Survival after primary breast cancer surgery following propofol or sevoflurane general anesthesia - aretrospective, multicenter, database analysis of 6,305 Swedish patients.

BACKGROUND: Retrospective studies indicate that the choice of anesthetic can affect long-term cancer survival. Propofol seems to have an advantage over sevoflurane. However, this is questioned for breast cancer. We gathered a large cohort of breast cancer surgery patients from seven Swedish hospitals and hypothesized, that general anesthesia with propofol would be superior to sevoflurane anesthesia regarding long-term breast cancer survival. METHODS: We identified all patients who were anaesthetized for breast cancer surgery between 2006-2012. The patients were matched to the Swedish Breast Cancer Quality Register, to retrieve tumor characteristics, prognostic factors and adjuvant treatment as well as date of death. Overall survival between patients undergoing sevoflurane and propofol anesthesia were analyzed with different statistical approaches: 1) multiple Cox regression models adjusted for demographic, oncological, and multiple control variables, 2) propensity score matching on the same variables, but also including the participating centers as a cofactor in a separate analysis. RESULTS: The database analysis identified 6,305 patients. The five-year-survival rates were 91.0% and 81.8% for the propofol and sevoflurane group, respectively in the final model (P=0.126). Depending on the statistical adjustment method used, different results were obtained, from a non-significant to a "proposed" and even a "determined" difference in survival that favored propofol, with a maximum of 9.2 percentage points higher survival rate at five years (Hazard ratio 1.46, 95% CI 1.10-1.95). CONCLUSIONS: It seems that propofol may have a survival advantage compared with sevoflurane among breast cancer patients, but the inherent weaknesses of retrospective analyses were made apparent.