Serum ferritin and the risk of early-onset colorectal cancer

Table 2 Early-onset colorectal cancer vs healthy controls stratified by age, sex, and serum ferritin

	EO-CRC	Healthy controls	P value
Female: Age 29-39			Fisher’s exact: P = 0.029
Ferritin ≤ 20.0 ng/mL	13/20 (65.0%)	10931/34035 (32.1%)	0.002
20.1-45.0 ng/mL	3/20 (15.0%)	10626/34035 (31.2%)	0.116
45.1-100.0 ng/mL	2/20 (10.0%)	8039/34035 (23.6%)	0.153
≥ 100.1 ng/mL	2/20 (10.0%)	4439/34035 (13.0%)	0.689
Male: Age 29-39			Fisher’s exact: P = 0.0098
Ferritin ≤ 20.0 ng/mL	4/10 (40.0%)	423/5892 (7.2%)	< 0.00001
20.1-45.0 ng/mL	1/10 (10.0%)	825/5892 (14.0%)	0.719
45.1-100.0 ng/mL	1/10 (10.0%)	1738/5892 (29.5%)	0.177
≥ 100.1 ng/mL	4/10 (40.0%)	2906/5892 (49.3%)	0.555
Female: Age 40-49			Fisher’s exact: P = 0.456
Ferritin ≤ 20.0 ng/mL	11/28 (39.3%)	9364/32750 (28.6%)	0.211
20.1-45.0 ng/mL	8/28 (28.6%)	9947/32750 (30.4%)	0.834
45.1-100.0 ng/mL	4/28 (14.3%)	8230/32750 (25.1%)	0.187
≥ 100.1 ng/mL	5/28 (17.9%)	5209/32750 (15.9%)	0.779
Male: Age 40-49			Fisher’s exact: P < 0.00001
Ferritin ≤ 20.0 ng/mL	10/26 (38.5%)	519/7534 (6.9%)	< 0.00001
20.1-45.0 ng/mL	3/26 (11.5%)	920/7534 (12.2%)	0.920
45.1-100.0 ng/mL	4/26 (15.4%)	2021/7534 (26.8%)	0.187
≥ 100.1 ng/mL	9/26 (34.6%)	4074/7534 (54.1%)	0.047

For the purpose of this analysis, one patient in early-onset colorectal cancer (EO-CRC) cohort, age 22 years, was excluded to limit biases. Fisher’s exact test was used to compare the proportions of the different serum ferritin level groups between EO-CRC and healthy controls (HCs). Then post-hoc z-test of proportions were used to compare specific serum ferritin levels between EO-CRC and HCs. Patients were grouped by age and sex to minimize confounding factors.