A consensus statement on the possible link of anesthetic technique and anesthetic agents to risk for cancer and cancer recurrence underscores lack of definitive evidence and the need for further research. The statement was recently published in the British Journal of Anaesthesia.
The experts concluded that, although there are conflicting views on whether anesthetic technique might affect cancer outcome, “there is currently insufficient evidence to support any change in clinical practice.” The statement also noted that randomized clinical trials are needed to evaluate the effect of drugs on cancer recurrence and metastasis. According to the experts, current data on opioids suggest either a protective or no effect for cancer. The statement said that there is no evidence that morphine analgesia causes cancer, but whether opioids affect the risk for recurrence after cancer surgery remains unclear.
“Although it is by no means unanimous, the balance of available evidence from laboratory cancer cell cultures, live animal models, clinical retrospective analyses and translational studies from patients randomized to a prospective trial suggests that certain anesthetic and analgesic techniques may be more beneficial than others in cancer,” said Donal J. Buggy, MD, professor of anesthesiology at University College Dublin, Ireland, in an email to Anesthesiology News. Dr. Buggy ran the two-day BJA workshop at the College of Anaesthetists of Ireland, in Dublin.
Daniel I. Sessler, MD, who attended the meeting and signed the consensus statement, toldAnesthesiology News that in addition to regional analgesia, there are two drug classes of particular interest: lidocaine, delivered intravenously, and the nonsteroidal analgesic class of cyclooxygenase (COX)-2 inhibitors.
“Both have been shown in mechanistic and animal studies to either inhibit cancer or enhance immune function in ways that should reduce the risk for cancer recurrence. The primary defense against new cancers and cancer recurrence is natural killer cells. The problem is that natural killer cell function is impaired by the surgical stress response by volatile anesthetics and by opioids,” explained Dr. Sessler, who is Michael Cudahy Professor and Chair, Department of Outcomes Research at the Cleveland Clinic in Ohio. “Regional analgesia reduces the surgical stress response and decreases the need for volatile anesthetics and opioids. Intravenous lidocaine is anti-inflammatory and appears to enhance natural killer cell function, and the same is true for COX-2 inhibitors. In theory, then, either or both might be helpful.”
Dr. Sessler emphasized that this is still just theory, and the most important takeaway from the consensus panel is that there is good reason for doing research, but there isn’t enough data to suggest changes in practice.
Jonathan Moss, MD, PhD, professor of anesthesiology and critical care at The University of Chicago, agreed that this is the best course of action until there is strong evidence supporting a need for change.
“A lot of times these retrospective studies have confounding variables that we don’t understand,” said Dr. Moss. “I think, as a clinician, opioids are extremely useful. And we don’t want to scare our patients.”
Dr. Moss was also present at the BJA meeting but did not sign the consensus because he and others have done cellular, molecular and animal work suggesting that opiate antagonism may influence cancer progression in these model systems. He noted that he is a developer of the peripheral opiate antagonist methylnaltrexone and receives royalties from its sale as well as consulting fees from Salix Pharmaceuticals.