A retrospective study of pyrotinib for advanced salivary duct carcinoma (SDC) with positive HER2 expression.

Abstract

e18148 Background: Salivary duct carcinoma (SDC) is a rare subtype of thyroid cancer with a poor prognosis. The efficacy and safety of human epidermal growth factor receptor 2 (HER2)-targeted therapy for SDC have been reported in prospective studies. Here, we report the efficacy of a novel HER2-targeted agent, pyrotinib, a small molecule, irreversible, pan-HER receptor tyrosine kinase inhibitor that targets the epidermal growth factor receptor and HER2, as well as HER4, in the treatment of advanced HER2-positive SDC. Methods: Patients with advanced HER2-expressing salivary duct carcinoma treated with pyrotinib after standard treatment or without any available standard treatment were included in this analysis. HER2 expression was defined by IHC and/or amplification by ISH or NGS via local testing. RECIST version 1.1 was used for efficacy assessments by investigators. Results: A total of 11 patients were enrolled in the study from 7 March 2019 to 31 December 2024. The median age of the patients was 64.2 years (range 35-85 years). The majority of patients were male (81.8%). As for HER2 status, eight patients were IHC3+ and three patients were IHC2+. Pyrotinib was administered as first-line therapy for three patients and as second-line or above for eight patients. Six patients received pyrotinib as monotherapy. All patients were evaluated for efficacy, with the best overall responses being PR in six patients and SD in four patients, resulting in an ORR of 54.5% (95% CI, 23.4%-83.3%) and DCR of 90.9% (95% CI, 58.7%-99.8%).The median progression-free survival was 8.53 months (95% CI, 5.77-NA), and the median overall survival had not yet been reached. It is noteworthy that five patients continued to utilise pyrotinib after disease progression, achieving prolonged disease control when administered in conjunction with local therapy or other systemic therapies. The most common adverse reactions were grade 1-2, with one patient discontinuing due to stool intolerance and the remaining patients having no grade 4 adverse reactions. Conclusions: Pyrotinib showed promising antitumor activity for advanced HER2-expressing SDC with favorable survival benefits and manageable toxicity.