 Regarding sample size for repeated measures quality of life data, common practice is to pick a single time point and calculate sample based on a single difference in group means, inflating sample size for dropout. This gives a conservative estimate of sample size in most cases. This is the approach adopted here, as although sample size calculations based on repeated measures models can be more accurate, in this case this approach is unlikely to provide more accuracy, given uncertainties as to the final group sizes for this observational study. The investigators assume that there will be maximal quality of life difference at 6 months and expect on the basis of clinical estimates that the ratio of group sizes for very extensive v standard surgery of 2:1. The investigators have assumed p.05 and power of 80. It has been suggested that an evidence based medium difference in the EORTC QLC 30 is 13 points. The mean score in stage II-IV ovarian cancer patients at baseline in the EORTC scoring manual is 56.3 SD 24.5, while six month follow-up scores in a trial of neo-adjuvant versus primary de-bulking surgery was 73.1 SD3.0 at six months in the primary surgery arm n201. The difference in Standard deviations may reflect the tight inclusion criteria for a randomised trial, and it might be assumed that in this observational study of surgical candidates would fall somewhere between the two figures. Assuming that QLC 30 at six months may be lower than this average those undergoing very extensive surgery at 66, but that the standard deviation is as reported in the scoring manual at 24 likely to be a conservative assumption and that a 13 point difference would be of clinical importance, a sample size of 123 group 141 and group 282 would be required, with additional allowance for dropout or a comparable SD to that reported in the scoring manual 10 to 20 patients calculations made in Stata 13.1. 