cells, however, develop the ability to camouflage such differences - thus avoiding the onslaught of the immune system - and survive.

 

To survive in a body other than their body of origin, cancer cells would have to develop camouflage skills of a totally different order. Thankfully, this is way beyond their ken.

 

The differences between cancer and normal cells in the body of origin are subtle. After all, both mutated cancer cells and normal cells originate from the same mother cell.

 

Most of the proteins on the surface of these cancer cells, which give them their molecular signature, are also similar to those of normal cells.

 

While they are different, cancer cells, when mingling among the normal cells of the body, are akin to folks of the same race speaking the same language, but perhaps with a slightly different accent. This accent can be concealed.

 

The current strategy of using the immune system to attack cancer, known as immunotherapy, hinges on coaxing the immune system to recognise the subtle differences between cancer and normal cells.

 

Should cancer cells from one body manage to gain entry into another body, they would be akin to foreigners with a totally different skin tone and hair colour, speaking in a foreign tongue.

 

Cancer cells' surface antigens would be altogether different from those of normal cells in another body, as the two groups originate from different bodies. Concealment from the other body's immune system would be all but impossible and these cancer cells would face certain destruction.

 

While cancer cells cannot spread from person to person, cancer-causing genes can be passed from one generation to the next. Infective agents that trigger cancer formation may also be passed from one person to the next.

 

For instance, the gene BRCA, which is associated with breast and ovary cancers, made headlines when Hollywood star Angelina Jolie was revealed to have inherited this gene from her mother, and decided to undergo pre-emptive surgery to remove her breasts and ovaries.

 

Singapore started the mass vaccination of secondary-school girls against the human papillomavirus (HPV) in April last year. HPV infection is strongly associated with the subsequent development of cervical cancer.

 

However, the passing of hereditary cancer-causing genes or cancer-causing infections should not be confused with the spread of cancer cells.

 

This bears repeating: The spread of cancer cells from one person to another is categorically impossible.

 

Giving the scientific rationale for this will hopefully put this myth to rest in people's minds.

 

Returning to the topic of Covid-19 infection, cancer patients undergoing treatment do have to take precautions. They belong to a vulnerable group of people who are at greater risk of developing severe complications, should they pick up the bug.

 

Do remember to stay away from crowds and wash your hands often.

 

Dr Wong Seng Weng is the medical director and consultant medical oncologist at The Cancer Centre.

Source: The Straits Times © Singapore Press Holdings Limited. Reproduced with permission.
 

 

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