Chemotherapy: How framing bias leads to wrong decisions in treatment of cancer
A recent article in ICNR raises fundamental questions on whether Chemotherapy has been oversold. Research done by 3 oncologists in Australia and the US published in the Australian Journal Clinical Oncology titled “The Contribution of Cytotoxic Chemotherapy to 5-year Survival in Adult Malignancies” found that chemotherapy contributes just over 2 percent to improved survival in cancer patients.
Why then are well meaning doctors making the mistake of prescribing their patients with wrong treatment regimen? Brain’s ability to understand and process complex information is quite poor and how the situation is framed would lead to decisions that are not entirely rational. In this case, the results of oncology treatments were framed as relative risk and not as absolute risk as pointed out by the authors.
For example, oncologists frequently express the benefits of chemotherapy in terms of what is called “relative risk” rather than giving a straight assessment of the likely impact on overall survival. Relative risk is a statistical means of expressing the benefit of receiving a medical intervention in a way that, while technically accurate, has the effect of making the intervention look considerably more beneficial than it truly is.
If receiving a treatment causes a patient’s risk to drop from 4 percent to 2 percent, this can be expressed as a decrease in relative risk of 50 percent. On face value that sounds good. But another, equally valid way of expressing this is to say that it offers a 2 percent reduction in absolute risk, which is less likely to convince patients to take the treatment.
Experiments done by Kahneman & Tversky establish how the brain processes losses and gains differently and thus leading to different decisions. The following experiment conducted amongst a large sample of physicians illustrates this behaviour.
The U.S. is preparing for the outbreak of an unusual Asian disease, which is expected to kill 600 people. Two alternative programs to combat the disease have been proposed. Assume that the exact scientific estimates of the consequences of the programs are as follows: – If program A is adopted, 200 people will be saved. – If program B is adopted, there is a one-third probability that 600 people will be saved and a two-thirds probability that no people will be saved. Which of the two programs would you favor?
72 percent of those physicians who took part in the experiment chose option A, which was seen as a safe option. But look at what happens when the same probability is framed differently.
The U.S. is preparing for the outbreak of an unusual Asian disease, which is expected to kill 600 people. Two alternative programs to combat the disease have been proposed. Assume that the exact scientific estimates of the consequences of the programs are as follows: – If program C is adopted, 400 people will die – If program D is adopted, there is a one-third probability that nobody will die and a two-thirds probability that 600 people will die. Which of the two programs would you favor?
Only 22 percent in this case chose option C and the remaining 78 percent chose option D. When the problem is framed in terms of losses rather than gains, the decision changed, though the probability of survival is just the same. While this is completely irrational behaviour, it is systematic and hence predictable and repeatable because of the way our brain is wired.
This understanding opens up interesting possibilities in influencing social behaviour in ways that are favourable to society and thus more effective application of government spending.