Abstract PS1-08-01: Safety of Combining Radiotherapy With Sacituzumab Govitecan in Patients With Advanced Triple-Negative Breast Cancer: An International Multicenter Cohort Study

Abstract Background. Antibody-drug conjugates (ADC) such as sacituzumab govitecan (SG) have significantly improved outcomes in advanced triple-negative breast cancer (TNBC). However, many patients undergoing SG require radiotherapy (RT) for symptom control or oligoprogression. Clinical data on the safety of concurrent or sequential SG and RT are scarce. We aimed to evaluate the tolerability and survival outcomes associated with combining RT and SG in real-world clinical practice. Methods. We retrospectively analyzed 303 female patients treated for metastatic or unresectable locally advanced TNBC between August 2021 and May 2025 across multiple oncology centers in Poland, The Czech Republic, and Slovakia. All patients received SG; 66 (21.8%) received RT either prior to (n=33) or during (n=33) SG therapy. Progression-free survival (PFS) was defined as the time from SG initiation to disease progression or death. Overall survival (OS) was defined as the time from SG initiation to death from any cause or last follow-up. Survival was estimated using the Kaplan-Meier method; group comparisons were performed using Fisher’s exact test. Analyses were performed with Stata Statistical Software 19.0 (StataCorp LLC, College Station, TX, USA). Results. Among the 303 patients, the median PFS was 5.1 months in those who did not receive RT (237 patients, 78.2%) and 4.2 months in those who did (66 patients, 21.8%; p=0.42). The 6-month PFS rates were 42.0% (95% CI, 35.3-48.5%) and 36.9% (95% CI, 24.5-49.3%), respectively. Median OS was 11.9 months in the non-RT group versus 9.3 months in the RT group (p=0.14), with 12-month OS rates of 49.5% (95% CI, 42.1-56.4%) and 36.2% (95% CI, 23.7-48.8%), respectively. Patients in the RT group more frequently had central nervous system metastases (27.3% vs 4.6%, p