Study assesses possible links between pain medications and recurrent breast cancer risk

Women who receive one common pain drug during mastectomy are less likely to develop recurrent breast cancer in the years following surgery, suggests a study in the June issue of Anesthesia & Analgesia, official journal of the International Anesthesia Research Society (IARS).

The study adds to a growing body of intriguing but preliminary evidence—outlined in an accompanying research review and editorial—that anesthetic and analgesic drug choices may, through their effects on the immune system, have an impact on the outcomes of cancer surgery.

Ketorolac Linked to Lower Rate of Recurrent Breast Cancer

Dr. Patrice Forget and colleagues of Université Catholique de Louvain, Belgium, assessed possible links between pain medications and recurrent cancer risk in 327 women undergoing mastectomy for breast cancer. Recurrence rates at one to four years after surgery were compared for patients who received different drugs for pain during their surgery.

Women receiving ketorolac—a powerful prescription nonsteroidal anti-inflammatory drug (NSAID), related to aspirin and ibuprofen—seemed to be at lower risk of recurrent breast cancer. The recurrence rate was 6 percent for women who received ketorolac during their mastectomy versus 17 percent for those who did not receive ketorolac. (The overall recurrence rate was 11 percent.)

The lower risk of recurrent cancer was still significant after adjustment for other factors, including the patient's age and the stage of the cancer. None of the other pain medications used during surgery affected the recurrence rate.

Further Evidence that Anesthetics and Analgesics Could Affect Cancer Risk

It may seem strange that giving a drug for pain could influence the risk of cancer recurrence. Yet the study is only the latest addition to a growing body of evidence suggesting that anesthetic and analgesic (pain-relieving) drugs could affect cancers.

Dr. Antje Gottschalk of University of Virginia, Charlottesville, and colleagues, reviewed the evidence. "A wealth of basic science data supports the hypothesis that the surgical stress response increases the likelihood of cancer dissemination and metastasis during and after cancer surgery," they write. For example, it has been clearly shown that opioid drugs, such as morphine, inhibit immune responses in humans.

During cancer surgery, cancer cells are released into the bloodstream. Theoretically, the use of drugs that lessen immune responses could reduce the body's ability to kill these disseminated cancer cells—thus potentially increasing the chances that the cancer could come back. The authors emphasize that there is no evidence showing a link between opioid pain medications and cancer recurrence risk in humans, although "animal data strongly suggest that they may contribute to cancer recurrence."

There is also evidence of a similar effect of commonly used inhaled anesthetics, according to an accompanying editorial by Dr. James G. Bovill of Leiden University Medical Center. It has even been proposed that reductions in immune system function related to surgical anesthetics could lead these otherwise-dormant cancer cells to become activated.

There are several promising approaches to avoiding the potential effects of anesthetics/analgesics on cancer risk, According to Dr. Gottschalk and colleagues: using regional anesthesia when possible, minimizing doses of opioid drugs, and using NSAIDs that work in the same way as ketorolac. Dr. Bovill emphasizes the need for well-designed scientific trials to prove or disprove the effects of anesthetics and analgesics on recurrent cancer risk. He writes, "Without the results from such studies, we cannot make the informed judgments that will allow us to offer safe anesthesia to our patients while avoiding the devastating consequences of cancer long after the anesthetic has worn off."