What is cancer? Part I

Hi, I'm Richard Bell. I'm a cancer clinician - I care for patients with cancer in my daily life and my task today is to talk to you about what cancer is, and what are clinical trials in cancer.

Fundamental to an understanding of cancer - which is all about distorted cell growth, is an understanding of how cells grow. If you look at this little animated sequence you'll see that here are some cells and here are the nuclei of the cells.

Before they divide, the first thing that happens in the nucleus divides, and I'll activate this now. And if you watch you'll see the cells round up, divide the nucleus and then there are more cells. So this is cell replication.

But how do we end up with 2 cells that contain all of the genetic information - all of the DNA, all of the knowledge of how a cell exists?

In that process it's not as chaotic or as random as you might think. The first thing that happens in the DNA - the chromosomes become a soup. They are separated. And you can see that this is a bit of a mess. How can you end up with a complete set of every gene, of every chromosome in each of the daughter cells?

Well the body has a process and it's called the spindle. It organises the chromosomes after they've been reduplicated and then in a process, it pulls those chromosomes apart so now you can see here that there's two sets of chromosomes for the two daughter cells.

This process is called mitosis and these are some of the targets that we're able to attack when we're treating cancer.

So what exactly is cancer?

It's an altered population of cells. Remember the cells I showed you, which have the ability to grow in an unrestrained manor. The second part of the definition is the ability to spread locally, which is called invasion, and to distant sites, which is known as a process of metastasis.

So the key attributes, the things to hold in your head, are uncontrolled growth and the ability to spread locally and to distant sites. They are the key attributes of cancer.

This, is a pretty shocking picture. This lady, Gwen, was 92 and living in a granny flat and she did not wish to be a burden to her children. So she kept her own counsel about what was happening to her right breast. This is a large malignant ulcer.

I'll show you with the pointer, all of this is cancer. This is a large lump of malignant lymph glands in the armpit. Here is cancer actually growing out of the breast tissue where the nipple used to be.

So this is growth, you can see growing cells en masse here. This is uncontrolled growth and you can see invasion going on.

This now is showing metastases. These are in fact CT scans of a different lady, and here in the liver you can see there are lots of spots. Each one of these spots is in fact cancer that has spread to the liver. On the right you can see a mass which is in the lung. The lung in this image is dark because it's full of air so the lung appears to be dark, and you can also see there's a big puddle of fluid on this side of the chest.

So this is metastatic breast cancer. And it is typical of the pattern of spread that you see in this particular disease.

Here's an Xray of the hip. And what you can see is a bullet hole. Something has munched the bone in this position here. And this again has been caused by cancer spreading. It began with breast cancer - I'm using that as an example - to the femur, to the hip bone.

If you could look inside the bone, it would look something like this. The red marrow is the stuff that makes our blood cells. And here you can see the abnormal tumor cells in collection, so here are the tumors within the marrow.

So this once again fits with our definition. This is cancer spreading to other sites. This is the metastatic potential of cancer. It got there via the blood stream.

This will look bewildering to you, but what is abnormal here is some of these red cells are a bit purple looking and a bit plump. This patient is anaemic - there aren't enough of the red cells. So we went looking to find out what was going on here. She hadn't apparently bled, she wasn't short of iron, there wasn't a common cause for anaemia. And we knew that she had breast cancer.

This little panel that's just appeared shows her bone marrow. The good guys are seen here in the top right hand corner - these small cells are the normal bone marrow cells. These bigger, uglier and irregular cells are in fact breast cancer that's spread to her bone marrow and are the direct cause of the abnormalities in the blood cells that are seen in the blood film.

We can prove it. Here we've stained for keratin. Bone marrow cells don't produce keratin. Breast cancer cells do. Here's proof positive that these bad guys are not native to the bone marrow, they haven't arisen in the bone marrow, they've come from somewhere else.

Breast cancer cells often contain receptors for hormones. In this case they did not. There's no brown staining. But looking for another receptor, the HER-2 receptor, you see very, very strong staining here.

So how do we make sense of all of this? We go through some steps that, although they seem complex, consist of asking some quite simple questions.

Doctors talk in very specific ways and that can be quite bewildering for patients and to their families. When we talk about a prognosis, we're talking about what does the future hold.

When we use the word ‘prediction' we use it in a very narrow sense. We use it to predict what treatment is most likely to work and also what treatments are not worth trying because they aren't likely to work. So if your doctor talks about prediction in this context, it's a very narrow use of the word prediction.

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