Recurrence Rate of High-Risk Stage II Sigmoid Colon Carcinoma Without Adjuvant Chemotherapy
High-risk stage II colon cancer patients who do not receive adjuvant chemotherapy have a 3-year recurrence rate of approximately 27% (73% recurrence-free survival), based on the most robust genomic validation data from the ColoPrint assay in T3/MSS patients. 1
Evidence-Based Recurrence Rates by Assessment Method
The recurrence rates for high-risk stage II colon cancer without adjuvant chemotherapy vary depending on how "high-risk" is defined:
Genomic Risk Stratification (Most Precise)
- ColoPrint high-risk classification: 3-year recurrence-free survival of 73% (27% recurrence rate) in T3/MSS subset patients without adjuvant therapy 1
- Oncotype DX high recurrence score: 3-year recurrence rate of 22% in the high-risk genomic group 1
- These genomic assays identify risk independent of traditional clinicopathological features 1
Traditional Clinicopathological High-Risk Features
When high-risk is defined by conventional features (T4 tumors, perforation, obstruction, poorly differentiated histology, lymphovascular invasion, <12 lymph nodes examined):
- 5-year disease-free survival: Approximately 80-85% without adjuvant chemotherapy, translating to a 15-20% recurrence rate 1, 2
- Patients with 2-3 poor prognostic features: 5-year tumor-specific survival drops to 88.9% (with 2 features) and 87.5% (with 3 features), indicating recurrence rates of 11-13% 3
Context from Recent Meta-Analysis
A 2015 systematic review of modern cohorts (patients included after 1995) found that stage II colon cancer patients operated without adjuvant chemotherapy had a 5-year disease-free survival of 82.7% (95% CI 80.8-84.6%) in high-quality studies 2. This represents an approximately 17% recurrence rate at 5 years for unselected stage II patients.
Critical Nuances in Risk Assessment
The definition of "high-risk" substantially impacts recurrence rates. The NCCN guidelines acknowledge that the current definition of high-risk stage II disease is inadequate—many classified as high-risk do not recur, while some average-risk patients do 1. The MOSAIC trial analysis revealed that 54% of patients classified as "high-risk" were in that category solely due to inadequate lymph node sampling (<12 nodes), which may not represent true biological high-risk disease 1.
Specific High-Risk Feature Impact
Individual high-risk features confer different recurrence risks:
- T4 tumors: Strongest independent predictor of recurrence 4
- Lymphovascular invasion: 5.2-fold increased risk of recurrence 4, 5
- Obstruction at presentation: Significantly decreased disease-free survival (p=0.008) 5
- Poorly differentiated histology: 5.1-fold relative risk increase 4
- Multiple high-risk features: Patients with ≥2 high-risk features have 5-year disease-free survival of 74.8% (25% recurrence rate) compared to 87.3% (13% recurrence rate) with one risk factor 4
Microsatellite Instability Considerations
MSI-H/dMMR tumors have markedly better prognosis and represent 22% of stage II colon cancers 1. These patients have excellent outcomes without adjuvant chemotherapy and should not be included in high-risk calculations for treatment decisions 1, 6. For MSS/pMMR high-risk stage II patients specifically, the recurrence risk is higher than the overall stage II population 1.
Clinical Implications
The wide range of reported recurrence rates (13-27% depending on definition) underscores why the ASCO and NCCN guidelines emphasize that most stage II patients—even those with some high-risk features—are cured by surgery alone 1, 7. The absolute benefit of adjuvant chemotherapy in this population is small (3-4 percentage points reduction in recurrence risk) 8, which is why observation remains a reasonable option even for many high-risk patients 1.
For sigmoid colon specifically, there is no evidence that tumor location within the colon significantly alters these recurrence rates in stage II disease, as the high-risk features themselves are the primary determinants of outcome 1.