Association of Radial Margin Positivity With Colon Cancer

Importance: In colon cancer, radial margin positivity (RMP) is defined as primary disease involvement at the cut edge of the mesentery or nonserosalized portions of the colon. Although extensively studied for rectal malignancies, RMP has unclear prognostic implications for tumors of the colon.

Objective: To determine the effect of RMP on perioperative outcomes as well as survival and disease-free survival in colon cancer.

Design, Setting, And Participants: A retrospective cohort study including all patients with surgically treated colon cancer at a tertiary care center from January 1, 2004, through December 31, 2011. The cohort was retrospectively extracted from an institutional patient data repository and included in a data repository maintained prospectively starting June 1, 2011, to April 1, 2014. Participants included 984 patients with surgical colon cancer in the given period, excluding patients with intramucosal tumors (n = 47), palliative resections (n = 24), and patients where radial margin status was not assessable (n = 16).

Main Outcomes And Measures: Surgical characteristics, postoperative staging, and long-term outcomes, including recurrence and disease-free survival.

Results: Of the 984 included cases, 52 (5.3%) had an involved radial margin. Patients with RMP had much higher rates of multivisceral resection (40.4% vs 12.8%; relative risk, 3.16 [95% CI, 2.18-4.58]; P < .001) and conversion (50.0% vs 13.7%; relative risk, 3.78 [95% CI, 1.56-9.18]; P = .01). All patients with RMP had American Joint Committee on Cancer stage II cancer or higher, with higher rates of node positivity (86.5% vs 38.8%; relative risk, 2.23 [95% CI, 1.95-2.55]; P < .001), metastasis (34.6% vs 6.7%; relative risk, 5.20 [95% CI, 3.34-8.11]; P < .001), extramural vascular invasion (76.9% vs 28.4%; relative risk, 2.71 [95% CI, 2.26-3.24]; P < .001), and high-grade tumor (45.1% vs 18.2%; relative risk, 3.01 [95% CI, 2.44-3.88]; P < .001). In patients without baseline metastasis, metastatic disease in follow-up was considerably higher in patients with RMP (37.5% vs 12.5%; relative risk, 3.32 [95% CI, 2.79-3.95]; P < .001), especially peritoneal (18.8% vs 2.6%; relative risk, 7.24 [95% CI, 2.40-21.8]; P < .001) and liver (18.8% vs 6%; relative risk, 3.10 [95% CI, 1.08-8.92]; P = .04) metastasis. In multivariable Cox regression, the hazard ratio for survival adjusted for baseline staging, age, comorbidity, smoking, and neoadjuvant chemotherapy was higher (hazard ratio, 3.39; 95% CI, 2.41-4.77; P < .001) compared with metastasis adjusted for baseline staging, smoking, and neoadjuvant chemotherapy (hazard ratio, 2.03; 95% CI, 1.43-2.89; P < .001). The median follow-up duration for patients alive on April 1, 2014, was 51 months (interquartile range, 33-76 months).

Conclusions And Relevance: An involved radial margin leads to high rates of conversion and multivisceral resection. Although occurring infrequently, RMP is an important stage-independent outcome predictor strongly associated with recurrence, risk of death, and shorter survival. Preoperative assessment, especially imaging, could play a key role in the timely identification of potential patients with RMP to take adequate preparatory surgical and therapeutic measures.