716 Background: 15-20% of patients with locally advanced rectal adenocarcinoma (LARC) achieve a pathologic complete response (pCR) following neoadjuvant chemoradiation (nCRT). The role of adjuvant chemotherapy has been questioned. Methods: Patients with rectal cancer receiving nCRT in the National Cancer Data Base (NCDB) 2006-2013 data set were evaluated. The primary outcome was overall survival (OS). The association between OS and patient characteristics were examined using multivariable Cox regression models. Results: 2,903 patients were identified who achieved a pCR. The median follow up was 43.2 months. 2,102 received nCRT and 789 received nCRT + adjuvant chemotherapy. Factors significantly associated with OS included age (p<0.001), gender (p=0.011), Charlson-Deyo comorbidity score (CDI) (p<0.001), grade (p=0.029), clinical T stage (p=0.030), and CEA negativity (p=0.002), but not nodal status. The 3-year OS rate was 94% in the adjuvant therapy group as compared to 84% in the nCRT alone group (p<0.001). In considering clinical N-stage, the benefit was comparable for both N+ and N- tumors. Adjuvant chemotherapy was more likely to be given for younger patients (age < 60), lower comorbidity score, higher grade, positive CEA status, higher clinical T stage, and higher clinical N stage. When stratifying by these factors, similar benefits in OS were observed in the adjuvant cohort. Conclusions: Following nCRT and achievement of a pCR, the receipt of adjuvant chemotherapy is associated with improved OS. Patients receiving adjuvant therapy were more likely to be younger and have a low CDI, but have more advanced stage disease. Thus, a selection bias may be present. Nonetheless, in the setting of the already excellent outcome associated with pCR, the additional benefit of adjuvant chemotherapy should be weighed against toxicity.
MR prediction of pathologic complete response and early-stage rectal cancer after neoadjuvant chemoradiation in patients with clinical T1/T2 rectal cancer for organ saving strategy
