[Prediction of recurrence of gastrointestinal cancer from standpoint of biological malignancies--tumor marker doubling time and its a half life period line].

It is well generally accepted that several tumor markers may be useful for determination of staging, metastatic patterns, devices of the malignancy and prediction of recurrence in postoperative follow-up. Our analysis of tumor markers in gastrointestinal cancer indicated that the patients who had a high level of AFP in the serum of gastric cancer patients showed a correlation between preoperative AFP level and liver metastasis. In patients with carcinomatous peritonitis positive rate of CA125 level in serum was 42.9% and, more importantly, the elevation of CA125 level after surgery was observed in 72.2% of patients complicated peritoneal dissemination before clinical evidence. On the other hand, the change of tumor marker levels in serum after surgery were plotted on a semi-logarithmic scale and we monitored tumor marker changes until the level decrease to the normal range or when recurrence was detected on imaging diagnosis. All patients showing high levels of CEA had surgical resection for gastrointestinal cancers. In the group of 25 patients who had no recurrence within 1 year or more, CEA levels decreased exponentially until these reached the normal range. The half life period of CEA was 4 to 5 days. However, CEA levels in 13 of 19 patients who recurred showed a dissociation from the theoretical line of half life period before the level decreased to normal range. We interpreted that this dissociation was caused by the growth of residual cancer cells. In other word, if dissociation point from exponential decrease line of CEA were pointed after the surgery, we can predict a possibility of recurrence in earlier period after surgery.