Background

The use of chemotherapy among patients with stage II colon cancer is controversial. We aimed to define the utilization and factors associated with the receipt of chemotherapy and the impact of chemotherapy on long-term prognosis among a large, multiinstitutional cohort of patients.

Materials and methods

We identified 876 patients who underwent resection for stage II colon cancer between 2004 and 2013 at one of seven participating institutions. Overall survival (OS) and recurrence-free survival (RFS) time was calculated from the date of the index procedure to the date of death.

Results

A total of 163 patients (18.6%) received adjuvant chemotherapy and this utilization decreased over time (P = 0.003). Younger age (P < 0.001), margin positivity (odds ratio [OR], 12.16; 95% confidence interval [CI]: 2.57-57.52; P = 0.002), and the presence of perineural invasion (OR, 1.24; 95% CI: 1.07-1.44; P = 0.005) increased the likelihood of receiving chemotherapy. Receipt of chemotherapy was associated with improved median OS and RFS. After controlling for all factors, the addition of oxaliplatin to 5-fluorouracil did not affect survival, and there was no difference in OS (hazard ratio [HR], 0.74; 95% CI: 0.27-2.06; P = 0.57) or RFS (HR, 0.71; 95% CI: 0.32-1.58; P = 0.88) with adjuvant treatment, including for patients with high-risk features (OS-HR, 0.63; 95% CI: 0.33-1.19; P = 0.15; RFS-HR, 0.77; 95% CI: 0.32-1.86; P = 0.56).

Conclusions

The utilization of chemotherapy has declined over time after resection for stage II colon cancer. Chemotherapy was not independently associated with improved OS or RFS in this study group, including in patients with high-risk features. Future prospective studies should strive to identify the subset of stage II colon cancer patients that will benefit the most from the addition of adjuvant chemotherapy.

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Background

The role of adjuvant chemotherapy in patients with stage II colon cancer remains to be elucidated and its use varies between patients and institutions. Currently, clinical guidelines suggest discussing adjuvant chemotherapy for patients with high-risk stage II disease in the absence of conclusive randomized controlled trial data. To further investigate this relationship, the objective of the current study was to determine whether an association exists between overall survival (OS) and adjuvant chemotherapy in patients stratified by age and pathological risk features.

Methods

Data from the National Cancer Data Base were analyzed for demographics, tumor characteristics, management, and survival of patients with stage II colon cancer who were diagnosed from 1998 to 2006 with survival information through 2011. Pearson Chi-square tests and binary logistic regression were used to analyze disease and demographic data. Survival analysis was performed with the log-rank test and Cox proportional hazards regression modeling. Propensity score weighting was used to match cohorts.

Results

Among 153,110 patients with stage II colon cancer, predictors of receiving chemotherapy included age <65 years, male sex, nonwhite race, use of a community treatment facility, non-Medicare insurance, and diagnosis before 2004. Improved and clinically relevant OS was associated with the receipt of adjuvant chemotherapy in all patient subgroups regardless of high-risk tumor pathologic features (poor or undifferentiated histology, <12 lymph nodes evaluated, positive resection margins, or T4 histology), age, or chemotherapy regimen, even after adjustment for covariates and propensity score weighting (hazard ratio, 0.76; P<.001). There was no difference in survival noted between single and multiagent adjuvant chemotherapy regimens.

Conclusions

In what to the authors' knowledge is the largest group of patients with stage II colon cancer evaluated to date, improved OS was found to be associated with adjuvant chemotherapy regardless of treatment regimen, patient age, or high-risk pathologic risk features. Cancer 2016;122:3277-3287. © 2016 American Cancer Society.