Retroperitoneal soft tissue sarcoma: Grading. The effect of the different Grading categories on the R R(t) and R D(t) scales are reported, using different estimation methods. CGPM applied to a proportional hazard Cox model; PV with log and identiy links and interaction between time and grading. The estimates obtained with the different techniques appears quite in agreement. No evidence for time dependent effects in the Cox model was found.