Salivary duct carcinoma (SDC) is a rare and aggressive subtype of salivary gland cancer, with a median disease-free survival (DFS) of less than 3 years. SDC is androgen receptor-positive (AR+) in 67-96% of cases. In incurable recurrent AR+ SDC androgen deprivation therapy (ADT) has an overall response rate of 18-50%. In this study, high-risk AR+ SDC pts were treated with adjuvant ADT to study the efficacy.
In this retrospective study, surgical resected pts who received adjuvant ADT for stage 4a/b AR+ SDC at the Radboudumc (Nijmegen, the Netherlands) or Istituto Nazionale dei Tumori (Milan, Italy) were collected. As control group, surgical resected pts diagnosed with stage 4a/b SDC between 1990-2014, who did not receive adjuvant ADT were collected by a search of the Dutch pathology database (PALGA). Pts were analyzed for DFS and overall survival (OS) by using Kaplan-Meier survival curves.
18 AR+ SDC pts (median age 64 years [range 32-80]) were treated with adjuvant ADT (Nijmegen n = 11; Milan n = 7) for a median duration of 10 months [range 2-31 months]. All pts had a nuclear AR-staining pattern in > 70% of the cells. They were treated with bicalutamide monotherapy (n = 10), a LHRH analog (n = 1) or a combination of these (n = 7). Treatment was well tolerated. 17/18 pts (94.4%) also received postoperative radiotherapy, of which 4 pts received concurrent chemoradiotherapy (22.2%). The control group consisted of 110 SDC pts (median age 70 years [range 44-100]). 103/110 pts (93.6%) received postoperative radiotherapy, of which 1 pt received concurrent chemoradiotherapy (0.9%). After a median follow-up of 22 months in the ADT-treated SDC pts and 25 months in the control SDC pts, the 3-year DFS was 53.6% and 34.2% (p = 0.137), the 3-year OS was 68.2% and 52.3% (p = 0.198), respectively. The median DFS and OS were not reached in the ADT-treated SDC pts and were 21 months and 46 months in the control SDC pts.
Adjuvant ADT in high-risk AR+ SDC pts did not lead to a significant increase in DFS or OS, but the number of treated pts was limited. Due to the rarity of the disease we could not perform a formal phase II study. Translational research to identify pts which may benefit from ADT is warranted.
Clinical trial identification
Legal entity responsible for the study
Carla M.L. van Herpen
All authors have declared no conflicts of interest.