CANCER
March 8, 2017

The Calculations of Cancer Patients

Weighing the pros and cons of treatment options is not easy for patients, particularly when they are reeling from a cancer diagnosis. It doesn't have to be so hard.

The information available to patients can be overwhelming, making choosing between medical treatments difficult. It is especially hard because weighing the pros and cons, risks and benefits is not easy. And it can be really challenging for people who find math difficult and who are dealing with a possibly lethal illness at the same time. How can you judge risks and benefits of treatment options when the numbers make no sense?

Ellen Peters, a professor of psychology from Ohio State University, has authored and co-authored several papers on the role of numeracy — the ability to understand and work with numbers — in decision making. At this year's American Association for the Advancement of Science (AAAS) annual meeting she and her colleagues presented another study showing that people with low numeracy — the math-challenged — tend to suffer more when it comes to their health.

“It is absolutely OK to tell the doctor that this is too complicated.”

An earlier study looked at breast cancer patients who had undergone early-stage breast cancer surgery and were presented with options for further treatment — including hormonal treatment, chemotherapy, combined treatment or no treatment. Each patient was also given statistics on how likely she was to survive 10 years cancer-free with each possible treatment plan, based on their specific case.

Each woman was asked to estimate how likely she thought she was to survive the next 10 years cancer-free with each of the treatments.

Overall, the women's estimates were more pessimistic than those they had been given. But women with better math skills gave estimates that were much more in line with the numbers that they had been shown.

“For those who were less numerate, their survival estimates were pessimistic, but remained the same no matter what numbers they were presented. It was as if they didn't read the numbers at all,” Peters said, in a statement. “This is critical. We were giving them information that should help them choose the best treatment, but they were ignoring it.” Peters doesn't blame the patients. If the information had been presented in a more user-friendly manner, more women would have understood it, she believes.

And it's not only the math-challenged who had difficulty. Overall, 30 to 40 percent of the women did not correctly identify which treatment gave them the best chance of cancer-free survival. The numbers generally used to describe risk and benefit seem complicated to nearly everyone.

What can people, especially those who struggle with numbers, do? Peters said research suggests four strategies:

  • Ask for the numbers and look at them. Give them a chance. Without these numbers, you have nothing to go on but intuition and guesswork. And sometimes they are compelling enough to clearly point the way to a decision.
  • Ask what the numbers mean. Your doctor should be able to explain them in practical terms. An example: "If 80 percent of people are helped by this particular drug, is that good or bad? Ask your doctor to say if this is above or below average, if it is a fair, good or excellent treatment compared to other options," Peters suggests.
  • Cut down the choices. If you're given a long list of possible treatments, ask your doctor to choose the best two options. “It is absolutely OK to tell the doctor that this is too complicated,” says Peters. “You don't need to have doctors make a treatment decision for you, but they should be able to identify the most critical information for you to consider.”
  • Ask for the absolute risk. Knowing that one drug has twice the risk of causing a particular side effect that another drug does (relative risk) makes it sound like there's a large difference between them. But it may be a very small increase, from 0.01 percent to 0.02 percent. On the other hand, it might be a much larger increase from 10 percent to 20 percent. You'll never know unless you ask for the absolute risk, which is usually more helpful in making a decision.
  • Yes, it would be best if your doctor or nurse provided the numbers in a way that you could understand, but if they don't, it's up to you to ask for help.

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