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.