Cancer Mortality Affected by the Choice of Anesthetic Drugs?

Knowledge gap: Does the choice of anaesthetic affect outcome for cancer surgery?

Aim: To retrospectively examine possible associations (Cox Multiple Regression) between survival from breast-, colorectal-, or skin cancer and the choice of hypnotic used during surgery, ahead of a prospective randomised controlled trial.

Hypotheses: One- and five-year survival will be significantly higher after radical breast-, colorectal-, or skin cancer surgery in patients given the intravenously administered hypnotic propofol than in patients given the inhalational hypnotic sevoflurane.

Method: To merge two registers, of which one holds demographic- anaesthetic-, and surgical data from 6 303 patients operated on at the three mentioned anatomical locations at the Central Hospital in Vasteras, Sweden during a twelve year period (1998-2009). Of these minimum 4 500 operations would be due to cancer. This register is unique, in that it contains both types of anaesthesia. The other register holds survival data (date and cause of death), stored at the Regional Oncologic Center in Uppsala.

The choice of anaesthetic will be validated by controlling each patient's anaesthetic paper file, concomitantly with extraction of details from anaesthesia and surgery, such as the functional classification of each patient (according to American Association of Anesthesiologists), co-morbidity, duration of anaesthesia and surgery, amount of blood loss and possible transfusion.

Current knowledge: Different anaesthetics have opposite effects on the immune system and on the DNA. There is a well-established association between the state of the immune system and cancer growth, which in turn will influence survival. There is also an association between DNA damage and cancer development. Inhalational anaesthetics, e.g. sevoflurane, act pro-inflammatory, and they are also proven to be genotoxic. Propofol is anti-inflammatory and anti-oxidative, and it is not genotoxic.

Objective: Strengthen the hypotheses, and get statistics for a proper power calculation in advance of a multi-centre, prospective, randomised, controlled trial.

Impact: General anaesthesia is an indispensable part of radical cancer surgery. Undesired effects from anaesthesia on survival has strong relevance for the over all cancer treatment.