Imagine you are standing in your garden, looking at the spot where a dandelion used to be. Even though the dandelion has been treated, you wonder, “What is the chance of finding new dandelions in the same flowerbed? In the other flowerbeds? Throughout the yard?” You cannot know for certain, so you have to guess. But your guess is not going to be some random number. You will consult your gardener, and together you will look for hints and signs to help you make an educated guess.
Your gardener will estimate the chance that a dandelion will return somewhere in your yard at some point in time. Like the gardener, your doctor does the same to predict the chances your cancer will recur (return). In the medical world, this estimate is known as a prognosis(PRAHG-NO-SIS) — A predicted outcome for groups of patients. It may seem simple, but it’s actually very hard to do, especially since it involves statistics.
Before we get too far, we need to clarify one thing. There are multiple types of prognosis, but to keep things simple, we are only going to talk about recurrence risk(REE-CER-ENCE RISK) — The chance a cancer will return in this article.
Recurrence risk is used for curable(CURE-A-BOWL) — The ability to eliminate all of the cancer without recurrence patients. So, if you have more advanced disease or incurable(IN-CURE-A-BOWL) — The inability to eliminate all of the cancer without recurrence cancer, your doctor will talk about different types of prognosis. These may include overall survival(O-VER-ALL SIR-VIVE-OL) — The expected time a patient will live after diagnosis (how long you may live with the cancer) or progression-free survival(PRO-GRES-SHUN FREE SIR-VIVE-OL) — The expected time a treatment will work before the cancer starts growing (how long a treatment(TREET-MINT) — Techniques to help eliminate or control a disease may work before the cancer starts growing).
The recurrence risk (relapse rates) is an estimate of the number of patients that will have their cancer recur after initial treatment.
Doctors use several factors to help them determine an individual’s prognosis. However, the stage of the disease is one of the most important factors in determining a prognosis.
Need a refresher on staging? Check out The Steps of Cancer Staging.
Let’s think about how the stage relates to the growth of dandelions.
You can have a small dandelion with no seeds and shallow roots or a large, deep-rooted dandelion with many seeds. It is easy to see how the seeded dandelion has a much higher chance of spreading and returning than the small one. Just like if there were more than one dandelion with seeds in a flowerbed, it would be even more likely for the seeds to spread.
But if you only look at the stage of the cancer, your educated guess may not be the best it can be. To make sure you have the most accurate estimate, you must look at other factors as well. For example, gardeners can also take the wind into consideration. The gardener can look at the direction of the wind and the speed of the gusts to determine how it will affect the spreading of seeds.
Luckily, unlike gardeners, doctors have very advanced tools that help them estimate the chance a patient’s cancer will return. Instead of an educated guess, these tools use complex mathematical calculations to predict a patient’s prognosis. Usually, doctors will give the estimates as percentages.
These percentages are based on groups of patients, not individuals. Each group is made up of thousands of patients in a similar situation (having similar cancer characteristics and health factors). These historical patients have been tracked, their information analyzed, and their outcomes recorded over many years to allow an individual patient to be summarized into a single percentage. All of the collected data has been consolidated and used to create predictive models, or advanced calculators. CancerSurvivalRates.com is one example of these advanced calculators (used for many types of cancer).1
Let’s use some actual numbers to help you grasp prognosis a little better.
To make this as easy as possible, let’s say the curable patient has a risk of recurrence prognosis of 50%. So we would say the patient has a 50% chance of their disease coming back and a 50% chance it will not.
Remember, these percentages only apply to large groups of people, not individuals. For an individual patient, the statistics become irrelevant. A single patient can have only one possible outcome: either the cancer recurs or it does not. So why does the doctor give you a number somewhere between 0 and 100 percent? The number reflects how many patients did recur in the group of historical patients with similar factors.
There are two main reasons why we must look at historical groups of patients. First, prognosis changes over time. For example, the longer you go without a recurrence(REE-CER-ENCE) — When a cancer returns or comes back, the more likely it is that you will not recur (for curable patients). Additionally, receiving treatment may improve a patient’s prognosis.
Second, it takes time to discover and fully know a patient’s outcome. It may take months, a few years, or even up to 20 years for a patient’s cancer to return. (How long it usually takes for a cancer to recur depends on the type of cancer). Most patients are given a percentage that estimates a prognosis in similar patients 5 years after diagnosis (sometimes 10 years), but not the full 20 years.
Finally, risk of risk of recurrence prognosisThe chance a cancer will return is used to guide treatment recommendations (if options are available). The doctor’s goal is to try to prevent the cancer from recurring in as many people as possible. So, if the chance of recurrence is high, a doctor may recommend more aggressive treatment (if available). Gardeners may do the same by using weed killers if they think the chance of a dandelion recurring is very high.
The goal is to give patients the best chance of their cancer not returning.
- Cancer Survival Rates. Courage Health. https://cancersurvivalrates.com. Accessed April 3, 2020.