Cumulated time with low bispectral index values is not related to the risk of new cancer or death within 5 years after surgery in patients with previous or prevailing malignancy.

Background: Preclinical data indicate that anesthesia and surgery may promote cancer growth. We previously found no increased risk of malignant disease within 5 years regarding duration of general anesthesia (TANESTH) and time with Bispectral Index (BIS) under 45 (TBIS < 45) in patients without any diagnosis or history of malignancy before or within 1 month after surgery. Because immunocompetence may be different in patients with previous malignant disease, we investigated the corresponding risk in patients with earlier or existing malignant disease at the time of surgery.

Methods: In a prospective cohort of 766 BIS-monitored patients anesthetized with sevoflurane, new malignant diagnoses and death within 5 years after surgery were retrieved. Cox regression was used to assess the risk of new cancer and all-cause death during follow-up in relation to (TANESTH) and (TBIS <45).

Result: Fifty-one patients (6.7%) were assigned 54 new malignant diagnoses within 5 years after surgery. Cancer surgery comprised 387 (51%) of the index operations. Two hundred ninety-three (38 %) of the patients died during follow-up. No relation between TANESTH or TBIS <45 and new malignant disease (hazard ratio [HR] 0.64-1.11 and 0.76-1.30, respectively) or death was found (HR 0.85-1.05 and 0.94-1.16, respectively). Nor were any corresponding significant relations obtained when other thresholds for BIS (i.e., < 30, 40, and 50, respectively) were investigated.

Conclusion: In patients with previous or existing malignant disease, neither duration of anesthesia nor increased cumulative time with profound sevoflurane anesthesia was associated with an increased risk for new cancer or death within 5 years after surgery. Monitoring "depth of anesthesia" is not expected to alter the risk of cancer proliferation after surgery.