Serum ferritin and the risk of early-onset colorectal cancer.

Background: The incidence of early-onset colorectal cancer (EO-CRC) is rising in the United States, and is often diagnosed at advanced stages. Low serum ferritin is often incidentally discovered in young adults, however, the indication for endoscopy in EO-CRC is unclear.

Aim: To compare serum ferritin between patients with EO-CRC and healthy controls (HCs), and examine the association of serum ferritin in EO-CRC with patient- and disease-specific characteristics.

Methods: A retrospective study of patients < 50 years with newly-diagnosed EO-CRC was conducted from 1/2013-12/2023. Patients were included if serum ferritin was measured within 2 years prior to 1 year following CRC histologic diagnosis. To supplement the analysis, a cohort of HCs meeting similar inclusion and exclusion criteria were identified for comparison. A sensitivity analysis including only patients with serum ferritin obtained at or before diagnosis was separately performed to minimize risk of confounding.

Results: Among 85 patients identified with EO-CRC (48 females), the median serum ferritin level was 26 ng/mL (range < 1-2759 ng/mL). Compared to HCs (n = 80211), there were a higher proportion of individuals with EO-CRC with serum ferritin < 20 ng/mL (female 65%, male 40%) versus HCs (female 32.1%, male 7.2%) age 29-39 years (P = 0.002 and P < 0.00001, respectively). Stage IV disease was associated with significantly higher serum ferritin compared to less advanced stages (P < 0.001). Serum ferritin obtained before or at the time of diagnosis was lower than levels obtained after diagnosis. Similar findings were confirmed in the sensitivity analysis.

Conclusion: Severe iron deficiency may indicate an increased risk of EO-CRC, particularly at earlier stages. Further studies defining the optimal serum ferritin threshold and routine incorporation of serum ferritin in screening algorithms is essential to develop more effective screening strategies for EO-CRC.