This study is a prospective, randomized, double-blind, phase II interventional clinical trial evaluating the effect of perioperative intravenous lidocaine infusion compared with high-dose dexamethasone on postoperative immune response and clinical outcomes in patients undergoing surgery for colon cancer. Patients with colon cancer often experience postoperative inflammatory and immune changes that may influence recovery and complications. The aim of this study is to assess whether perioperative lidocaine infusion may improve postoperative immune function and clinical recovery compared with standard perioperative anti-inflammatory treatment. Participants will be randomly assigned to receive either intravenous lidocaine infusion or high-dose dexamethasone during the perioperative period. Immune response markers and postoperative clinical outcomes will be evaluated. The results of this trial may contribute to improved perioperative management and recovery strategies for patients undergoing surgery for colon cancer.

This study is a prospective, randomized, double-blind, controlled phase II interventional clinical trial conducted at the Institute of Oncology Ljubljana. The trial investigates the effects of two perioperative pharmacological interventions-intravenous lidocaine infusion and high-dose dexamethasone-on postoperative immune response and clinical outcomes in patients undergoing surgical treatment for colon cancer.

Patients undergoing major oncologic surgery may develop significant perioperative immune suppression and inflammatory responses, which can influence postoperative recovery, complication rates, and overall outcomes. Lidocaine is known to have potential anti-inflammatory and immunomodulatory effects, while dexamethasone is widely used perioperatively for its anti-inflammatory properties. However, comparative evidence regarding their impact on postoperative immune response in colorectal cancer surgery is limited.

Eligible participants are adult patients with histologically confirmed colon cancer who are scheduled for surgical resection. After providing written informed consent, participants will be randomized in a double-blind manner to one of two study groups:

Perioperative intravenous lidocaine infusion group

High-dose perioperative dexamethasone group

Both interventions are administered according to the study protocol during the perioperative period. Randomization and masking ensure that participants, investigators, and clinical staff remain blinded to treatment allocation.

The primary objective of the study is to evaluate differences in postoperative immune response between the two intervention arms, assessed through laboratory immune and inflammatory markers. Secondary objectives include evaluation of postoperative clinical outcomes, such as postoperative recovery parameters and complications.

Participants are followed during the perioperative period and after surgery, and study assessments are performed according to the predefined schedule. This study will provide evidence regarding whether perioperative lidocaine infusion may offer beneficial immunological or clinical effects compared with high-dose dexamethasone in patients undergoing surgery for colon cancer. The results may support improved perioperative supportive care strategies and optimization of postoperative recovery in oncologic surgical patients.

Inclusion Criteria:

• Adult patients aged 18 years or older
• Histologically confirmed colon cancer
• Scheduled for elective surgical resection of colon cancer
• Eligible for perioperative treatment with study medication (lidocaine, dexamethasone, or placebo) according to the protocol
• Ability to understand the study procedures and provide written informed consent

Exclusion Criteria:

• Known allergy or hypersensitivity to lidocaine, dexamethasone, or any excipients
• Severe hepatic impairment
• Severe renal impairment
• Severe cardiac conduction disorders or clinically significant arrhythmias
• Pregnancy or breastfeeding
• Severe uncontrolled comorbidities that could interfere with study participation
• Participation in another interventional clinical trial that could influence study outcomes
• Any other condition which, in the opinion of the investigator, makes the patient unsuitable for participation

Double-blind design: participants, care providers, investigators, and outcome assessors are blinded to treatment allocation. Study medication is prepared and labeled in an identical manner to maintain blinding.