Abstract 911P
Background
SDC is an aggressive subtype of salivary gland cancer. In R/M disease, androgen deprivation therapy (ADT) resulted in response rates (RR) of 18-53% in androgen receptor-positive SDC. SDCs are HER2-positive in 29-46% of cases and have shown RR of 70% on docetaxel and trastuzumab. Here, we present the results of HER2-positive SDC patients treated with DTP and subsequent T-DM1.
Methods
Retrospective case series from a tertiary hospital. HER2 status was assessed by immunohistochemistry and in situ hybridization. DTP consisted of docetaxel (IV 75 mg/m2), trastuzumab (IV 8 mg/kg, followed by 6 mg/kg or SC 600mg), and pertuzumab (IV 840 mg, followed by 420 mg) given 3-weekly. After 6 cycles, only trastuzumab and pertuzumab were continued until disease progression or intolerable toxicity. After disease progression on DTP, T-DM1 (IV 3.6 mg/kg, 3-weekly) was considered for patients with clinical benefit on the first-line of anti-HER-2 therapy and a WHO PS 0-1. The overall RR (ORR) was scored by RECIST v1.1. Progression-free survival (PFS), overall survival (OS) and toxicity are presented.
Results
From 2015-2020, 13 HER2-positive SDC patients received DTP. Median age was 61 years (range: 48-75), 77% were male. Prior systemic therapy included adjuvant ADT (23%), palliative ADT (46%) and chemotherapy (8%). Twelve patients were RECIST evaluable, ORR was 58%: 1 complete response (CR) and 6 partial responses (PR). Median PFS was 6.8 months (range: 1.8-26.8+). Seven patients received second-line T-DM1. T-DM1 resulted in ORR of 57% (4 PR) and median PFS was 4.4 months (range: 1.2-17.3). After median follow-up from start of DTP of 15.4 months (range: 5.5-55.0) median OS was not reached. 5/13 patients (39%) developed grade ≥3 toxicity on DTP, including infections (n=3), neutropenia (n=1) and heart failure (n=1). 1/7 patient (14%) developed grade ≥3 toxicity on T-DM1, hyponatremia (n=1).
Conclusions
In R/M HER2-positive SDC patients DTP followed by T-DM1 upon progression are promising treatment strategies, leading to responses in the majority of the patients at an acceptable toxicity profile. The median OS was not reached after a median follow-up of 15.4 months.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
C.M.L. Van Herpen.
Funding
Has not received any funding.
Disclosure
C.M.L. Van Herpen: Other, Institutional, Advisory Board, Consultant fees for participation in advisory boards: Bayer; Other, Institutional, Advisory Board, Consultant fees for participation in advisory boards: Bristol-Myers Squibb; Other, Institutional, Advisory Board, Consultant fees for participation in advisory boards: Ipsen; Other, Institutional, Advisory Board, Consultant fees for participation in advisory boards: MSD; Other, Institutional, Advisory Board, Consultant fees for participation in advisory boards: Regeneron; Other, Research Grant: AstraZeneca; Other, Research Grant: Bristol-Myers Squibb; Other, Research Grant: MSD; Other, Research Grant: Merck; Other, Research Grant: Ipsen; Other, Research Grant: Novartis; Other, Research Grant: Sanofi. All other authors have declared no conflicts of interest.