Univariate and multivariate Cox proportional hazard models.

The sensitive and intermediate RI groups were merged into a common non-resistant group of patients. The redefined non-resistant (RI 0–75%) and resistant (RI 75–100%) groups were analysed by univariate (P-value  = 0.003 for PFS and P-value  = 0.00089 for OS) as well as a multivariate Cox proportional hazard models documenting an association with PFS and OS (P-value of 0.0063 and 0.0025), independent of age, sex and ISS staging. The appropriateness of the Cox proportional hazard models using the dichotomized resistance index was checked using cumulative martingale residuals.