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Figure  . Discussing risk in relative terms may confuse patients.

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The type of statistic oncologists use to present recurrence risk to women considering adjuvant chemotherapy for breast cancer can have a significant impact on whether the women may choose to have the therapy, according to a recent study. Patients may make a more informed decision when the information is presented in terms of absolute survival benefit, researchers reported in the Journal of Clinical Oncology (2003;21:4,299–4,305).

Celia Chao, MD, and colleagues from the University of Texas Medical Branch in Galveston and the University of Louisville in Kentucky recruited 203 first- and second-year medical students for a study to determine which description of risk was easiest to understand and how different descriptions affected treatment choices.

The students were all presented with a scenario in which their mother was diagnosed with a node-negative, estrogen and progesterone receptor positive breast cancer. They were then asked to advise their mother, who according to the scenario had already undergone surgical resection and started tamoxifen, on whether to accept chemotherapy or not based on one of four descriptions of recurrence risk: relative risk reduction, absolute risk reduction, absolute survival benefit, or number needed to treat.

Participants who received information about relative risk were twice as likely to endorse chemotherapy as those given information about absolute survival benefit. But when quizzed about their mother's chances of surviving 10 years with the therapy, students who based their decision on relative risk were more often wrong about the actual benefits than students in the other groups.

These findings suggest that talking in terms of relative risk may lead patients to make treatment decisions that aren't fully informed, said lead author Chao, an Assistant Professor of Surgery at University of Texas Medical Branch in Galveston.

“We assume that patients understand, but really it's not that easy to grasp,” she said. “Anything we can do to make this decision-making process easier is the way to go.”

Speaking in terms of absolute survival benefit appears to give patients the best understanding of the potential effect of chemotherapy, she said.

In an editorial accompanying the article, H. Sam Wieand, PhD, explains that the absolute survival benefit cannot be determined from the relative risk reduction unless one also knows the probability of survival without treatment. Wieand, a Professor of Biostatistics at the University of Pittsburgh, presented two scenarios. In the first scenario, the probability of survival without chemotherapy is 98%, and the absolute survival benefit and relative risk reduction with chemotherapy are 1% and 50%, respectively. In the second, the chance of survival without chemotherapy is 50%. Although the relative risk reduction in this scenario is also 50%, the absolute survival benefit is 25%. Wieand suggested that far more patients would agree to undergo chemotherapy for an absolute survival benefit of 25% than for one of only 1%. However, presenting the patients only with the relative risk reduction would not distinguish between these two scenarios.

Another expert agreed with this conclusion. “I think absolute risk is better understood and the way most oncologists probably present risk,” said Jimmie Holland, MD, Professor and Vice Chair of Psychiatry and Behavioral Sciences at Memorial Sloan-Kettering Cancer Center in New York. “This [study] gives it some scientific underpinning.”

Open communication between doctor and patient is critical. Doctors must take the time to explain adjuvant therapy to patients, and they can use tools (such as graphs or charts) to help patients understand the risks and benefits of adjuvant chemotherapy, Chao said.

Holland said patients can do their part by learning as much about adjuvant chemotherapy as possible from sources like the American Cancer Society (ACS) and the National Comprehensive Cancer Network. Bringing a second person to the consultation or taping the discussion so it can be reviewed later also can be helpful, she added. And above all, patients “shouldn't be intimidated to ask questions because that's their right,” Holland said.

Chao said her study highlights a need for more research into what factors influence decisions about adjuvant treatment, which may be very different from factors that influence decision making in the metastatic setting. “Everyone has different motivations for choosing a therapy or not,” she said. “But to me, the basic understanding [patients must have] is that adjuvant therapy doesn't help everyone. It may increase your chance of a cure, but it can't guarantee it.”