General anesthesia unlikely to provoke cancer development
MedWire News: General anesthesia does not appear to increase people's risk for developing cancer, say researchers who found that the duration and depth of anesthesia are not associated with subsequent rates of malignancy.
It has been hypothesized that the temporary immunosuppression associated with general anesthesia may allow quiescent malignant cells to develop into clinical disease. The current study, which appears in the journal Anesthesia and Analgesia, does not support this hypothesis.
But the researchers caution: "Our results may not be valid in patients with previous malignancy or those undergoing cancer surgery, in whom the relationship between tumor burden and immunocompetence may be different."
Maj-Lis Lindholm (Karolinska Institute, Stockholm, Sweden) and colleagues assessed the outcomes of 2792 cancer-free patients who were anesthetized with sevoflurane. Over the next 5 years, 4.3% of these patients were diagnosed with one or more malignancies.
The rate of cancer diagnosis rose with patient age, from 1.9 per 1000 person-years for those younger than 30 years to 31.1 per 1000 person-years for patients aged 70 years or more.
Rates of cancer diagnosis ranged from 5.8 per 1000 person-years for patients in the bottom quartile of anesthesia duration (≤1.10 h) to 11.8 per 1000 person-years for those in the top quartile (≥2.29 h). These differences were not significant after accounting for age, gender, body mass index, American Society of Anesthesiologists physical status, type of surgery, smoking, and number of other surgical procedures during follow-up. There were also no differences when anesthesia duration was analyzed by per hour increase.
The team used time spent with a bispectral index (BIS) of less than 45 as an indicator of profound anesthesia. The cancer diagnosis rates for patients in the bottom and top quartiles of time under profound anesthesia (≤0.72 and ≥1.86 h, respectively) were 8.2 and 9.5 per 1000 person-years, respectively. There were no significant differences after multivariate adjustment or when using different BIS thresholds.
Editorialists Kate Leslie (Royal Melbourne Hospital, Australia) and Timothy Short (Auckland City Hospital, New Zealand) called the findings "good news," saying that it would be "deeply ironic and very sad if anesthesia, regarded as one of the most important medical discoveries of all time, proved to be harmful to the long-term health of our patients."
They added: "This result may give pause to researchers considering a large randomized trial on the effect of long duration or deep general anesthesia on death from cancer, because it suggests that, if there is a small effect that has been missed by this study, a very large and expensive trial would be required to detect it."
By Eleanor McDermid