Factors predictive of receiving neoadjuvant versus adjuvant chemoradiotherapy in locally advanced rectal cancer and the impact on overall survival.

Abstract

686 Background: Neoadjuvant chemoradiotherapy (NCRT) is generally accepted as the optimal treatment strategy compared to adjuvant chemoradiotherapy (ACRT) for locally advanced rectal cancer due to improvement in local control and reduced toxicity. However, NCRT has not been shown to improve overall survival (OS). We investigated the effect of NCRT versus ACRT on OS as well as the impact of demographic factors and clinical stage for the selection of each treatment approach utilizing the National Cancer Data Base. Methods: Adult patients with stage II and stage III adenocarcinoma of the rectum diagnosed from 2004-2013 were included. Chi-square analysis was used to compare demographic variables and clinical stage between the NCRT and ACRT treatment groups. Univariate and multivariate logistic regression modeling was used to identify factors predictive of each treatment strategy. Kaplan Meier and log-rank analysis along with propensity score matching was performed to determine the effect on OS. Results: A total of 20,262 patients were identified: 17,737 (87.5%) received NCRT and 2,525 (12.5%) received ACRT. Utilization of NCRT increased over the study period (p < 0.01). Factors associated with receipt of NCRT on multivariate analysis include: treatment at an academic institution (OR 0.76, 95% CI 0.68-0.85), income greater than $46,000 (OR 0.79, 95% CI 0.67-0.92), and living greater than 50 miles from a treatment facility. Factors associated with receipt of ACRT on multivariate analysis include: female sex (OR 1.12, 95% CI 1.01-1.24), Charlson comorbidity index of 1 (OR 1.18, 95% CI 1.04-1.34), and radiotherapy dose greater than 5040 centigray (OR 1.76, 95% CI 1.56-1.98). Compared to ACRT, NCRT was associated with a decreased risk of death on multivariate analysis (HR 0.91, 95% CI 0.84-1.00), which persisted after propensity score analysis. Conclusions: The use of NCRT for locally advanced rectal cancer is increasing and is associated with an OS benefit compared to ACRT.