Tumour markers
Using the same methodology for age, we investigated the hypothesis of
the existence of a threshold in the relationship between serum AFP
levels at diagnosis and outcome. The analysis suggested negligible or no
effect of serum AFP levels on OS or EFS for (relatively) small values of
AFP, but a rapid increase of the hazard ratio for high values (note that
both the horizontal and vertical scales are logarithmic). Serum AFP
levels became significant as a prognostic factor for outcome at a serum
AFP level ≈ 33,000 ng/ml for OS (Fig. 5) and a serum AFP level ≈ 21,600
ng/ml for EFS (p=0.044) (Fig. 6) (using the point where the 95% CI
crossed the relative hazard ratio equal to one).