Retroperitoneal soft tissue sarcoma: Margins. R D(t) of extension of resection margins estimated using different methods. PV identity: estimated effect using pseudo values, identity link and interaction between time and margins. Five pseudo times were used at times 6, 11, 23, 51, 96, corresponding to quantiles 10%, 25%, 50%, 75%, 90% of the failure time distribution. CGPM: Corrected group prognosis method using a proportional hazard Cox regression model. The averaging is performed on the whole sample of patients. Other two measures are reported: (1) average over exposed: obtained averaging only on patients with macroscopic resection margins (E I N(t)); (2) average over unexposed: obtained averaging only on patients without microscopic resection margins (N N E(t)).