Risk model and sensitivity analysis
In order to determine the learning curve with RA-CUSUM multiple risk models, obtained with logistic regression, were tested. The first risk of recurrence model containing three independent variables – age, parametrial involvement and lymph node status – was overall significant (P = 0.009). However, only age and lymph node status were unique significant variables (OR 1.05 (CI 1.01-1.09) and OR 4.23 (CI 1.32-13.57), respectively). Due to the majority of patients being staged IB1, FIGO stage was not included. When replacing parametrial involvement and lymph node status with adjuvant or adjusted treatment, which summarises multiple prognostic factors, this variable yielded a more significant risk model (P = 0.001) and a strong association to recurrent disease (OR = 3.85 (CI 1.46 – 10.16)). The final model used for the RA-CUSUM chart (below) included age and adjuvant or adjusted treatment. Outcomes of the RA-CUSUM did not change substantially for the various models.