Researchers at Melbourne are embarking upon a worldwide study to see if there is a risk of relapse of cancers among persons who have undergone surgeries. The team hypothesizes that while undergoing a surgery using gas anesthetics, those with cancer are at a greater risk of a cancer relapse. 

There have been previous studies in laboratory mice that have shown this phenomenon to be true. Peter MacCallum Cancer Centre's Bernhard Riedel is the lead investigator of this study.

He assures that this hypothesis should not alarm patients and quite a few hospitals have already switched to intravenous anesthetic agents from the earlier used gas anesthetic agents for conducting cancer surgeries. This new study would be conducted over five years and would include 5,700 patients.

Riedel says once the results are out, cancer surgeries across the world would change. He said that there was “mounting evidence” against the use of gas or volatile inhaled anesthetic agents among cancer patients. He said that evidence shows that these anesthetic agents are capable of promoting the growth of the remaining cancer cells within the body.

Riedel explained that in the lab study mice with cancers were treated with intravenous anesthesia and gas anesthesia for surgeries to remove their tumors. Survival was longer when intravenous anesthetics were used.

“There is some literature that is suggesting that some of the volatile gases may drive some of the cancer pathways, and so if there's any residual disease or cancer that's left undiagnosed at the time of surgery, this has a chance to get a foothold and lead to recurrence,” he explained. He added that gases as such do not cause cancers but may just “add fuel to the fire.”

According to Riedel, based on this preliminary evidence, many hospitals have already switched to intravenous anesthesia over gas anesthetics and this study would provide a more concrete evidence of this fact.

He reiterated that gas anesthetics were safe saying, “The workhorse of anesthesia has always been volatile-based anesthesia, it's used by the majority of anesthetists, it is safe."

"The volatilize easy to turn on, they are titratable they are easy to switch off, they have been the primary technique used anesthetists for decades the opportunity to study this and see whether we can make it a little bit safer for the cancer patient is important,” said Riedel.

Riedel and his team write in the study synopsis that 80% of the anesthetists still routinely use gas anesthesia or inhaled anesthetic gases and half of them believed that anesthesia choices had an impact on the cancer prognosis or outcome.

The synopsis states, “This lack of clinical consensus on optimal anesthesia reflects the need for a definitive randomized clinical trial.” At present millions of Australians are receiving either gas anesthetics or both intravenous and gas anesthetics for their surgery annually.

Around 60% of these patients come back with a recurrence of their cancers within five years, the synopsis said. Propofol, an intravenous agent, that is widely used for anesthesia would be tried and assessed if it was safer for patients with lung and bowel cancers.

The new study would be with the collaboration of Peter MacCallum Cancer Centre and the University of Melbourne and has the funding to the tune of $4.88 million from the Federal Government.