Journal of Advances in Medicine and Medical Research

Background: The liver is the most common site of metastasis, followed by the lungs. Approximately 10% of colorectal cancer patients develop lung metastasis during the course of the disease. Colorectal cancer (CRC) ranks among the top three cancers in terms of incidence, and it accounts for 10.2% of all cancer cases worldwide.

Objectives: To investigate the association between lung metastasis and the previously mentioned risk factors in colorectal patients.

Methods: This retrospective, case-control study was conducted in the Royal Hospital, Oman. Patients in this study. Data on patient demographics, tumour characteristics, metastasis from computed tomography reports, who were diagnosed with colorectal adenocarcinoma between 2014 and 2019 were included in and histopathology features were gathered from Al Shifa system. The study sample size was calculated to a confidence interval of 95% and a minimum of 500 patients must be included. Patients were divided into two groups based on the presence/absence of lung metastasis. Patients were followed up for one year post-diagnosis to determine the progress of detected lung nodules. A statistical analysis using IBM SPSS Statistics 25 was carried out, and p < 0.050 was considered statistically significant with 95% confidence interval.

Results: A total of 523 patients were included, and the majority (57.2%) were male with a mean age of 57.8±4.02. Prevalence of lung metastasis was 17.6% (95% CI = 14.4%–21.1%). There was a significant association of lung metastasis with T3 (56.3%) and T4 (39.4%) tumours (LR = 14.348, p = 0.002). Presence of lymph-node metastasis also showed a significant association with lung metastasis (83.5%, p = 0.0001). Patients with liver metastasis at the time of diagnosis also had a higher risk of lung metastasis (60.2%, p = 0.0001). Tumours with neurovascular invasion and KRAS mutation were significantly associated with lung metastasis (p <0.050). However, there was no statistically significant association with age, gender, carcinoembryonic antigen level, and histopathology grade. Patients with KRAS mutation have a three times higher risk for lung metastasis compared to patients with WT (OR = 3.366, 95% CI = 1.220–9.288, p = 0.019).

Conclusion: Presence of KRAS mutation is the only independent predictor of lung metastasis in colorectal cancer patients. Pre-operative chest computed tomography must be done as part of the staging workup for all new patients, regardless of the previously mentioned risk factor status. The overall analysis concludes that KRAS status is the only independent predictor of lung metastasis in newly diagnosed colorectal cancer patients that can be relied on in a clinical setting to guide the use of staging chest CT.