within the almost linear part of the survival curve). with a survival curve approaching linearity), the other to distinguish between patients with intermediate SPF values and those with high values (i.e. within the parabolic survival curve) from those with higher values (i.e.
An alternative procedure might be to use two cut-off levels, one to distinguish patients with the lowest SPF values (i.e. The non-linearity of the curves is incompatible with the general use of the median SPF as a prognostic cut-off value. Furthermore, both disease-free survival and the relative risk of recurrence exhibited a non-linear relationship with SPF values the curves implied that the prognosis was better among patients with SPF values about 2-5% than in patients with lower SPF values (parabolic shape), though the relationship with higher SPF values approached linearity.
Using different survival end-points and chi 2 values for each cut-off level, two optimal cut-off points, at the 7% and 12% levels, were consistently obtained for the SPF. Clinically, all patients were without distant spread at the time of diagnosis, and the median duration of follow-up was 4 years. It was possible to evaluate the SPF in 566 (94%) of 603 consecutive cases where fresh frozen specimens were available in a tumour bank at our department. Here we report findings from a study of primary breast cancer, showing how the prognostic value of the fraction of cells in the S-phase of the cell cycle (SPF), as measured by flow cytometry, can be affected by the SPF cut-off level(s) adopted. The use of continuous prognostic variables is clinically impractical, and arbitrarily chosen cut-off points can result in a loss of prognostic information.
0 kommentar(er)
