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Decoding Cancer Everything you've ever wanted to ask about cancer answered on new podcast

As a new Irish podcast aims to demystify the language surrounding cancer, here are the questions and no-nonsense answers host Dr Robert O'Connor says everyone should know.


Dr Robert O’Connor hosts the podcast Decoding Cancer. Picture: Frank McGrath

Dr Robert O’Connor hosts the podcast Decoding Cancer. Picture: Frank McGrath

Dr Robert O’Connor hosts the podcast Decoding Cancer. Picture: Frank McGrath

Podcast Decoding Cancer is back with fascinating episodes on everything from how dogs are helping to sniff out cancer to how immunotherapy works. But first Irish Cancer Society Director of Research Dr Robert O'Connor goes back-to-basics to answer our biggest questions about the disease.

Question: What exactly is cancer?

The first thing is that cancer is not one single disease - it's many different types of diseases with different impacts and outcomes. For example, some common forms of skin cancer, if picked up early, can be very easily treated; conversely, some cancers like pancreatic cancer or ovarian cancer, are much more difficult to treat.

Cancer arises from cells in our own body. Basically, mistakes build up in a cell or group of cells and it makes those cells start to grow abnormally. That growth can then form what we would know as a tumour - a lump of abnormal cells - within our organs and stop them from working properly.

Those mistakes may also make the cells from that tumour start to spread out into the rest of the body. Ultimately, that's what kills people and that's what treatment is designed to try and overcome.


Daffodil Day is the Irish Cancer Society’s biggest awareness campaign each year

Daffodil Day is the Irish Cancer Society’s biggest awareness campaign each year

Daffodil Day is the Irish Cancer Society’s biggest awareness campaign each year

Question: Why do people get cancer?

One of the most common things I hear from people is, 'I eat healthily and exercise and I got cancer'. The first thing is we're all born with a risk of getting cancer. You or I or anybody could be diagnosed at any stage of our life with cancer. Much of what's diagnosed happens spontaneously, so there's no particular explanation for it.

Some people are born with mistakes already in their genes and those mistakes can increase the chances that an abnormal cell will arise, so those would be heritable - or genetic - cancers. Maybe four in 10 cancers have some sort of lifestyle involvement in how they happened.

For instance, we know that most lung cancers originate because of a long smoking history. We also know that there are some good things in our lifestyle that we can do, such as eating a balanced diet and exercise, that can reduce those risks.

Question: Why does cancer spread?

Our cells have a lot of complicated machinery to make sure that a skin cell stays in the skin, a lung cell stays in the lung or a breast cell stays in the breast.

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Cancer spreads because some of the mistakes in the abnormal cells cause more and more mistakes to happen. As those mistakes increase, those mechanisms break down. The cell starts to behave abnormally and starts to eat the tissue around it and spread into the blood and the lymphatic system, where it can start travelling around the body. If it finds an area that has a good blood supply it may sit itself down and produce a new tumour in that area. And that tends to be where we see more cancer spread to areas like the liver, brain and lungs.

Question: What do the different stages mean?

Stage is a broad reflection of how far abnormal the cancer is. So stage one is a cancer which is just resident in that area, and there's no indication that it has spread anywhere else. And that's normally easier to treat and gives a much greater chance of treatment curing the disease. The later stages then reflect a gradual increase in the spread of the cancer.

Stage two would be you're starting to see those cells eat into the surrounding tissue and starting to spread. Stage three would be local spread, and that's normally into the lymph glands, so for example, breast cancer often starts to spread into the lymph glands around the breast, such as the armpit. Stage four is where it has spread to much wider parts of the body, usually multiple organs.

Question: Is stage four cancer always terminal?

It can depend on the cancer. With things like testicular cancer, which tends to be quite sensitive to treatment, even in stage four where it has spread widely, usually it will respond very well to chemotherapy and there's a high chance of cure.

But with most other cancers that later stage means it's much more difficult to treat, because if you think about it, it's spread throughout the body and it's interfering with more organs, so surgery probably isn't going to help much - you've already knocked out one of the ways of treatment. With stage four cancer that effectively means that the cells have spread further, they're having more impact in the body and they're more difficult to treat with medicines.

Question: How does chemotherapy work?

There's a lot of different types of chemotherapy but it's usually medicines that kill actively growing cancer cells. Cancer cells tend to be growing at a faster rate than the cells around them, so they're susceptible to these kinds of medicines that affect cells that are actively growing.

One of the main side effects is that other cells in the body that are actively growing, like the cells in our intestinal system, mouth and hair, can also be affected.

Hence people might lose their hair, they have nausea, diarrhoea, mouth sores - things like that. One of the things people ask me is, 'Why can't I just take a tablet and get rid of the cancer cells?'

The reason is that those cells come from our body so they're almost identical in every way. It's then very difficult to find a medicine that just hits the cancer cell and doesn't hit the rest of our normal cells. And that's where a lot of research is ongoing to try to find medicines that exploit particular very discreet differences in cells.

Question: What's the difference between being in remission and getting the all clear?

For some forms of particularly early stage cancer, we can be very confident that surgery or radiotherapy is likely to work. That will mean that the doctor would be quite confident in talking to the person that all of the tumour has been removed. Unfortunately, in the majority of cases, we may not be fully sure.

Because cells are microscopic, we can't see them; we don't know if perhaps some other cells have escaped from around where treatment has been focused on. Therefore, a doctor will tend to say that the person is in remission.

What remission means is that the cancer doesn't seem to be there or isn't actively growing, so the person is otherwise well, but we don't know and we can't say with certainty that the cancer isn't going to come back. It's quite common for people who've been affected by cancer to worry that the cancer might come back.

It will be rare that a doctor would say to somebody that they're cured. They may give the all clear and say, 'We can't find any evidence of cancer' - and that's a really good milestone for people.

  • Listen to Decoding Cancer on Spotify, Apple Podcasts or at cancer.ie/decoding-cancer-podcast

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