Catherine, Princess of Wales, has announced she has now completed a course of preventive chemotherapy.

The news comes nine months after the princess first revealed she was being treated for an unspecified form of cancer.

In the new video message released by Kensington Palace, Princess Catherine says she’s focused on doing what she can to stay “cancer-free”. She acknowledges her cancer journey is not over and the “path to recovery and healing is long”.

While we don’t know the details of the princess’s cancer or treatment, it raises some questions about how we declare someone fully clear of the disease. So what does being – and staying – “cancer-free” mean?

What’s the difference between being cancer-free and in remission?

Medically, “cancer-free” means two things. First, it means no cancer cells are able to be detected in a patient’s body using the available testing methods. Second, there is no cancer left in the patient.

These might sound basically the same. But this second aspect of “cancer-free” can be complicated, as it’s essentially impossible to be sure no cancer cells have survived a treatment.

It only takes a few surviving cells for the cancer to grow back. But these cells may not be detectable via testing, and can lie dormant for some time. The possibility of some cells still surviving means it is more accurate to say a patient is “in remission”, rather than “cancer-free”.

Remission means there is no detectable cancer left. Once a patient has been in remission for a certain period of time, they are often considered to be fully “cancer-free”.

Princess Catherine was not necessarily speaking in the strict medical sense. Nonetheless, she is clearly signalling a promising step in her recovery.

What happens during remission?

During remission, patients will usually undergo surveillance testing to make sure their cancer hasn’t returned. Detection tests can vary greatly depending on both the patient and their cancer type.

Many tests involve simply looking at different organs to see if there are cancer cells present, but at varying levels of complexity.

Some cancers can be detected with the naked eye, such as skin cancers. In other cases, technology is needed: colonoscopies for colorectal cancers, X-ray mammograms for breast cancers, or CT scans for lung cancers. There are also molecular tests, which test for the presence of cancer cells using protein or DNA from blood or tissue samples.

For most patients, testing will continue for years at regular intervals. Surveillance testing ensures any returning cancer is caught early, giving patients the best chance of successful treatment.

Remaining in remission for five years can be a huge milestone in a patient’s cancer journey. For most types of cancer, the chances of cancer returning drop significantly after five years of remission. After this point, surveillance testing may be performed less frequently, as the patients might be deemed to be at a lower risk of their cancer returning.

Measuring survival rates

Because it is very difficult to tell when a cancer is “cured”, clinicians may instead refer to a “five-year survival rate”. This measures how likely a cancer patient is to be alive five years after their diagnosis.

For example, data shows the five-year survival rate for bowel cancer among Australian women (of all ages) is around 70%. That means if you had 100 patients with bowel cancer, after five years you would expect 70 to still be alive and 30 to have succumbed to the disease.

These statistics can’t tell us much about individual cases. But comparing five-year survival rates between large groups of patients after different cancer treatments can help clinicians make the often complex decisions about how best to treat their patients.

The likelihood of cancer coming back, or recurring, is influenced by many factors which can vary over time. For instance, approximately 30% of people with lung cancer develop a recurrent disease, even after treatment. On the other hand, breast cancer recurrence within two years of the initial diagnosis is approximately 15%. Within five years it drops to 10%. After ten, it falls below 2%.

These are generalisations though – recurrence rates can vary greatly depending on things such as what kind of cancer the patient has, how advanced it is, and whether it has spread.

Staying cancer-free

Princess Catherine says her focus now is to “stay cancer-free”. What might this involve?

How a cancer develops and whether it recurs can be influenced by things we can’t control, such as age, ethnicity, gender, genetics and hormones.

However, there are sometimes environmental factors we can control. That includes things like exposure to UV radiation from the sun, or inhaling carcinogens like tobacco.

Lifestyle factors also play a role. Poor diet and nutrition, a lack of exercise and excessive alcohol consumption can all contribute to cancer development.

Research estimates more than half of all cancers could potentially be prevented through regular screening and maintaining a healthy lifestyle (not to mention preventing other chronic conditions such as heart disease and diabetes).

Recommendations to reduce cancer risk are the same for everyone, not just those who’ve had treatment like Princess Catherine. They include not smoking, eating a nutritious and balanced diet, exercising regularly, cutting down on alcohol and staying sun smart.

Amali Cooray, PhD Candidate in Genetic Engineering and Cancer, WEHI (Walter and Eliza Hall Institute of Medical Research) ; John (Eddie) La Marca, Senior Research Officer, Blood Cells and Blood Cancer, WEHI (Walter and Eliza Hall Institute of Medical Research) , and Sarah Diepstraten, Senior Research Officer, Blood Cells and Blood Cancer Division, WEHI (Walter and Eliza Hall Institute of Medical Research)

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Receiving a cancer diagnosis is life-changing and can cause a range of concerns about ongoing health.

Fear of cancer returning is one of the top health concerns. And managing this fear is an important part of cancer treatment.

But how likely is it to get cancer for a second time?

Why can cancer return?

While initial cancer treatment may seem successful, sometimes a few cancer cells remain dormant. Over time, these cancer cells can grow again and may start to cause symptoms.

This is known as cancer recurrence: when a cancer returns after a period of remission. This period could be days, months or even years. The new cancer is the same type as the original cancer, but can sometimes grow in a new location through a process called metastasis.

Actor Hugh Jackman has gone public about his multiple diagnoses of basal cell carcinoma (a type of skin cancer) over the past decade.

The exact reason why cancer returns differs depending on the cancer type and the treatment received. Research is ongoing to identify genes associated with cancers returning. This may eventually allow doctors to tailor treatments for high-risk people.

What are the chances of cancer returning?

The risk of cancer returning differs between cancers, and between sub-types of the same cancer.

New screening and treatment options have seen reductions in recurrence rates for many types of cancer. For example, between 2004 and 2019, the risk of colon cancer recurring dropped by 31-68%. It is important to remember that only someone’s treatment team can assess an individual’s personal risk of cancer returning.

For most types of cancer, the highest risk of cancer returning is within the first three years after entering remission. This is because any leftover cancer cells not killed by treatment are likely to start growing again sooner rather than later. Three years after entering remission, recurrence rates for most cancers decrease, meaning that every day that passes lowers the risk of the cancer returning.

Every day that passes also increases the numbers of new discoveries, and cancer drugs being developed.

What about second, unrelated cancers?

Earlier this year, we learned Sarah Ferguson, Duchess of York, had been diagnosed with malignant melanoma (a type of skin cancer) shortly after being treated for breast cancer.

Although details have not been confirmed, this is likely a new cancer that isn’t a recurrence or metastasis of the first one.

Australian research from Queensland and Tasmania shows adults who have had cancer have around a 6-36% higher risk of developing a second primary cancer compared to the risk of cancer in the general population.

Who’s at risk of another, unrelated cancer?

With improvements in cancer diagnosis and treatment, people diagnosed with cancer are living longer than ever. This means they need to consider their long-term health, including their risk of developing another unrelated cancer.

Reasons for such cancers include different types of cancers sharing the same kind of lifestyle, environmental and genetic risk factors.

The increased risk is also likely partly due to the effects that some cancer treatments and imaging procedures have on the body. However, this increased risk is relatively small when compared with the (sometimes lifesaving) benefits of these treatment and procedures.

While a 6-36% greater chance of getting a second, unrelated cancer may seem large, only around 10-12% of participants developed a second cancer in the Australian studies we mentioned. Both had a median follow-up time of around five years.

Similarly, in a large US study only about one in 12 adult cancer patients developed a second type of cancer in the follow-up period (an average of seven years).

The kind of first cancer you had also affects your risk of a second, unrelated cancer, as well as the type of second cancer you are at risk of. For example, in the two Australian studies we mentioned, the risk of a second cancer was greater for people with an initial diagnosis of head and neck cancer, or a haematological (blood) cancer.

People diagnosed with cancer as a child, adolescent or young adult also have a greater risk of a second, unrelated cancer.

What can I do to lower my risk?

Regular follow-up examinations can give peace of mind, and ensure any subsequent cancer is caught early, when there’s the best chance of successful treatment.

Maintenance therapy may be used to reduce the risk of some types of cancer returning. However, despite ongoing research, there are no specific treatments against cancer recurrence or developing a second, unrelated cancer.

But there are things you can do to help lower your general risk of cancer – not smoking, being physically active, eating well, maintaining a healthy body weight, limiting alcohol intake and being sun safe. These all reduce the chance of cancer returning and getting a second cancer.

Sarah Diepstraten, Senior Research Officer, Blood Cells and Blood Cancer Division, Walter and Eliza Hall Institute and Terry Boyle, Senior Lecturer in Cancer Epidemiology, University of South Australia

This article is republished from The Conversation under a Creative Commons license. Read the original article.