Datopotamab deruxtecan versus chemotherapy in previously treated inoperable/metastatic hormone receptor-positive HER2-negative breast cancer: safety and patient-reported outcomes from the phase III TROPION-Breast01 study

BACKGROUND: In TROPION-Breast01 (NCT05104866), datopotamab deruxtecan (Dato-DXd) improved progression-free survival by blinded independent central review versus investigator's choice of chemotherapy (ICC) in patients with inoperable/metastatic hormone receptor-positive, human epidermal growth factor receptor 2-negative (HR+/HER2-) breast cancer, who had disease progression on endocrine therapy and for whom endocrine therapy was unsuitable, and who had received 1-2 prior lines of chemotherapy in the inoperable/metastatic setting. We report detailed safety data and patient-reported outcomes (PROs) from the final analysis. METHODS: Patients received Dato-DXd (6 mg/kg every 3 weeks) or ICC (eribulin/capecitabine/vinorelbine/gemcitabine). Mouthwash was advised (steroid mouthwash strongly recommended for Dato-DXd), and ophthalmologic assessments were carried out per protocol. Safety and time to deterioration (TTD) in global health status/quality of life (GHS/QoL), pain, and physical functioning, using the European Organisation for Research and Treatment of Cancer QoL Questionnaire-Core 30, were secondary endpoints; exploratory PROs were also assessed. RESULTS: With Dato-DXd (n = 360), nausea was the most common treatment-related adverse event (AE; 51.9%, grade ≥3: 1.4%). The AEs of special interest (grouped terms), treatment-related oral mucositis/stomatitis and ocular surface events, occurred in 57.2% (grade ≥3: 7.2%) and 43.9% (grade ≥3: 1.9%) of patients, respectively. Per protocol recommendations, most patients receiving Dato-DXd received anti-emetics (76.7%), prophylactic mouthwash (77.2%), or artificial tears (71.7%). Adjudicated drug-related interstitial lung disease/pneumonitis with Dato-DXd was mostly low-grade (3.9%; grade ≥3: 0.8%; one grade 5 event). Hematologic toxicity was the most notable feature of the ICC safety profile (n = 351). TTD in GHS/QoL, pain, and physical functioning was delayed with Dato-DXd versus ICC. Patient-reported symptomatic AEs were generally consistent with the clinician-reported AE profile in both arms. CONCLUSION: Safety and PRO data from TROPION-Breast01 complement the improvements in efficacy demonstrated with Dato-DXd versus ICC, supporting Dato-DXd as a treatment option for patients with previously treated, inoperable/metastatic HR+/HER2- breast cancer.