Timeliness of postoperative serum carcinoembryonic antigen monitoring for predicting recurrence after gastric cancer surgery

Table 1 Criteria for recurrence and case distribution

Criterion for recurrence	Number of cases (n)	Percentage (%)
Imaging (CT or PET/CT) revealing new masses within the primary surgical field	15	38.5
Imaging (CT or PET/CT) detecting space-occupying lesions in other organs (distant metastasis), with primary tumors excluded	12	30.8
Confirmation of recurrence via gastroscopy and pathological biopsy (local recurrence)	8	20.5
Confirmation of recurrence through reoperation or exploratory surgery	2	5.1
Presence of uncontrollable hemorrhagic ascites, or detection of cancer cells in ascites cytology (peritoneal carcinomatosis)	2	5.1
Total	39	100

CT: Computed tomography; PET: Positron emission tomography.

Table 2 Comparison of baseline clinical characteristics between groups

Items		Recurrence group (n = 39)	Non-recurrence group (n = 81)	t/χ2	P value
Sex	Male	21 (53.85)	47 (58.02)	0.826	0.106
	Female	18 (46.15)	32 (41.98)
Age (years)		59.48 ± 4.09	59.29 ± 4.11	0.883	0.217
Pathological staging	I	12 (30.77)	22 (27.16)	0.907	0.114
	II	20 (51.28)	47 (58.02)
	IIIa	7 (17.95)	12 (14.81)
Differentiation	Low differentiation	23 (58.97)	46 (56.79)	0.746	0.083
	Medium differentiation	15 (38.46)	31 (38.27)
	High differentiation	1 (2.57)	4 (4.94)
BMI (kg/m2)		20.16 ± 0.68	20.23 ± 0.73	0.842	0.103

Continuous data are presented as mean ± SD and compared by independent t-test. Categorical data are presented as n (%) and compared by χ² test, except where expected cell counts were below 5, in which case Fisher's exact test was used. BMI: Body mass index.

Table 3 Comparison of preoperative and postoperative serum carcinoembryonic antigen, alpha-fetoprotein, and carbohydrate antigen 19-9 levels between groups

Group	CEA (ng/mL)			CA19-9 (U/mL)			AFP (μg/L)
	Post-1 week	Post-3 months	Post-6 months	Post-1 week	Post-3 months	Post-6 months	Post-1 week	Post-3 months	Post-6 months
Recurrence group (n = 39)	16.11 ± 3.18	25.23 ± 4.08a	29.12 ± 4.26a,b	26.34 ± 5.17	29.19 ± 5.08a	35.27 ± 4.16a,b	20.13 ± 3.27	24.29 ± 3.18a	27.15 ± 3.41a,b
Non-recurrence group (n = 81)	16.09 ± 3.22	19.12 ± 3.18a	21.11 ± 4.17a,b	26.24 ± 5.17	22.47 ± 5.15a	26.08 ± 3.86a,b	20.09 ± 3.23	22.21 ± 3.32a	24.32 ± 3.41a
t value	0.322	9.317	10.441	0.989	7.297	12.576	0.063	3.416	4.298
P value	0.064	0.000	0.000	0.103	< 0.01	0.000	0.074	0.000	0.001

^aP < 0.05 vs the same group at one week postoperatively.

^bP < 0.05 vs three months postoperatively.

CEA: Carcinoembryonic antigen; AFP: Alpha-fetoprotein; CA19-9: Carbohydrate antigen 19-9.

Table 4 Logistic regression analysis of postoperative recurrence in gastric cancer

Independent variable	Coefficient of regression	SE	β	P value	OR (95%CI)
CEA	0.427	0.221	0.315	0.001	1.318 (0.787-4.846)
AFP	0.245	0.143	0.127	0.010	1.327 (1.304-2.132)
CA19-9	0.337	0.371	0.135	0.074	0.414 (0.126-0.627)

CEA: Carcinoembryonic antigen; AFP: Alpha-fetoprotein; CA19-9: Carbohydrate antigen 19-9; OR: Odds ratio; 95%CI: 95% confidence interval.

Table 5 Correlation between carcinoembryonic antigen, alpha-fetoprotein, and carbohydrate antigen 19-9 and time to recurrence following gastric cancer surgery

Items		CEA	AFP	CA19-9
Time of postoperative recurrence	r value	-0.634	-0.603	-0.589
	P value	0.001	< 0.001	0.001

CEA: Carcinoembryonic antigen; AFP: Alpha-fetoprotein; CA19-9: Carbohydrate antigen 19-9.

Table 6 Predictive value of serum carcinoembryonic antigen and alpha-fetoprotein for postoperative recurrence of gastric cancer

Variable	AUC	95%CI	Youden index	P value	Specificity (%)	Sensitivity (%)
CEA	0.702	0.608-0.783	0.55	0.001	68.11	81.09
AFP	0.688	0.514-0.732	0.62	0.001	45.20	80.52
Combination of the two	0.826	0.702-0.878	0.69	0.001	94.36	90.50

CEA: Carcinoembryonic antigen; AFP: Alpha-fetoprotein; 95%CI: 95% confidence interval; AUC: Areas under the receiver operating characteristic curve.