Multiple research studies have demonstrated racial, socioeconomic status (SES), and neighborhood disparities in first-line treatment of colorectal cancer patients, including those with metastatic colorectal cancer. However, disparities in adjunct monoclonal antibody treatment disparities have not been explored. The purpose of this study was to assess racial, SES, and neighborhood disparities in adjunct monoclonal antibody treatment of elderly metastatic colorectal cancer patients. The research was rooted in 3 theories: the fundamental cause theory, the diffusion of innovations theory, and theory of health disparities and medical technology. Data from the SEER-Medicare database and logistic regression were used to assess the relationship between the variables of interest and adjunct monoclonal antibody therapy. In this study, race (p = 0.070), SES (p = 0.881), and neighborhood characteristics (p = 0.309) did not significantly predict who would receive monoclonal antibody therapy. The results demonstrated a potential improvement in historically documented colorectal cancer treatment disparities. Specifically, historical treatment disparities may not be relevant to newer therapies prescribed to patients with severe disease. The difference could be related to improved access to care or a change in treatment paradigm due to the severity of metastatic colorectal cancer. Future studies aimed at understanding the causes of this social change (i.e., reduced treatment disparities) are warranted. Understanding the root cause of the reduced treatment disparities observed in this study could be used to reduce treatment disparities in other cancer populations.