eP184 - National Trends of Using Immunotherapy for Rectal Cancer. an Analysis of National Cancer Database

Purpose/Background: Immunotherapy for rectal cancer, according to the new NCCN guidelines, is recommended for mismatch repair-deficient (dMMR) or high microsatellite instability (MSI-H) non-metastatic, locally advanced, or for locally unresectable or medically inoperable rectal cancer.A recent study by Cercek et al. revealed that dMMR locally advanced rectal cancer was highly sensitive to neoadjuvant single-agent PD-1 blockade, with all 12 patients experiencing a complete response to therapy. The latest update of this study claims that all 50 patients had a complete response and did not require radiation or surgery.Several recent studies suggest that immunotherapy is poised to transform rectal cancer treatment due to its effectiveness, low toxicity, potential for rectal preservation, and ability to mitigate the side effects of pelvic radiotherapy.Methods/Interventions: The objective of this study was to explore the trends of immunotherapy use in patients with rectal cancer and to determine factors associated with increased use. This retrospective cohort study was conducted using the National Cancer Database (NCDB). We evaluated all patients with rectal adenocarcinoma who were diagnosed from 2004 to 2020. Given that the NCDB does not record the dMMR/MSI-H status of rectal cancer patients, we looked at aggressive histology (poorly differentiated, colloid, signet ring cell, and mucinous cancers) to estimate if it can be used as a substitution for the number of dMMR/MSI-H patientsResults/Outcomes: A total of 332,869 patients with rectal adenocarcinoma were identified in the NCDB from 2004 to 2020. Of these, 10,434 patients received immunotherapy. The use of immunotherapy increased from 0.2-0.7% in 2013 to 3.4%, and further to 7.8% in 2020. Locally advanced rectal cancer patients (T3-T4 N any or T1-2 N1-2) constituted less than 10% of the entire group of rectal cancer patients receiving immunotherapy. Additionally, we assessed how many of these patients had unfavorable histology. Demographic, patient, hospital, and tumor characteristics were evaluated to determine factors associated with increased use of immunotherapy. Furthermore, we determined the overall survival of rectal cancer patients who received immunotherapy.Conclusion/

Discussion: The use of immunotherapy in patients with rectal cancer has significantly increased on a national level from 0.7% to 7.8%, with the most prominent growth occurring since 2013. This data will serve as a baseline for future studies.Trends of using Immunotherapy for rectal cancer from 2004 to 2020