Predictors of survival in rectal squamous cell carcinoma: An analysis from the National Cancer Database (NCDB).

Abstract

672 Background: Rectal squamous cell carcinoma (RSCC) is a rare form of gastrointestinal malignancy. Using the NCDB, we determined the prognostic factors and survival outcomes of RSCC in the United States. Methods: We identified histologically confirmed cases of RSCC from the National Cancer Data Base (2004-2015). Univariate and multivariable methods were used to assess factors associated with survival. Kaplan-Meier method and log-rank test were used to perform overall survival (OS) analysis. Results: Of the 5,527 cases included in our analysis, 67% were female. Median age at diagnosis was 61 years and did not differ by sex. The proportion of patients with stage 1, 2, 3 and 4 diseases were 22%, 16%, 20%, and 11%, respectively (30% unknown stage). Among the ones who received surgical resection of primary tumor, 41%, 30%, 20% and 8% are of stages 1, 2, 3 and 4 respectively. The rate of R0 resection was 54%, 63%, 55% and 38% in stage 1, 2, 3 and 4, respectively. The R0 resection rate was much higher in patients who received neoadjuvant chemo or radiation therapy or both (87%, 78%, 74%, and 57% in stages I, 2, 3 and 4, respectively) as compared to that of their counterparts. On stage wise sub-group OS analysis, stage 1-3 patients had OS benefit from surgery (as compared to no-surgery) (145 vs 90 months, p<0.001) as opposed to 4 disease (16 vs 11 months, p=0.06). Adjuvant radiation therapy improved the median OS in stage 1-3 patients (as compared to no-adjuvant radiation) in patients with positive surgical margins (not reached vs 40 months, p<0.0001). Patients with stage 4 disease treated with radiation therapy had a better median OS than those without (16 vs 6 months, p<0.0001). On therapy wise sub-group analysis, the patients who received surgery only had a median OS of 145 months; surgery + chemoradiation (adjuvant and neoadjuvant) = not reached; whereas patients with chemoradiation only had median OS of 80 months. Conclusions: This is the largest registry-based study on RSCC to date. RSCC had a diverse OS varied significantly according to stage of the disease at presentation and therapy received. Surgical resection of primary tumor was associated with improved OS as compared to that of patients who received chemoradiation.