Prognostic significance of the retroperitoneal surgical resection margin on computed tomography colonography in retroperitonealized colon cancer.

Background: A positive pathologic retroperitoneal surgical resection margin in the retroperitonealized colon is reported to predict distant metastases. However, no studies have investigated retroperitoneal surgical resection margin positivity on computed tomography colonography and its prognostic significance.

Methods: Patients who underwent primary resection for ascending or descending colon cancer at our institution between 2013 and 2018 were retrospectively evaluated (n = 206). Retroperitoneal surgical resection margin on computed tomography colonography was defined on the basis of the relationship between the advanced tumor area and the retroperitoneum. The relationship between retroperitoneal surgical resection margin on computed tomography colonography and relapse-free survival was analyzed by dividing the patients into positive and negative retroperitoneal surgical resection margin on computed tomography colonography groups.

Results: Two doctors independently evaluated the images. The interobserver agreement rate was 93.7% with a kappa coefficient of 0.78 (95% confidence interval, 0.66-0.90). Retroperitoneal surgical resection margin on computed tomography colonography positivity was observed in 32 of the 206 patients (15.5%). Univariate analysis showed that a positive retroperitoneal surgical resection margin on computed tomography colonography was a poor prognostic factor for relapse-free survival (hazard ratio, 7.07; 95% confidence interval, 2.77-18.0, P < .001). Multivariate analysis with carcinoembryonic antigen, clinical T and N stage as covariates (all P < .10 in univariate analysis) identified only retroperitoneal surgical resection margin on computed tomography colonography positive as a significant independent poor prognostic factor for relapse-free survival (hazard ratio, 3.99; 95% confidence interval, 1.30-12.3, P = .02).

Conclusion: In conclusion, this study revealed that retroperitoneal surgical resection margin on computed tomography colonography positivity is a poor prognostic factor. In cases in which retroperitoneal surgical resection margin on computed tomography colonography is positive, it is recommended not only to secure a wider margin, such as by resecting the Gerota fascia, but also to consider retroperitoneal surgical resection margin on computed tomography colonography positivity as a potential indication for preoperative chemotherapy.