Oncologists Influence Peers in Prescribing Novel Therapies

A new study finds that leveraging physician ties can promote targeted adoption of high-value therapies.

As part of the longitudinal study published in JAMA, researchers constructed physician networks (or clusters) using Medicare claims to identify physician pairs who had previously shared patients within a single episode of cancer care from 2005 to 2006. Oncologists who had prescribed cancer drug bevacizumab within this baseline period were matched with those who prescribed the biological product during the three years after its approval (from 2007 to 2010) to make the assessments.

The aim was to assess the extent to which bevacizumab use by a physician’s community of connected physician peers in the earlier period was associated with the physician’s later use.

After adjustment, bevacizumab adoption in the years after its approval was found to be greater if physician peers were earlier adopters of the cancer drug. The increase among connected physicians was greater even after accounting for practice-level influences. The rate of bevacizumab use relative to other chemotherapy by tertile of use among later adopters was 10.0 percent, 9.5 percent, and 13.6 percent, respectively. And for all patients receiving chemotherapy, the receipt of bevacizumab was less than 4.4 percent, between 4.4 percent to 6.2 percent, and more than 6.2 percent, respectively.

Citing the characterized use of bevacizumab within a community of physicians, the researchers argue that their study suggests “an important role of social reinforcement among physicians, rather than just the communication about a medical innovation from a colleague.” This, in turn, suggests that bevacizumab adoption is a complex contagion that requires social reinforcement.

It is not an unusual practice for physicians to follow the lead of their physician peers, especially when characteristically similar. There is consistency with similar studies from 2017 and 2018 on peer influence over the adoption of new medical technologies to treat various health conditions.

But the bandwagon effect that takes place can be better leveraged to promote high-value adoption.

A growing body of research indicates that physicians are reluctant to adopt new medical products until they see their physician peers using them. The researchers note that this suggests exposure to new drugs prescribed by another physician increases knowledge about them and comfort prescribing them.

Findings underscore the importance of understanding the profile of new cancer therapies for purposes of increasing the adoption of therapies with use indications of high-value. They shed light on prescribing practices at a time when novel systemic therapies to treat cancer types have come under the spotlight because of the ever-increasing number of new approvals and costs.

Only the reference drug, sold under the name Avastin, was available at the time when the study took place. The first biosimilar Mvasi became available in 2017, followed by ZIRABEV just last year. Cancer drug approvals increased from just 4% of the US total in the 1980s to 27% between 2010 and 2018, according to the Tufts Center for the Study of Drug Development.  

An observational study published in 2018 found bevacizumab use rapidly diffused among oncology practices from the time its procedure code became available in 2005 through 2012.

Still, the new study seeks to inform the issue of a lingering wide variation in existing prescribing practices. This variation was seen across oncology practices in the 2018 study, with study authors observing this to have been particularly evident for indications of lower-value.

With the variation in physicians’ use of bevacizumab, there is also a reported discrepancy between the prices of new cancer drugs and those with high-value indications that dates back several years. And with policymakers coming increasingly under pressure to combat soaring drug prices as cancer drugs continue to proliferate the market amid the shift to value-based payments, physician interventions are key.

Previous researchers called for interventions targeted at physician practices for decreasing low-value use of high-cost cancer therapies. Pointing to the Oncology Care Model for physician reimbursements, the new study argues for such interventions to be more specifically targeted at physician ties to their peers.

"Current efforts to promote delivery of high-value oncology care,” write Keating et al., “target physician organizations, a strategy that, in part, relies on the development of practice norms that arise in response to these incentives. Such initiatives are rooted in the expectation that individual physicians can influence the practice of their peers. However, physician behavior is quite challenging to change, and relatively few studies have demonstrated the ability of physicians to directly influence clinical decisions of others.”

With the ongoing value-based payment reform efforts and the deluge of drug pricing policy proposals, the implications of the findings are threefold. Interventions that leverage physician ties have the potential of not only increasing update of new, high-value cancer therapies, but also let up that of low-value therapies.

“Moreover, understanding which physicians to target is also important,” the researchers add. They cite research suggesting that academic detailing has the potential to influence clinician behavior and this being especially true “if targeted to key opinion leaders who are perceived as influential experts by their peers.” Past research also indicates that social influence can generate learning dynamics that improve performance in decentralized networks, posing the potential to slow the adoption of low-value therapies.