In Contrast to Studies of Other Cancers, Risk Is Lower with General Anesthesia
Newswise — San Francisco, CA. (January 31, 2012) – For patients undergoing a minimally invasive treatment for liver cancer, the risk of recurrent cancer appears lower with general anesthesia compared to regional (epidural) anesthesia, reports a study in the February issue of Anesthesia & Analgesia, official journal of the International Anesthesia Research Society (IARS).
That's in contrast to studies of other types of cancer, which have found lower recurrence rates when cancer surgery is performed using regional anesthesia. "The benefit of regional anesthesia on cancer recurrence, to the extent that it exists, may depend on the specific tumor type," according to the new study, led by Dr Renchun Lai of Sun Yat-Sen University Cancer Center, Guangzhou, China.
General Anesthesia May Lower Recurrence Rate for HCC…
The researchers evaluated the effects of type of anesthesia on recurrence risk in patients with hepatocellular carcinoma (HCC), the most common type of liver cancer. The patients underwent a nonsurgical procedure called percutaneous radiofrequency ablation (RFA), in which a small probe is placed into the liver to destroy cancers using radiofrequency waves.
Dr Lai and colleagues examined the outcomes of 179 patients who underwent RFA for small HCCs between 1999 and 2008. The procedure was done using general anesthesia in 117 patients and epidural anesthesia in 62. Most familiar from its use during labor and delivery, epidural anesthesia is a type of regional anesthesia that numbs the lower body, but doesn't put the patient to sleep.
The researchers compared the risk of HCC recurrence among patients receiving general versus epidural anesthesia. In previous studies of surgery for several types of cancer—including colon, breast, and prostate cancer—recurrence rates have been lower with regional anesthesia.
However, in patients undergoing RFA for HCC, the opposite was true: the recurrence rate was lower with general anesthesia. With adjustment for other variables, including risk factors for recurrence, the risk of recurrent HCC was about four times higher for patients receiving epidural anesthesia.
However, the lower recurrence risk did not translate into an improved survival rate. Analysis of mortality rates found no significant difference in the long-term risk of death between the two anesthesia groups.
…But Many Questions Remain about Anesthesia and Cancer Surgery
Several recent studies have raised the possibility that the type of anesthesia used may affect the outcomes of cancer surgery. Most of those studies have found a lower recurrence risk when some type of regional anesthesia is used, rather than general anesthesia. One theory is that general anesthesia affects the immune system, allowing otherwise dormant cancer cells to progress into clinical disease.
However, the new study of patients undergoing RFA for HCC finds a lower recurrence rate after general anesthesia. It may be that the minimally invasive RFA procedure has less effect on the immune system compared to surgery, or that the effect of anesthesia on HCC recurrence differs from that for other cancers.
The new report, like previous studies of anesthesia and cancer recurrence risk, has an important weakness: it uses retrospective (looking backward) data on previously treated patients. "Such retrospective studies are very difficult to interpret because it is impossible to understand what risk factors were not evenly distributed among the patients," comments Dr. Steven L. Shafer of Columbia University, Editor-in-Chief of Anesthesia & Analgesia. He notes that prospective (looking forward) studies of how type of anesthesia affects the results of cancer surgery are underway.
One such study, led by Dr Daniel I. Sessler of The Cleveland Clinic, is being conducted to compare the risk of recurrent breast cancer in women undergoing mastectomy with general versus regional anesthesia. "There is overwhelming mechanistic support for regional analgesia protecting against cancer recurrence, along with strong animal data," comments Dr Sessler. "We and others have published both positive and negative retrospective studies. But all are small and suffer all the substantial limitations of observational analyses. Resolution of the question will have to await the results of randomized trials, including ours."
About the IARS
The International Anesthesia Research Society is a nonpolitical, not-for-profit medical society founded in 1922 to advance and support scientific research and education related to anesthesia, and to improve patient care through basic research. The IARS contributes nearly $1 million annually to fund anesthesia research; provides a forum for anesthesiology leaders to share information and ideas; maintains a worldwide membership of more than 15,000 physicians, physician residents, and others with doctoral degrees, as well as health professionals in anesthesia related practice; sponsors the SmartTots initiative in partnership with the FDA; and publishes the monthly journal Anesthesia & Analgesia in print and online.
About Anesthesia & Analgesia
Anesthesia & Analgesia was founded in 1922 and was issued bi-monthly until 1980, when it became a monthly publication. A&A is the leading journal for anesthesia clinicians and researchers and includes more than 500 articles annually in all areas related to anesthesia and analgesia, such as cardiovascular anesthesiology, patient safety, anesthetic pharmacology, and pain management. The journal is published on behalf of the IARS by Lippincott Williams & Wilkins (LWW), a division of Wolters Kluwer Health.