EP277 - Do Tumor Deposits [N1c] Have the Same Risk Pattern as High-Risk Features in Colorectal Cancer?

Purpose/Background: Colorectal cancer remains a major cause of morbidity and mortality worldwide. Precise risk stratification guides treatment and improves outcomes. The N1c classification, denoting the presence of tumor deposits without nodal involvement has emerged as a distinct prognostic factor. However, its implications for recurrence risk compared to other high-risk tumor features is not fully established.

Methods/Interventions: We conducted a retrospective cohort study comparing patients with N1c disease to high-risk tumors (obstructing, perforated, or T4). N1c disease was defined as the presence of tumor deposits without positive lymph nodes. Adult patients from 2010-2018 who underwent curative surgery for non-metastatic, stage III, colorectal adenocarcinoma were included. Data, including demographic, perioperative, and pathology, were obtained from a prospectively maintained database and chart review. Analyses included descriptive, comparative, and survival assessments.

Results/Outcomes: A total of 98 patients were included: 71 with high-risk tumors and 27 with N1c disease. The groups were comparable in demographics: age (65.1 vs. 66.9 years; p=0.57), gender (56.3% vs. 55.6% male; p=0.94), race (p=0.63), BMI (27.7 vs. 28.3 kg/m²; p=0.68), and tumor location (p=0.07). There was a trend towards higher ASA scores in the N1c group (p=0.06), indicating slightly more comorbidities. Neoadjuvant therapy was more common in the N1c group (37%) compared to the high-risk group (12.7%; p=0.005).

Operative time was significantly longer for N1c cases (247.1 vs. 192.4 minutes; p=0.04). No significant differences were found in length of hospital stay (p=0.15), rates of ostomy creation (p=0.29), intraoperative complications (p=0.73), or postoperative complications (p=0.51). Tumor characteristics showed notable differences: the high-risk group had a higher proportion of obstructing tumors (26.8% vs. 3.7%; p=0.01) and perforated tumors (15.5% vs. 0%; p=0.03). Surgical procedures differed, with high-risk patients undergoing more extensive resections such as en bloc resection and total abdominal colectomy. Tumor deposits were present in all N1c cases (100%) versus only 32.4% in the high-risk group (p < 0.001). Tumor size was similar (4.3 vs. 5.1 cm; p=0.11), but there was a trend toward more lymph nodes collected in high-risk patients (36.3 vs. 28.1; p=0.20).

Pathological features such as grade, perineural/lymphovascular invasion, and mucinous histology showed no significant differences. The recurrence rate was comparable between groups: 39.4% in high-risk and 33.3% in N1c patients (p=0.57). The time to recurrence was similar (13.0 vs. 12.5 months; p=0.87). Kaplan-Meier analysis revealed no significant differences in recurrence-free survival over 12 months (p=0.86) or overall survival over 60 months (p=0.76). Both survival curves demonstrated gradual declines without divergence, indicating that N1c status did not significantly impact long-term outcomes in this cohort.

Conclusion/Discussion: Despite differing operative and pathological features, N1c disease was not associated with higher recurrence or poorer survival compared to high-risk tumors. Larger, longer-term studies are needed to clarify its role in risk stratification and management of colorectal cancer.

Figure 1. Kaplan-Meier Curve for Recurrence-Free Survival with N1c Disease versus High-Risk Tumors
Table 1. Perioperative and tumor-specific variables.
Data are presented as mean ± SD or frequency (percentage).