Therefore, considerable efforts have been made to investigate risk factors linked to distant metastasis in colorectal cancer, as well as to develop strategies for its prevention and management to improve oncological outcomes. Systemic inflammation has been identified as a key factor affecting the prognosis of colorectal cancer, prompting extensive research into various biomarkers [4–7]. Inflammatory indicators, such as the Glasgow Prognostic Score, neutrophil to lymphocyte ratio, and lymphocyte to monocyte ratio, have been extensively studied [6, 7]. More recently, the C-reactive protein to albumin ratio (CAR) has been reported to be a useful predictor of the prognosis of CRC.

Kataoka et al. [8] found a distinct association between CAR on postoperative day (POD) 7 and prognosis. They proposed that CAR on POD 7 plays a significant role in the metastatic process of cancer. Even when patients undergo scheduled adjuvant chemotherapy after surgery based on the TNM stage, recurrence is still a possibility. The CAR may be indicative of postoperative inflammation triggered by remaining tumor cells. These tumor cells experience the epithelial-mesenchymal transition, eventually detaching from the primary tumor and entering the circulatory system via neovascularization [9]. These circulating tumor cells are believed to be the main culprits for tumor dissemination through the bloodstream [10], and surgical stress can promote this hematogenous spread.

Postoperative complications can weaken the immune system and trigger a systemic inflammatory response, which can negatively impact the long-term oncological outcomes of various malignancies. Interestingly, in this study, CAR on POD 7 was independently associated with the prognosis, regardless of postoperative complications. It was not possible, however, to ascertain the mechanism by which CAR is associated with long-term oncologic outcomes [8]. There is compelling speculation that immunological markers, which are associated with the systemic inflammatory response, may be linked to cancer prognosis, as observed in clinical settings. The challenge we face now is to provide evidence that this association is not simply coincidental or a random observation. While the exact relationship between the CAR on POD 7 and long-term survival rates remains uncertain, future research should focus on developing more effective postoperative strategies and treatments for CRC.