Racial bias on the part of a doctor can lead to poor communication and medical treatment for black cancer patients, a U.S. study suggests.

Researchers who analyzed video-recorded discussions between oncologists and African-American patients found that biased doctors spent less time with patients, and patients had a harder time remembering the contents of the conversation.

Many people have some level of implicit racial bias, and doctors are no different, said lead author Louis A. Penner of the Karmanos Cancer Institute in Detroit, Michigan.

Nonconscious, or implicit, bias "is an automatic response that typically occurs without a person being aware of it," Penner told Reuters Health by email.

There are still pervasive disparities in cancer treatment quality for black and white patients, and the new study was designed to see if implicit racial bias may contribute to those disparities, though it is not the only cause, he said.

The researchers studied 18 non-black medical oncologists and 112 of their new black patients at cancer hospitals in Detroit. The doctors completed an implicit racial bias test beforehand.

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Most oncologists were men and most patients were women. In general, the doctors had small to moderate levels of implicit racial bias, lower than national averages but consistent with averages in the Detroit area.

Several weeks later, the researchers recorded videos of each doctor's interactions with patients, timed the conversations and had patients complete a survey about the interaction, their levels of distress and trust and their perceptions of the recommended treatment.

On average, oncologists and patients were in the room together for 30 minutes and oncologists talked almost four times as much as their patients, according to the results in the Journal of Clinical Oncology.

Oncologists with higher levels of implicit racial bias had shorter interactions, and patients rated their interactions as less patient-centered and supportive. Their patients also had a harder time remembering what was talked about and tended to have less confidence in the recommended treatments, as rated by the patients themselves and the researchers after viewing the recorded conversations.

"This is compelling evidence that implicit racial biases on the side of providers affects how they interact with patients," said Adam T. Hirsh of Indiana University-Purdue University Indianapolis, who was not part of the new study.

Implicit racial bias may have more of an influence on the process of care than on outcomes, but we should be cautious about concluding they have no effect on outcomes, Hirsh told Reuters Health by phone.

"If we have poor or less than optimal interpersonal interactions with physicians or providers, that's going to impact our healthcare use in the future," he said.

Ironically, implicit bias is most likely to affect behavior when people are "cognitively overloaded," taking in lots of information at once and having to make decisions in uncertain circumstances, which is exactly what happens at an oncology appointment, he said.

"The surprising part to me is that black cancer patients, in the midst of all the other things they must be thinking as they deal with their cancer, can detect this bias in the behavior of their physician," Penner said. Both patients and independent observers picked up on implicit bias, he said.

"If you think your physician doesn't care about you and/or you can't trust them, this almost certainly affects how much confidence you have in his/her treatment recommendations," Penner said.

Reducing implicit racial bias in cancer interactions will not, by itself, eliminate treatment disparities, but could play a significant role, he said.

"There is evidence that medical students' exposure to diversity in medical school affects their subsequent levels of implicit bias," he added.

"Physicians also need more training in communicating easily and effectively with all their patients," Penner said. "The better physicians are at communicating effectively, the more at ease physicians are in their communication, the less likely it is that implicit bias will affect their verbal and nonverbal behaviors when they interact with black patients."