108P Safety results of post-neoadjuvant T-DM1 in the Italian compassionate use program (GIM26-TRASTHER study)

T-DM1 is standard treatment in patients (pts) with HER2-positive breast cancer residual disease after neoadjuvant therapy. The GIM26-TRASTHER study of the Gruppo Italiano Mammella (GIM) group collects data from Italian compassionate use program that anticipated drug reimbursement. Inclusion criteria mirrored Katherine trial. We registered adverse events (AEs) were considered to be certainly/probably/possibly related as per investigators’ judgement. used descriptive analysis for presentation. 202 pts included 18 centers between Sep 2021 and Dec 2022. Median age was 52 years (IQR 45-59), 30% (n=61) premenopausal 56% (n=113) had at least 1 comorbidity (main: thyroid disorders 13%, hypertension dyslipidemia 4.5%). Smoking status available 156 pts, 39 (25%) current or former smokers. As therapy, 85 % (n=169) received anthracycline plus taxane chemotherapy 25 (n=50) dual anti-HER2 blockade. Overall, 320 T-DM1-related AEs any grade 105 (52%). G3 observed 11 (5.4%), while there no G4-G5 AEs. Most prevalent transaminases increase (19.8%), thrombocytopenia (15.3%), nausea vomiting (13.3%), fatigue (10.9%), myalgia arthralgia (7.4%), peripheral neuropathy (6.4%) neutropenia (5%). For 42 out (20.8%), reduced dose, delayed discontinued due toxicity. Pts experiencing older (54 vs 51, p=0.046), more frequently smokers (34% 16.6%, p=0.034), less exposed anthracyclines (79% 92%, p=0.012) compared those No impact menopausal status, pre-existing comorbidities type therapy observed. In this multicentric study, new safety concerns adjuvant Toxicity seems mostly linked by patient’s characteristics, underlying importance evaluating profile anticancer drugs a real-world setting selected pts. Further analyses, including survival outcomes, are ongoing.