Disparities in prophylactic tetracycline use among patients with metastatic colorectal cancer undergoing treatment with EGFR inhibitors.

109 Background: Epidermal growth factor receptor (EGFR) inhibitors have been shown to improve survival in metastatic colorectal cancer and are considered a standard of care option for patients with RAS/RAF wild-type disease. However, anti-EGFR agents are associated with an acneiform rash that can lead to decreased quality of life and early discontinuation of treatment. Prophylactic doxycycline has been shown in a randomized clinical trial to decrease any skin toxicity ≥ grade 2 by 50%. In this study we sought to determine the rate of prophylactic tetracycline use in metastatic colorectal cancer patients receiving anti-EGFR therapy in the United States. Methods: The Flatiron Health Electronic Health Record-derived, de-identified database was used to analyze the records of patients who were at least 18 years old, diagnosed with metastatic colorectal cancer, and received treatment with an anti-EGFR agent (cetuximab or panitumumab). Patients were stratified by receipt of prophylactic tetracycline versus not. This was defined by an order for a tetracycline 28 days before to 1 day after initiation of an anti-EGFR agent. Demographic and clinical characteristics were compared via multivariable logistic regression. The change in percentage of patients who received a prophylactic tetracycline over time was assessed and was compared to the rate of anti-emetic prescription which served as a control to ensure drug administration data was accurately captured. Results: The records of 6,713 patients who met inclusion criteria and received an anti-EGFR agent between 2013 and 2023 were included in our analysis. A logistic regression model assessing the association between patient characteristics and the receipt of a prophylactic tetracycline suggested that older age, race (black/African American or Other), presence of RAS mutation, and higher line of therapy were all significantly associated with not receiving prophylactic tetracyclines. Other patient characteristics including gender, ECOG status, mismatch repair status, and RAF mutation status did not appear to impact the likelihood of receiving a prophylactic tetracycline. The rate of prophylactic tetracycline use increased from 10.9% in 2013 to 22.3% in 2023 while the rate of prophylactic anti-emetic remained stable at around 82%. Conclusions: This real-world analysis suggests the use of preemptive treatment for skin toxicity in patients with metastatic colorectal cancer who are treated with an anti-EGFR in US is suboptimal. Disparities in cancer care are also evidenced by lower use of tetracyclines in elderly and African Americans. Randomized controlled trials support the use of prophylactic tetracycline in these patients; thus, further research into the reason for this practice gap is necessary. Educational efforts should be undertaken to improve tetracycline prescribing rates in this population.