e17562 Background: Several prior studies have examined the role of comorbidity on overall survival in ovarian cancer (OC) patients and reported an association between comorbidity and inferior overall survival. However, it is unclear if the inferior survival was solely due to the excess mortality from the comorbidities, or that the comorbidities can impact OC treatment outcomes. Our objective was to determine whether pre-existing Charlson comorbidity index (CCI) was associated with lower likelihood of achieving complete remission. Methods: This retrospective cohort study included patients diagnosed with OC of epithelial subtype between 01/01/2017-06/30/2021 at a large integrated healthcare delivery system in the United States. OC patients were identified from the healthcare system’s cancer registry or via chart review of those with the ICD-10 diagnosis code. Patient’s CCI was determined based on data from the 12-month window prior to OC diagnosis. Patients’ remission outcomes, including complete remission and clinical remission (complete + partial remission) were ascertained via chart review, considering physician’s assessment, CA125 value and imaging evidence. Data on potential confounders (pandemic period, age, race/ethnicity, FIGO stage, prior length of membership, and time to treatment) were obtained from the healthcare system’s electronic medical records. Bivariate and multivariable modified Poisson regressions adjusting for potential confounders were used to evaluate the associations between CCI and achieving complete remission or clinical remission by end of therapy. Results: A total of 799 patients diagnosed with OC were included in our study. Overall, the cohort was racially/ethnically diverse with 46.2% White, 33.8% Hispanic, 12.4% Asian, and 7.6% Black patients. In the crude analysis, those with CCI score=1 and CCI≥2 had lower likelihood of achieving complete remission, compared with those with CCI=0 (no Charlson comorbidity) [RR= 0.84 (0.76-0.93) and RR=0.72 (0.64-0.81), respectively]. In the multivariable analysis, those with CCI=1 and CCI≥2 continued to have lower likelihood of achieving complete remission, compared with those with CCI= 0 [RR= 0.84 (0.77-0.92) and RR=0.81 (0.72-0.91), respectively]. Similar findings were observed for clinical remission, although the associations were attenuated: RR= 0.95 (0.89-1.01) for CCI=1 and RR=0.92 (0.86-1.00) for CCI≥2 vs. CCI=0. Conclusions: Having Charlson comorbidity was associated with lower likelihood of achieving complete remission in OC patients. This finding suggest that pre-existing comorbidities may contribute to inferior survival via, at least in part, adversely affecting the likelihood of achieving complete remission. The potential mechanisms underlying this association should be further studied to inform patient management.