Purpose: Little is known about predictable clinical factors associated with the occurrence of malignant large bowel obstruction (MLBO) in incurable stage IV colorectal cancer (CRC) patients undergoing medical treatment. This study investigates the clinical characteristics associated with MLBO that occurred while patients with stage IV CRC were receiving chemotherapy. Methods: A total of 216 patients who were diagnosed with stage IV CRC without bowel obstruction and who received chemotherapy between May 2005 and June 2012 were retrospectively included in this study. Patients were divided into an “obstruction group” and a “non-obstruction group” based on whether they did or did not develop MLBO during chemotherapy or follow-up, respectively. The initial endoscopic findings and clinical information were retrospectively reviewed and compared between the two groups. Results: Forty-six patients (21.3 %) developed MLBO during the treatment or follow-up periods. The mean duration between diagnosis and MLBO was 9.8 ± 9.3 months. After adjusting for clinically relevant factors, MLBO development was independently associated with the following factors: higher initial tumor-occupying circumference (HR 1.030 [95 % CI, 1.012–1.049], P = 0.001), longer initial horizontal tumor width (HR 1.035 [95 % CI, 1.011–1.059], P = 0.004), primary tumor location at a turning point in the colon (HR 2.404 [95 % CI, 1.185–4.877], P = 0.015), and the presence of primary tumor ulceration at presentation (HR 3.767 [95 % CI, 1.882–7.538], P < 0.001). MLBO development was not associated with tumor response to chemotherapy. Conclusion: In patients with stage IV CRC, MLBO development during chemotherapy treatment is associated with tumor ulceration, location, circumference, and width at diagnosis.
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