Learning curve
Based on significant predictors in univariate logistic regression, multivariate risk models were fitted. The final multivariate risk model used for RA-CUSUM analysis included age (odds ratio = 1.03, 95% CI 1.00-1.06, p=0.03) and adjuvant or adjusted treatment (odds ratio = 3.15, 95%CI 1.41-7.04, p=0.01), which summarises multiple prognostic factors significant at univariate analysis (e.g. lymph node status, LVSI and tumour size). Adjusted treatment was defined as replacing radical hysterectomy with chemoradiation because of an intraoperative finding of positive lymph node at frozen section.
Figure 1 shows the expanded RA-CUSUM charts. From the introduction of the novice surgeon (group 3) no new peak in RA-CUSUM+ chart is observed and the chart moves around zero, indicating satisfactory results with regard to the observed recurrence rate. The RA-CUSUM- chart, indicating further improvement of surgical performance by moving more negatively, has stabilized in group 3 and does not show further improvement.