Investigating the real-world outcomes of single- versus multi-agent preoperative chemoradiotherapy for locally advanced rectal cancer: NCDB analysis from 2004-2020.

61 Background: Fluorouracil-based chemoradiotherapy is the standard initial treatment for locally advanced rectal cancer, demonstrating improved pathological response and reduced local recurrences compared to radiation alone. Fluorouracil-based chemo-radiation therapy has no impact on distant recurrences. Oxaliplatin was tested in addition to fluorouracil-based chemo-radiotherapy in clinical trials to improve pathological complete response (pCR), distant recurrence-free survival, and overall survival. The trial results are conflicting. In this study, we aim to compare single-agent (SA) versus multi-agent (MA) chemotherapy using real-world data from the National Cancer Database (NCDB). Methods: The NCDB was used to identify 39,667 patients with rectal cancer who received concurrent chemoradiotherapy between 2004 and 2020. We compared patients who received SA chemotherapy with those who received MA concurrent chemotherapy. The primary outcomes of interest were overall survival and pCR. The groups were compared using univariate analysis and Cox proportional hazard models to adjust for potential confounding factors. Results: Of 39,667 patients with rectal cancer, 24,452 received single-agent (SA) chemotherapy and 14,215 received multi-agent (MA) chemotherapy. Patients in the SA group were of advanced age, had a greater number of comorbidities (as calculated by the Charleson-Dayo score), were treated within community facilities, had a higher income status, were covered by government insurance, were situated on the east coast, and had lower educational attainment compared to those in the MA group (p<0.05). SA group had higher T4 and N1 disease, however MA group had more N2 disease. Upon survival analysis, patient in MA group had higher survival (41.2 vs 38.9 months, p=0.005), however pCR was significantly higher in SA group (10.4% vs 6.4%, p<0.001). Conclusions: MA chemoradiotherapy for rectal cancer improves survival, with the SA regimen showing enhanced complete pathological response. Differences in baseline characteristics may explain the outcomes. While MA chemotherapy offers modest overall survival benefits, potential toxicity needs to be considered and confirmed in future studies. Comparison between single agent vs multi-agent chemo-radiotherapy group. Outcome Single-agent chemotherapy Multiagent chemotherapy Chi Squared p-value No readmission within 30 days of surgical discharge 22,727 (89.3 %) 12,921 (90.9 %) <0.001 30-day mortality after surgery 360 (1.5 %) 59 (0.5 %) <0.001 90-day mortality after surgery 716 (3.0 %) 158 (1.3%) <0.001 Median duration of surgical admission 6.0 5.0 <0.001 Median survival-vital = deceased (months) 38.9 41.2 0.005 Median survival-vital = alive (months) 66.9 52.0 <0.001 Pathological complete response (pCR) 2,644 (10.4%) 904 (6.4%) <0.001