How much will chemotherapy really help you? (Dec-08)

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After breast cancer surgery, additional treatments such as chemotherapy can reduce the risk of cancer coming back. But do women understand how much (or little) benefit chemotherapy provides? Imagine that you're a woman who has recently been diagnosed with breast cancer and then had the cancerous breast tumor surgically removed. While you're at an appointment about 3 weeks after your surgery, your doctor says the following to you:

"Sometimes cancer cells remain after surgery and start to grow again. To try to prevent your cancer from growing again, you should consider having some additional treatment.

"One of our test results shows that you have a type of cancer that is estrogen receptive (ER) positive. This means that your cancer needs the hormone estrogen in order to grow.

"Because you have an ER-positive tumor, you should have hormonal therapy to block estrogen and make it harder for any remaining cancer cells to grow. Hormonal therapy is usually in pill form. It does not cause hair loss or fatigue and generally has very few short-term side effects. You'll start to take hormonal therapy after all other treatments are finished and continue to take it for at least 5 years.

"Although it's clear that you should have hormonal therapy, you'll still need to make a choice about chemotherapy treatments. You could decide to have additional chemotherapy treatments for several months before starting the hormonal therapy. Sometimes, adding chemotherapy can make a big difference in decreasing the risk of dying from cancer. Other times, there's almost no benefit from adding chemotherapy.

"If you decide to have chemotherapy, you'll have 2 to 4 months of fatigue, nausea, hair loss, and other side effects. You'll also face a small risk (less than 1% or less than 1 in 100) of getting a serious infection, a bleeding problem, heart failure, or leukemia. Only you can decide if the benefit of adding chemotherapy to hormonal therapy is worth the risks and side effects."

Next, your doctor shows you a graph that may help you to decide about chemotherapy.

Your doctor says, "The graph below may help you decide if the risk reduction you would get from adding chemotherapy is worth the side effects and risks that the chemotherapy would cause.

  • The green part shows the chance that you'll be alive in 10 years.
  • The red part shows the chance that you'll die because of cancer.
  • The blue part shows the chance that you'll die from other causes.
  • The yellow part shows how much your chance of being alive in 10 years would increase if you add a therapy.
"Remember, given your situation, I think you should definitely take hormonal therapy. What you need to decide is whether to take both chemotherapy and hormonal therapy."
 
In interpreting this graph, imagine that there are two groups of 100 women each. All of these women have the same type of cancer as your hypothetical cancer.
  • The first group all decides to take hormonal therapy only.
  • The second group all decides to take both chemotherapy and hormonal therapy

How many fewer women will die from cancer in the second group, as compared with the first group?

Your doctor continues, "Now, here is another graph that shows the same information in a different way. As before,

  • The green part shows the chance that you'll be alive in 10 years.
  • The red part shows the chance that you'll die because of cancer.
  • The blue part shows the chance that you'll die from other causes.
  • The yellow part shows how much your chance of being alive in 10 years would increase if you add a therapy.
Now we asked you to consider the following question:
How many fewer women will die from cancer in the second group, as compared with the first group?
Do you want to change your answer?
 

About the study

Many participants who saw this graph in a study conducted by CBDSM researchers had similar problems. However, when study participants saw GRAPH B (with the two pictographs), many more were able to correctly calculate the difference.

The CBDSM study compared tools intended to help cancer patients make informed decisions about additional therapies (also called "adjuvant" therapies). The 4 horizontal stacked bars were taken from an online tool called "Adjuvant!" that is often used by physicians to explain risk to cancer patients. The researchers compared comprehension of risk statistics from horizontal bars and from a pictograph format.

They found that study participants who viewed a 2-option pictograph version (GRAPH B in this Decision of the Month) were more accurate in reporting the risk reduction achievable from adding chemotherapy to hormonal therapy for the hypothetical cancer scenario. With GRAPH B, 77% of participants could identify that 2 fewer women out of 100 would die from cancer with both chemotherapy and hormonal therapy. With the 4 horizontal bars (GRAPH A), only 51% of participants could make this calculation. Participants who saw GRAPH B were also much faster at answering this question than participants who saw GRAPH A.
In addition, participants in this study strongly preferred the format of the pictograph you saw (GRAPH B) to the bar graphs you saw (GRAPH A).
The researchers comment:
"While decision support tools such as Adjuvant! use graphical displays to communicate the mortality risks that patients face with different adjuvant therapy options, our research shows that women had difficulty interpreting the 4-option horizontal bar graph format currently used by Adjuvant!. Two simple changes, displaying only risk information related to treatment options that included hormonal therapy...and using pictographs instead of horizontal bars, resulted in significant improvements in both comprehension accuracy and speed of use in our demographically diverse sample....The results...support the concept that simpler information displays can make it easier for decision makers to implement optimal decision strategies. Specifically, focusing patients' attention on those treatment options currently under consideration while removing information related to options which have been already eliminated from consideration (for medically appropriate reasons) may be particularly beneficial. In the context of adjuvant therapy decisions, such an approach would imply that clinicians should discuss the decision in two stages: A first stage in which hormonal therapy is considered and a second stage in which the incremental benefit of chemotherapy is evaluated...Adjuvant! and other online risk calculators enable oncologists and patients to receive individually tailored estimates of mortality and recurrence risks, information that is essential to informed decision making about adjuvant therapy questions. Yet, the full potential of these modeling applications cannot be realized if users misinterpret the statistics provided."
 
Read the article:
Zikmund-Fisher BJ, Fagerlin A, Ubel PA. Cancer 2008;113(12):3382-3390.