Abstract Background: Approximately 30% to 50% of breast cancer patients experienced mental distress prior to the advent of COVID.The delayed access to cancer treatment due to the outbreak of COVID -19 pandemic posed a unique challenge to breast cancer patients and caused a significant level of mental distress among them. In the current research, we examined the psychological impacts of COVID on breast cancer patients in China using Symptom Checklist-90-R (SCL-90-R). Method: Participants were breast cancer patients at the outpatient clinic of Xijing hospital. The study was conducted virtually, and the questionnaires were distributed via Wenjuanxing, the Chinese alternative of Qualtrics. The researchers were healthcare workers affiliated with Xijing hospital, and the survey was sent to a breast cancer patient support group which included 1399 cancer patients and 6 healthcare workers. The initial sample consisted of 199 participants who signed an informed consent form to participate in the study. The inclusion criteria were as follows: 1) diagnosed with breast cancer, 2) aged 18 years or above, and 3) had no history of cognitive impairment or previous diagnosis of psychiatric disorders. The validated Mandarin version of the SCL-90-R (Wang, 1984) was then given to the participants to evaluate their psychological status.Categorical variables were summarized as numbers and percentages; continuous variables were described as mean (M) ± standard deviation (SD). Data were analyzed using IBM SPSS Statistics Version 26. Results: Participants (N = 195) filled out the SCL-90 questionnaire in February, 2020. All participants were female breast cancer patients treated at Xijing hospital, among which 16.41%, 36.41%, 19.49%, and 28.21% had respectively received treatment for less than a year, 1-3 years, 3-5 years, and 5 years or more. 64.62% of the patients were at stage I; 0.77% were at stage II and III; 4.62% were at stage IV according to TNM classification. The molecular type of participants is as follows: 47.2% of ER+ HER2-, 31.8% of HER2+, and 21.0% of Triple negative.Participants whose treatments continued to be delayed, on average, reported an elevated general psychopathology score (M = 1.48, SD = 0.47) compared to participants whose treatments were resumed (M = 1.30, SD = 0.34), and the difference was statistically significant, t(193) = 2.96, p = .003, d = 0.44, 95%Cl [0.06, 0.30]. The one-way ANOVA revealed a marginally significant effect of length of treatment delay on general psychopathology score, F(4, 190) = 2.09, p = .08, η^2 = .04. Follow-up multiple comparison analysis showed that participants who had their treatment delayed for 3 weeks to 1 month (M = 1.70, SD = 0.70) reported significantly higher general psychopathology scores than participants whose delay in treatment was less than 1 week (M = 1.34, SD = 0.40), p = .05. General health status (p < .001) and current treatment status (p = .02) are the only two variables that were statistically associated with general psychopathology score.Poorer perceived health status and current delay in treatment were associated with higher general psychopathology score, Additionally, younger age was associated with higher interpersonal sensitivity (p = .01) and hostility (p = .006). Conclusions: We found that breast cancer patients at an advanced stage were more likely to experience psychological symptoms with longer treatment delay, and whose treatments continued to be delayed reported elevated psychological symptoms than individuals whose treatment were resumed, regardless of treatment type. Additionally, a treatment delay of more than three weeks might have exacerbated breast cancer patients’ psychological symptoms, whereas a short-term delay of less than three weeks was less likely to have a significant effect on one’s mental well-being. Table 1. Demographic Characteristics and Health Status of The Participants. Table 2A: Multiple Regression analysis for SCL-90 dimensions. Table 2B: Multiple Regression analysis for SCL-90 dimensions. Citation Format: Yijia Wang, Yuqing Yang, Changjiao Yan, Jixin Yang, Hongliang Wei, Wen Ma, Nanlin Li. The Psychological Impacts of COVID-19 on Breast Cancer Patients in China [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P6-05-13.