Efficacy of chemotherapy followed by chemoradiation versus initial chemoradiation as part of the total neoadjuvant therapy for patients with locally advanced rectal cancer: An NCDB analysis.

Abstract

e15629 Background: Results from multiple trials lead to modern management for locally advanced rectal cancer, with total neoadjuvant therapy (TNT) followed by surgery. However, the best sequence of different treatment modalities is unclear. Methods: We used the National Cancer Database (NCDB) to identify patients with locally advanced rectal adenocarcinoma. We divided patients into different categories based on the timing of chemo and radiation therapy relative to surgery. We used chi-square and Wilcoxon rank test for unadjusted comparison. To compare treatment efficacy with initial chemotherapy to concurrent chemoradiation in downstaging (clinical to pathological stage), we used a linear mixed effect model (LME) with adjustments on age, sex, race, facility type, and year of diagnosis. Also, we evaluated the probability of having positive lymph nodes in the pathological specimen (N+) in the multivariable logistic regression model with adjustment on the clinical stage in addition to the previously mentioned variables. All analyses were done using R 4.6.2. Results: A total of 100509 patients were identified. Only 695 patients received six cycles of neoadjuvant chemotherapy before concurrent chemoradiation (TNT chemotherapy), and 8677 patients received upfront radiation therapy with neoadjuvant chemotherapy administered within 12 weeks of neoadjuvant radiation therapy (TNT radiation). Patients whose start date of chemotherapy or radiation after surgery were excluded. The median age of participants was 63 (IQR = 54-63), and 83% were white. Patients who had TNT chemotherapy were younger (56.4 VS 59.5, P-value < 0.01), had clinically and pathologically advanced stage (IIIB, IIIC) compared to TNT radiation (64%VS 37% and 33%VS 29%, P-value < 0.01). Patients who received TNT radiation had an upgrade in their pathological stage compared to their clinical stage by 0.67 points in the LME (P value < 0.01). In multivariable logistic regression. TNT chemotherapy had a 17% lower risk of (N+) with an OR of 0.83 (0.95 CI 0.59-1.16). However, it was not statistically significant. The two groups had no difference in OS, with a median OS of 137 months (0.95 CI 110 -NR) and 143 (0.95 CI 137-151), respectively. Conclusions: Upfront chemotherapy before starting chemoradiation could be associated with more significant downstaging. Future trials to validate our finding is warranted. [Table: see text] [Table: see text]