Trends in brachytherapy use and survival outcomes in rectal adenocarcinoma: Insights from the National Cancer Database.

168 Background: In the U.S. alone, approximately 45000 people are diagnosed yearly with rectal adenocarcinoma. Surgical resection is the most common treatment for rectal cancers, with neoadjuvant chemoradiation therapy typically utilized. The most frequent method of neoadjuvant radiation has been external beam radiation therapy, but brachytherapy (BT) options, like high-dose rate BT, are of recent interest due to studies showing their benefit in clinical response to treatment, specifically for those who are older or have comorbidities. The goal of this study was to identify trends in the utilization of BT for treating rectal adenocarcinoma, as well as the prognosis of patients who receive BT compared to those who do not, with age stratification. Methods: Patients diagnosed 2004 - 2022 within the National Cancer Database (NCDB) with the histology code 8140 of rectal adenocarcinoma were identified. The trend of BT utilization yearly rate was determined by calculating the number of patients receiving BT/number of patients receiving radiation. Kaplan-Meier curves and log-rank analysis were calculated for patients who received any type of BT versus those who received other forms of radiation. Similar graphs were calculated stratified by age ( ≥ 65 years and < 65 years of age). Data was analyzed using R version 4.4.2 with α = 0.05. Results: 435919 patients were identified in this study with rectal adenocarcinoma, with 680 of these patients treated with one of several types of BT in the NCDB. Trend analysis showed an overall increase in utilization in BT as a form of treatment from 2004 (n = 31, 0.16%) to 2011 (n = 55, 0.27%). However, 2011 to 2022 (n = 17, 0.06%) saw an overall decrease in the utilization rate. The Kaplan Meier plot with log-rank analysis showed p < 0.001 in all ages, with survivorship being greater in the group with no BT. When stratified by age < 65, the log-rank calculation revealed a significant difference, with the BT receiving group having a worse survival outcome ( p < 0.001 ). Patients 65+ showed no significant difference in survival ( p = 0.084 ). Conclusions: The findings of this study are two-fold. The findings of undulating trends in BT utilization highlight a need for more robust clinical trials assessing the role of BT in rectal adenocarcinoma. With the unique training requirements and facilities needed to perform BT, some institutions may be wary of investing their resources in building rectal BT treatment programs. Secondly, current rectal BT is recommended in one of two settings: patients with comorbidities or the elderly. With the finding of no significant difference in survivorship in patients 65+ years and recent literature citing increased sphincter function and decreased surrounding tissue damage, the use of BT in rectal adenocarcinoma is supported.