When is cancer considered cured, versus in remission?

After a patient has undergone treatment for cancer, they may be told that the disease is either in "remission" or that they have been "cured." But there's a distinction between these terms.

So what does it mean for cancer to be in remission, and what does it mean to have been cured?

First, it's important to note that there are two types of cancer remission: "complete remission" and "partial remission." Complete remission means that a person's cancer is responding to treatment, that they have no signs or symptoms of the disease, and there are no cancerous cells in their body that can be detected by a scan or a blood test, for instance.

Partial remission means that treatment is working but that tests show some cancerous cells remain in the body. In contrast, when a patient has "stable disease," it means their condition is neither improving nor worsening in response to treatment.

Doctors can't predict how long remission will last, so there's a chance the cancer could come back. Remission can last weeks or years.

Related: What are cancer vaccines?

If a patient remains in complete remission for five years or more, then some doctors may say the patient is "cured," which means they've shown a long-term absence of symptoms or signs of cancer.

However, even if a patient is considered cured, they may still have undetected cancer cells lurking in their body that may cause a recurrence of the disease one day. Doctors may be more likely to say that a patient is "cured" if they have a type of cancer that has a high five-year cancer survival rate when detected early, such as breast cancer or melanoma, which is a type of skin cancer.

Epidemiologists may also use a term known as "statistical cure" in this context. This means that a patient survives long enough that their risk of death from cancer returns to that of the general public, Dr. Vijay Trisal, a surgical oncologist at the City of Hope cancer research center in California, told Live Science.

For instance, if someone had colon cancer 10 years ago and now they are free of the cancer, their risk of dying from the disease has effectively gone back to the baseline risk that would be expected of other people their age, he added.

Nevertheless, the term "cure" should be used with caution, Trisal said. Although it may alleviate some patients' anxiety and allow them to resume their normal lives, it can make others less vigilant and more likely to avoid future tests and screening that could help detect reoccurrence, he added.