 Several observational studies and two systematic reviews of non-randomised studies have shown an association between the amount of residual disease following surgery and survival, controlling for various confounding factors. However, the systematic reviews identified no randomised control trials directly comparing standard surgery versus extensive surgery. A National Institute for Health and Care Excellence NICE Interventional Procedures Overview found a number of retrospective observational studies comparing extensive with standard surgery, and found that women who underwent extensive surgery had better survival to those undergoing standard surgery, thus suggesting that the utilisation of surgical procedures to achieve complete cytoreduction may overcome disease aggressiveness. Incidence of serious complications, however, was higher in patients undergoing extensive surgery. However, there were several confounding factors e.g patients with good performance status are more likely to be selected to undergo extensive surgery. Equally, patients with lesser disease burden can have complete removal of tumour by standard surgery alone. 