Changes in treatment and outcomes of stage II/III rectal cancer patients treated with trimodality therapy (TT) between 2006-2016: An NCDB analysis.

Abstract

32 Background: Trimodality therapy (TT) remains standard for stage 2/3 rectal cancer and emerging evidence supports better outcomes with total neoadjuvant therapy (TNT) than similar therapy given post-operatively (Post-op). Real-world practice patterns and sequence of TT have significant implications on rectal cancer quality of care, outcomes and clinical trial design, and are not well described. Methods: The National Cancer Database was used to identify patients with clinical (c) stage 2/3 rectal adenocarcinoma diagnosed between 2006-2016, while pathologic (p) stage 2/3 was used when c stage was missing. Patients were included if they received Chemo/Radiation (C/RT), single or multiagent (SA or MA) chemotherapy (CT) and surgery. TNT was defined as receipt of pre-op C/RT and MA CT and no post-op therapy. Survival analyses were performed using Kaplan-Meier (KM) estimates and Cox univariate and multivariate hazard ratios (HRs) adjusted for TNT group, sex, race, year of diagnosis, stage, facility type, and age of diagnosis. Five-year KM survival proportions were limited to years 2006-2012, while Cox HRs were estimated from 2006 to 2015. Results: Of 32,467 patients who received TT, 8883 (27%) received TNT and 23,584 were classified no-TNT. TNT and no-TNT cohorts were numerically similar in age, race and gender. A significantly higher proportion of pStages 0-2 patients were observed in the TNT vs the no-TNT cohorts (61% vs. 48%, p < .001). In analysis of annual treatment patterns of the whole cohort, a gradual reduction in Post-op C/RT was observed between 2006 (28%) and 2016 (8%, p < .001), while use of TNT and MA CT did not increase. A migration to lower pStages 0/1/2/3 was seen between 2006 (1/10/31/57%, respectively) and 2016 (3/22/29/45%) (2016) (p < .001). Five-year OS analysis showed superior OS for Pre-op vs Post-op C/RT (74 vs 69%, HR = .81, p < .001), and MA CT vs. SA CT (76 vs 71%, HR = 0.79, p < .001) but inferior 5-y OS for the TNT vs. no-TNT cohorts (74 vs 78%, HR = 1.17, p < .001). Conclusions: Between 2006-16, a minority of patients treated with TT for stage 2/3 rectal cancer received TNT which did not increase over time. Significant annual shifts from Post-op C/RT to Pre-op C/RT, and migration to lower pStages were seen during this time period. Pre-op C/RT and MA CT were associated with improved OS, while TNT patients experienced inferior OS vs. the no-TNT cohort, possibly related to confounding factors in this observational cohort; multivariate sub-group analysis to be presented. Emerging evidence in support of TNT may further change treatment patterns and outcomes. [Table: see text]