Time-dependent relevance of prognostic factors in patients with gastric cancer.

Background/aims: Prognostic factors are useful for establishing a prognosis of patients from the time of operation. However, the value of individual prognostic factors may change dependent on the length of the follow-up period, and it is not clear how long these factors keep their prognostic relevance.

Methodology: Data was used from 233 Japanese patients treated by potentially curative resection for primary gastric cancer, between 1993 and 1998. Survival analysis was done starting at 1-yearly intervals after operation and follow-up in the first analysis started at the time of the operation.

Results: Prognostic relevance of tumor size was not evident for total follow-up time but was significantly emphasized 1 year after operation. Serosal invasion lost its prognostic value within one year of operation. The status of lymph node metastases retained its ability to predict survival after 2 years' follow-up whereas after 3 years' follow-up nodal status seemed to be without significance.

Conclusions: A distinct time-dependency with varied patterns was found in the influence of some prognostic factors on survival. Detecting the changing importance of prognostic factors could provide new biological insights that might otherwise be missed, and may help determine the most appropriate clinical use of various factors.