[The importance of completing a follow-up--its influence on survival curves].

We studied the influence of levels of follow-up (F/U) on survival curves in 100 patients with tongue cancer. The levels were defined according to the methods of F/U, such as chart review, direct contact with the patients or family, etc. Consequently, complete F/U data were obtained for all but one patient, who was missed after a 15-year period of no evidence of disease. The more complete the F/U data were, the lower the survival figures, however, the disease-specific survival figures were increased. The relapse-free rates were not changed with completing F/U. The P-values of the generalized Wilcoxon test and long-rank test rose with an increase of F/U levels.