A breast cancer cell Credit: London Research Institute EM Unit
Our Science Surgery series answers your cancer science questions.
If you have a question that you’d like us to answer, send it to us using the email address at the bottom of this post.
Tommy asked: “Does having had one type of cancer (and cured) make you more susceptible to getting any other type?”
To begin answering this question, you have to know the difference between second cancers, which this relates to, and secondary cancers. Second cancers are those that develop after a person has already had one cancer, and the two diseases are unrelated. Secondary cancers are where a person’s cancer comes back or spreads to another part of the body.
Now that more people are surviving cancer, scientists can follow more patients after they’ve been treated and record their health over time. And this includes seeing if they develop second cancers.
It’s this research that’s answering Tommy’s question. And it seems that the basic answer is ‘yes’, but the risk of developing a second cancer is very small. It also depends on many factors, which we’ll now explore in more detail.
One of the main culprits behind the risk of a second cancer is the type of treatment a patient had for their first, or primary cancer.
Certain chemotherapy drugs work by fatally damaging the DNA of fast-growing cells, a characteristic of cancer cells. But these drugs can also inadvertently affect healthy cells that are naturally dividing in the body, such as those in the blood.
This is what causes treatment side effects. And if the damaged cells don’t die, it’s possible this damage could lead to these cells becoming cancerous. That’s why some chemotherapy drugs have been linked with leukaemia, a type of blood cancer.
Radiotherapy also works by inflicting deadly damage to the DNA of cancer cells. While this has become a very precise, sophisticated treatment over the years, the radiation can still damage healthy cells around the tumour, which could increase the likelihood they one day become cancerous.
The risk from radiotherapy also depends on the amount of radiation given, and where in the body. For example breast cancer patients may have a higher risk of developing lung cancer, as the lungs are near the breast tissue.
To get a good look at what’s going on inside a person – whether that’s to help diagnose cancer, or monitor a cancer they’ve already been diagnosed with – doctors can use a variety of imaging techniques. Some of these, like x-rays and CT scans, use radiation to create pictures of the body’s inner workings.
These types of scans carry a very small risk of damaging healthy cells which, similar to radiotherapy, depends on how much radiation a person has received. But they’re an important part of some people’s cancer diagnosis and treatment, which is why the benefits outweigh the small potential risks when these scans are necessary.
The factors discussed so far relate to a person’s first cancer. But there are also many other factors that can raise the risk of a second cancer that aren’t related in this way. These include:
- Genetics: Some people inherit faults in genes that raise their risk of developing a number of different cancers, such as the BRCA1 or BRCA2 genes. So it’s possible that people whose cells carry these faults could develop second cancer as a result of their genes, following treatment and recovery from another cancer caused by the same underlying genetics.
- Lifestyle and environment: Certain things that fall under these categories, like smoking, can cause many different cancers. This means that if a person develops one type of cancer because of smoking, such as bladder cancer, it’s possible that the harm from smoking could lead to another later, like lung cancer.
- Age: Ageing is the biggest risk factor for most cancers. As many of us are living longer, the cells in our bodies have more time to go awry as they build up years of wear and tear. So if a person develops cancer when they’re young, unfortunately they’ll have a greater risk of developing a second cancer than someone who was diagnosed late in life, simply because they’ll be alive for longer after treatment.
The key difference between these risk factors and others is that the risk of a second cancer is tied to the person’s already heightened risk of developing cancer throughout their life, rather than being linked to their primary cancer.
So what does all of this mean?
This question can’t be answered with a simple ‘yes’ or ‘no’.
“We’ve known for decades that certain treatments carry risk of developing cancer,” says Professor Anthony Moorman, a Cancer Research UK-funded scientist working to improve the outlook for blood cancer patients.
“That’s why treatment schedules are constantly reviewed and, wherever possible, the intensity of the drugs is reduced in order to minimise the risk of second cancer but without reducing the chance of curing the primary cancer.”
“Ultimately, not taking cancer treatment is going to open up so many more problems than the small risk of developing a second cancer”
– Professor Moorman
“We need to continue and expand research into the long-term effects of cancer therapy because, fortunately, more and more people, especially children, are being cured of their primary cancer and we want them to go on and enjoy long healthy lives.”
Moorman says that while second cancers have been recognised for some time, the risk is still very small. A recent study carried out in Denmark found that the risk of cancer developing in people who have had cancer before was only 1.1 times greater than people who have no history of cancer.
“Ultimately, not taking cancer treatment is going to open up so many more problems than the small risk of developing a second cancer,” says Moorman. “Taking the recommended treatment is the patients’ very best chance of surviving.”
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