P-151 the Impact of Adjuvant Chemotherapy Regimens in Stage II Colon Cancer (CC) Patients

The benefit of adjuvant chemotherapy (AdjCT) in all stage II patients (pts) with colon cancer is not clear. Characterization of high-risk subgroups may shed light on this matter. The aim of this study was to determine patterns of AdjCT prescription and its impact on disease-free survival (DFS) in stage II CC. Unicentric retrospective cohort of pts with stage II colon adenocarcinoma identified on the Portuguese national oncologic database between 2007 and 2018. Pts were categorized into two groups: not receiving and receiving AdjCT; AdjCT was characterized as capecitabine monotherapy (Cap) vs oxaliplatin-based (Oxali). We identified 668 pts with stage II CC: 191 were excluded (misclassification, death ≤30 days after surgery, or absence of available pathologic report). A total of 477 pts were treated at our center. 125 pts (26.2%) received AdjCT and we identified six statistically significant factors for this in the univariate analysis: age, higher stage, presence of lymphovascular or perineural invasion, and presence of perforation or obstruction. When controlling for these factors and insufficient lymphadenectomy sampling (ILS) (< .0001) and ILS (OR, 2.879; CI, 1.362-6.084; P = .006) was more likely to receive AdjCT. Considering the AdjCT regimen used, age was the only statistically significant factor: pts >70 yr were more likely to receive Cap than Oxali (OR, 40.625; 95% CI, 9.046-182.440; P < .001). Age kept its significance in the multivariate model when controlling for PS-ECOG, stage and ISL. Oxali was used in 52 pts (49.2%), mostly mFOLFOX. With a median follow-up of 72.2 months, mDFS was not reached (13.9% maturity). Regarding factors that may influence DFS, in the univariate cox regression, there was no difference for gender, PS-ECOG, laterality, perforation, obstruction, or perineural invasion. Age >70 yr (HR, 5.484; 95% CI, 1.885-15.949; P = .002) and lymphovascular invasion (HR, 3.309; 95% CI, 1.215-9.014; P = .019) were associated with worse prognosis. Also, when DFS was analyzed, Cap (vs Oxali: HR, 4.045; 95% CI, 1.116-14.665; P = .033) was associated with poorer outcomes. Considering the impact of the CT regimen on DFS, there was no difference between Cap and Oxali (P = .980) when controlling for age, stage, and lymphovascular invasion. However, age >70 yr (HR, 8.487; 95% CI, 1.383-52.072; P = .021), stage IIB or C vs IIA (HR, 3.346; 95% CI, 1.060-10.560; P = .039), lymphovascular invasion (HR, 3.989; 95% CI, 1.297-12.268; P = .016) kept their significance. In this cohort, younger age, higher stage, lymphovascular invasion or obstruction, and ILS were significantly associated with receiving AdjCT. All factors but age are high risk for CT consideration in major international guidelines. The CT regimen (Cap vs Oxali) had no impact on DFS and the difference found in univariate analysis might be explained by Cap being chosen for pts with poorer biological reserve. Although this study is limited by its retrospective, non-controlled nature, younger age might be a surrogate for fewer comorbidities and better PS, which might explain why older pts were less likely to receive AdjCT, and when administered, Cap was the preferred regimen.