Clinical outcomes of neoadjuvant dual HER2 blockade with pertuzumab/Sigrima and trastuzumab/Vivitra biosimilars: real-world evidence in HER2-positive breast cancer in India

Background: HER2-positive breast cancer is an aggressive subtype with a high risk of recurrence. Neoadjuvant chemotherapy (NACT) combined with dual HER2 blockade improves pathological complete response (pCR) rates in clinical trials; however, real-world evidence on biosimilars Sigrima™ and Vivitra™ in India remains limited. Methods: This retrospective study analysed 571 HER2-positive breast cancer patients enrolled in the ANAYA Care programme. All patients received dual HER2 blockade with Sigrima™ (petuzumab biosimilar) and Vivitra™ (trastuzumab biosimilar), with 495 undergoing NACT. Data on demographics, disease stage, treatment setting, financial assistance, pCR outcomes, and adverse events were collected. pCR was evaluable in 242 patients. Results: Most patients were aged 46-60 years, with stage II disease being most common, followed by stage III and stage I. The majority were treated in private hospitals, with additional representation from government and trust centres. Financial assistance supported chemotherapy access in 194 patients. Among evaluable patients, 182 achieved pCR, yielding a rate of 75.2%. Treatment was well tolerated, with ~90% reporting no adverse events. Observed toxicities were primarily mild to moderate, including nausea, fatigue, stomatitis, cytopenias, and liver enzyme abnormalities; serious events were rare. Conclusions: Dual HER2 blockade with Sigrima™ and Vivitra™ demonstrated high efficacy and favourable tolerability in this real-world Indian cohort. These findings support their use as a practical and effective neoadjuvant treatment option in routine clinical practice.