Background: Colorectal cancer is the second most common type of cancer and a leading cause of cancer-related deaths worldwide. Approximately 15% of the patients with colorectal cancer will already have liver metastases (CRLMs) at diagnosis. Luckily, the advances in chemotherapy regimens during the past few decades have led to increased rates of disease regression that could even render an originally unresectable disease resectable. In certain patients with CRLMs, the hepatic lesions are missing on preoperative imaging after neoadjuvant chemotherapy. These patients can undergo surgery with or without resection of the sites of the disappearing liver metastases (DLMs). In this systematic review, we assess the recurrence rate of the DLMs that were left unresected as well as the complete pathologic response of those resected. Methods: A literature search was conducted in PubMed for studies including patients with CRLMs who received neoadjuvant chemotherapy and had DLMs in preoperative imaging. Two independent reviewers completed the search according to the PRISMA checklist. Results: Three hundred and twenty-six patients with 1134 DLMs were included in our review. A total of 47 out of 480 DLMs (72.29%) that were removed had viable tumor cells in postoperative histology. One hundred and forty-five tumors could not be identified intraoperatively and were removed based on previous imaging, with thirty (20.69%) of them presenting viable cancer cells. Four hundred and sixty-five lesions could not be identified and were left in place. Of them, 152 (32.69%) developed local recurrence within 5 years. Of note, 34 DLMs could not be categorized as viable or non-viable tumors. Finally, DLMs that were identifiable intraoperatively had a higher possibility of viable tumors compared to non-identifiable ones (72.29% vs. 20.69%, respectively). Conclusions: Disappearing liver metastases that are left unresected have an increased possibility of recurrence. Patients receiving neoadjuvant treatment for CRLMs may have better survival chances after resecting all the DLM sites, either identifiable intraoperatively or not.

Background/Objectives: Colorectal cancer (CRC) is among the most commonly reported malignancies globally, taking the third place in incidence among males as well as the second among females, with over 1.9 million new cases and 935,000 deaths estimated worldwide in 2020. One of the most common and clinically significant comorbidities in patients undergoing CRC surgery is preoperative anemia, with reported prevalence ranging from 23% to over 60% depending on the population and diagnostic criteria used. The objective of the current study is to systematically evaluate the current body of evidence on preoperative anemia management in adults undergoing surgery for non-metastatic CRC. This review aims to assess the clinical impact of different iron supplementation strategies, particularly IV versus oral iron in pre-operative hematologic optimization, transfusion requirements, postoperative complications, and recovery outcomes. Methods: The current systematic review was conducted based on the PRISMA for Systematic Reviews and Meta-analysis checklist. The study has been registered to PROSPERO with the ID CRD420251113455. Results: Across all studies, IV iron and erythropoiesis-stimulating agents emerged as safe and more efficient alternatives to iron per os, especially when initiated at least two weeks before surgery. Thus, highlighting the clinical value of proactive anemia management as a cornerstone of surgical prehabilitation, potentially reducing transfusion burden and improving recovery outcomes for CRC patients. Conclusions: It is observed that IV iron therapy offers a more effective strategy than per os supplementation for correcting preoperative anemia in non-metastatic colorectal cancer patients. Their hematologic benefits enhance surgical readiness and reduce postoperative intervention needs. Thus, supporting the integration of IV iron into preoperative optimization protocols.

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Colorectal cancer (CRC) remains one of the most frequently diagnosed malignancies worldwide and a leading indication for major abdominal surgery, with a rising incidence among younger adults. Because CRC resection is a physiologically demanding procedure performed in a frequently comorbid, often anemic and malnourished population, the preoperative period represents a decisive window in which laboratory and diagnostic testing shapes staging, risk stratification, and optimization. This narrative review is deliberately confined to the preoperative window—from histological diagnosis to the day of elective, curative-intent colon or rectal resection—and synthesizes evidence retrieved from PubMed/MEDLINE, Scopus, and ScienceDirect together with current society guidelines. It is organized around four themes: (i) the core laboratory workup, including the complete blood count and preoperative anemia, iron studies, metabolic and hepatic panels, coagulation testing, and carcinoembryonic antigen (CEA); (ii) the diagnostic and staging workup, encompassing complete colonic evaluation, contrast-enhanced computed tomography, pelvic magnetic resonance imaging for rectal cancer, and the selective role of positron emission tomography; (iii) risk stratification and preoperative optimization, spanning patient blood management, nutritional assessment and albumin, computed-tomography-defined low skeletal muscle mass, frailty, functional capacity, prehabilitation, and glycemic control; and (iv) molecular characterization, distinguishing mismatch-repair/microsatellite-instability (MMR/MSI) testing—an established, widely recommended component of CRC evaluation—from genuinely emerging biomarkers such as circulating tumor DNA (ctDNA) and systemic inflammatory and prognostic nutritional indices. Differences between colon and rectal cancer, elective and emergency presentation, and upfront versus post-neoadjuvant surgery are signposted throughout. We further integrate these elements within contemporary guideline and Enhanced Recovery After Surgery (ERAS) frameworks, including the 2025 ERAS Society recommendations for elective colorectal surgery, and distill them into a practical, evidence-based preoperative checklist specifying thresholds, timing, interventions, and strength of supporting evidence. We emphasize that the prognostic power of postoperative ctDNA does not yet translate into ctDNA-guided treatment decisions outside clinical trials. The central message is that preoperative testing in CRC should be purposeful and stage- and risk-adapted rather than reflexive: each investigation should refine staging, modify perioperative management, or enable measurable optimization. Each risk domain is paired with the intervention it should trigger, the criteria identifying candidates for extended thromboprophylaxis are specified, and the systemic inflammatory indices are framed as a trigger for optimization rather than as prognostic commentary.