Real-World Outcomes of Subcutaneous PHESGO® in HER2-Positive Breast Cancer: Pathological Response, Sequencing, and Safety

Background: Subcutaneous pertuzumab and trastuzumab with hyaluronidase (PHESGO®) shorten chair time versus intravenous dual HER2 blockade, but real-world Asian data are scarce. Methods: We retrospectively reviewed 47 Asian patients with HER2-positive breast cancer treated with PHESGO® (January 2024–July 2025) across neoadjuvant, adjuvant, and metastatic settings. The primary endpoint was pathological complete response (pCR) in the neoadjuvant cohort; secondary endpoints included sequencing, safety, and metastatic activity. Results: Median age was 65 years. In the neoadjuvant cohort (n = 26), pCR was 65% (17/26). PHESGO®-first regimens achieved higher pCR than anthracycline-first regimens (85.7% vs. 41.7%; p = 0.038). Treatment was generally well tolerated: the most frequent events were dysgeusia (57%), diarrhea (38%), and rash (34%), mostly grade 1–2; one grade ≥3 event (thrombocytopenia) occurred, and no symptomatic cardiac dysfunction was observed. Adverse event profiles were broadly comparable in patients ≥ 70 versus <70 years. In metastatic disease (n = 10), objective response and disease control rates were 56% and 78%, respectively. Conclusions: In routine practice, PHESGO® showed substantial neoadjuvant activity, acceptable toxicity, and workflow advantages. Early use of subcutaneous dual HER2 blockade with taxane may enhance pCR and facilitate delivery; prospective validation is warranted.