Background: Tobacco use after a cancer diagnosis can negatively impact treatment outcomes and the National Cancer Institute has funded cancer centers to implement tobacco treatment programs (TTP) as part of cancer care, instead of deferring to primary care. This study aimed to assess whether the TTP at UC Davis (UCD) Comprehensive Cancer Center (CCC) improved tobacco treatment assistance and equity among patients with or without a UCD primary care provider (PCPs). Methods: A repeated cross-sectional sample using Electronic Health Record data was collected every six months from January 2017 to December 2021 (N=83,604). Current smokers aged ≥18 were included in this study (N=4,718). The TTP implementation included provider outreach (starting 2018), referral by medical assistants and staff (2019), care gap outreach (2020), and a streamlined referral order (2021). Assistance was defined as medication or counseling orders. To examine whether the association between PCPs and assistance differs over time, a logistic regression model with an interaction term between PCPs and study year on assistance was estimated using generalized estimating equations (GEE) to account for within-patient correlation. We estimated the odds ratios for receiving assistance among patients with a UCD PCP vs. without a UCD PCP by year using a Bonferroni-Holm adjustment for multiple testing. Results: Characteristics of the patients included 38.2% with UCD PCPs, 38.9% aged 65+ years old, 51.2% females, 66.7% Whites, 47.7% with Medicare, and 28.7% living >50 miles away. The proportion of patients who smoke receiving tobacco treatment assistance significantly increased from 17.0% in 2017 (before the TTP began) to 41.0% in 2021 (P<.001). In 2017, those with a UCD PCP were twice as likely to receive assistance than those without a UCD PCP (22.5% vs. 11.8%; odds ratio [OR]: 2.08; 95% CI: 1.2, 3.5). By 2021, this disparity in receiving assistance between patients with and without a UCD PCP was considerably reduced (44.7% vs. 39.0%; OR: 1.1; 95% CI: 0.8, 1.6). Model 1 adjusted for age, gender, race, distance between patients living from UCD CCC, insurance, department, and doctor visits. Conclusions: Overall, the TTP more than doubled assistance to patients who smoke. The impact was even greater for patients without a UCD PCP by tripling tobacco treatment assistance and achieving equitable proportions similar to patients with a.