340 Background: About 20% of Americans speak a language other than English at home, among these over one-third experience language barriers when interacting in English. These populations face additional barriers, which can lead to adverse outcomes in the case of a cancer diagnosis. Diverse older adults are at highest risk for sub-optimal care and toxicity from cancer therapies due to the intensity of treatment, their age, comorbidities, in addition to the burden of historic inequities they experience due to sub-optimal communication and insufficient communication of risk. Methods: This retrospective observational study explores the role of language barriers on patient characteristics among patients diagnosed with advanced left-side breast cancer (LSBC). LSBC requires radiotherapy which can pose a risk for cardiotoxicity. Electronic medical records for N=1795 patients were extracted at a tertiary cancer center; analyses were conducted on a secure virtual research desktop using SAS 9.4. This study was IRB approved. Results: Overall, most patients were female (99.5%) and NH White, with a large proportion of Latine patients 17.8%. Most were married or had a partner (49.6%) and were on Medicare (43.2%) or private insurance (34.7%), very few were on Medicaid (5.0%). 9.7% reported a disability that left them unable to work and 13.3% of patients requested an interpreter at their last encounter. Nearly 9% of patients reported a history of heart disease. When we compared patients by those that did and did not request an interpreter as a proxy for limited English proficiency (LEP), we found that patients who were reported Spanish as their preferred language (84.8%, p<.0001) were more likely to be request an interpreter. This group was followed closely by speakers from languages spoken in the Middle East and N. Africa (MENA) region (80.5%, p<.0001). Conversely, we observed patients on Medicaid to be more likely to request an interpreter vs other payer types (39.3%, p<.0001), finally we found significantly fewer patients with a history of heart disease experiencing language barriers. Conclusions: Our assessment demonstrates language barriers remain a significant barrier for Spanish and MENA-region breast cancer patients. Patients with language barriers may have different risk factors and unique needs that require further study. Thus, improved outcomes can be encouraged with tailored management and support for communication barriers.