Overall, ALCAM and ALDH1 in this limited patient cohort exhibited elevated serum levels compared with healthy controls, and tumor tissues demonstrated stage-dependent increases in marker expression (UICC III/IV versus I/II).<h4>Conclusions</h4>Serum concentrations of ALCAM and ALDH1 were significantly elevated in our patient cohort with rectal cancer but showed no significant correlation with tumor stage or survival, whenever serum samples were obtained either during or after neoadjuvant and adjuvant therapy, which may be particularly due to the limited number of studied subjects. Here, ALDH1A1 is linked to rectal cancer.