Patient Selection:
• Patients with gastric or colorectal adenocarcinomas who had potentially curative surgery (removal of primary tumor and all intraperitoneal metastases, with no residual gross intra-abdominal tumor).
• Most patients underwent chemotherapy post-operatively.
• Serial CEA monitoring was performed every 1-2 months after initial treatment. A baseline was established, with recurrence often associated with an increase in CEA concentrations above that baseline.
• Not all patients with recurrent adenocarcinoma showed an increase in CEA levels. These patients would not be included in the evaluation.
CEA:
• upper limit of reference range was 5 ng/mL
• adjustment for smokers (who may have CEA levels in 5.1 to 10 ng/mL range without tumor) was not made
• 4 or 5 consecutively increasing CEA values used for reliable calculation of the doubling time.
• a regression line was drawn through the plot of (days from initial CEA increase) as the x axis, versus LOG10 (CEA level) on the y-axis
LOG10 (CEA) =
= ((slope) * (days after initial CEA increase)) + (intercept)
Since
CEA =
= 10 ^ (((slope) * (days after initial CEA increase)) + (intercept))
and the (days after initial CEA increase) = 0 for initial CEA increase,
CEA doubling time from initial CEA increase =
= LOG10(2) / (slope of the regression line)
Survival
The length of the CEA doubling time correlated with survival (with both gastric and colorectal carcinomas considered together):
• for CEA doubling time < 40 days, mean survival was 150 days
• for CEA doubling time of 40-126 days, mean survival was 398 days
• for CEA doubling time of > 126 days, mean survival was 644 days
• for a given CEA doubling time, patients with recurrent colorectal carcinomas tended to have a longer survival than those with recurrent gastric carcinomas
For patients with gastric carcinoma who underwent surgery and chemotherapy:
LOG10 (survival after initial CEA increase in days) =
= (0.367 * (LOG10 (CEA doubling time in days))) + 1.789
For patients with colorectal carcinoma who underwent surgery and chemotherapy:
LOG10 (survival after initial CEA increase in days) =
= (0.831 * (LOG10 (CEA doubling time in days))) + 0.971
Additional Associations
Flow cytometric analysis showed that tumors with a high percentage of cells in S phase (>= 15%) had a significantly shorter CEA doubling time than those with a low percentage (< 15%).
