Regional anesthesia prevents cancer recurrence after oncosurgery! What is wrong with the hypothesis?

Several studies have investigated the hypothesis of the efficacy of regional anesthesia (RA) techniques in preventing cancer recurrence when used perioperatively during oncological surgeries. Although theoretically, the association appears beneficial, the patient outcomes after cancer surgeries with or without RA were comparable, that is, the use of RA did not improve patient survival or prevent cancer recurrence after surgery. Another problem with this data is its retrospective nature which makes its interpretation difficult. Moreover, there are a lot of other confounding factors like comorbidities, tumor biology, nosocomial infections, duration of hospital stay, and baseline immunity, which is not comparable, and hence make standardization for a well-designed prospective study difficult. Return to intended oncologic therapy (RIOT) involves treatment in the form of radiation or chemotherapy which, if received on time after the planned oncosurgery, could provide a better chance of preventing cancer recurrence and improved survival. However, none of the retrospective studies have correlated cancer recurrence with delay in RIOT or not receiving RIOT as a cause of cancer recurrence. This paper discusses why even a well-designed, prospective trial could possibly never establish the efficacy of RA in preventing cancer recurrence and improving survival due to the complexities involved in a patient undergoing oncosurgery.