Malignant disease within 5 years after surgery in relation to duration of sevoflurane anesthesia and time with bispectral index under 45.

BACKGROUND

Surgery, general anesthesia, and related events have been implicated to promote cancer proliferation. We investigated the incidence of cancer within 5 years after surgery in relation to duration of anesthesia (T(ANESTH)) and also by time with bispectral index (BIS) under 45 (T(BIS<45)) serving as a proxy for more profound anesthesia exposure.

METHODS

New malignant diagnoses after surgery under sevoflurane anesthesia were obtained in a prospective cohort of 2972 BIS-monitored patients without any clinically diagnosed malignant disease at the time of index surgery. The risk of cancer during follow-up in relation to T(ANESTH) and T(BIS<45) was assessed by Cox regression. The cancer incidence in this surgical population was compared with the incidence in a standardized general population by calculation of standard incidence ratio.

RESULTS

One hundred twenty-nine patients (4.3%) were assigned 136 new malignant diagnoses within 5 years after surgery. No relation between T(ANESTH) or T(BIS<45) and new malignant disease was found, nor were any significant relations obtained when other thresholds for BIS (i.e., <30, <40, and <50, respectively) were used in the calculations. The standard incidence ratio for new malignant disease was 1.37 (confidence interval, 1.15-1.62).

CONCLUSION

Neither duration of anesthesia nor increased cumulative time with profound sevoflurane anesthesia was associated with an increased risk for new malignant disease within 5 years after surgery in previously cancer-free patients.