Impact of Postoperative Adjuvant Chemotherapy Following Long-course Chemoradiotherapy in Stage II Rectal Cancer.

OBJECTIVES: Use of adjuvant chemotherapy (AC) following neoadjuvant chemoradiation (nCRT) is controversial in rectal cancer (RC). We assessed a multi-institutional database to determine if there was benefit from AC for pathologic stage II RC patients and whether the addition of oxaliplatin to fluoropyrimidine (OXAC) therapy impacted outcomes.

MATERIALS AND METHODS: We included patients who underwent nCRT and had pathologic stage II (ypT3/4 ypN0) tumors. Disease-free survival and overall survival were assessed. Multivariate Cox models adjusting for age, sex, Eastern Cooperative Oncology Group, high-risk features (pT4, poor differentiation, <12 nodes removed, lymphovascular/perineural invasion, or obstruction/perforation), and clinical stage were constructed.

RESULTS: Of 485 patients, 73.6% received AC, of which 25.5% received OXAC. Patients receiving AC were younger (median age 61 vs. 64; P=0.003) and had higher rates of total mesorectal excision (81.5% vs. 78.9%; P=0.049), but had similar high-risk features, performance status, clinical stage, margin status, preoperative carcinoembryonic antigen, and nCRT regimen. In univariate analysis, overall survival was improved with fluoropyrimidine AC compared with no AC or OXAC (P=0.049), but not disease-free survival (P=0.33). In multivariate analysis, any AC, fluoropyrimidine AC, or OXAC did not improve outcomes. After stratifying patients by the presence of high-risk features, elevated carcinoembryonic antigen, margin status, or preoperative clinical stage, we did not identify a group with improved outcomes following AC.

CONCLUSIONS: In this multi-institutional cohort of yp stage II RC patients, we failed to identify a group that derives benefit from AC following nCRT. The addition of oxaliplatin did not appear to improve outcomes when compared with fluoropyrimidine alone.