Biomarker‐Driven Initial Systemic Therapy Enabling Curative‐Intent Treatment in Non‐Metastatic Unresectable Salivary Duct Carcinoma: A Multi‐Institutional Retrospective Study
Satoshi Kano, Daisuke Kawakita, Yoshitaka Honma, Hideaki Takahashi, Toyoyuki Hanazawa, Kiyoaki Tsukahara, Shota Fujii, Kenji Okami, Keisuke Yamazaki, Yushi Ueki, Yuki Saito, Hiroyuki Ozawa, Sae Imaizumi, Tomoyuki Arai, Sho Iwaki, Kenji Hanyu, Mayu Yamauchi, Ryoko Tanaka, Koji Yamamura, Mariko Sekimizu, Chihiro Fushimi, Takashi Matsuki, Yoshitaka Utsumi, Masato Nakaguro, Toshitaka Nagao, Yuichiro Tada,ABSTRACT
Background
Optimal treatment for non‐metastatic unresectable salivary duct carcinoma (SDC) remains unclear. We compared outcomes of upfront biomarker‐targeted systemic therapy and radiotherapy.
Methods
We retrospectively analyzed the Joint SDC Study Group registry. Thirty‐one patients with centrally confirmed non‐metastatic unresectable SDC were classified by initial treatment (radiotherapy or systemic therapy). Systemic therapy included trastuzumab plus docetaxel, combined androgen blockade, or chemotherapy. Progression‐free survival (PFS) and overall survival (OS) were analyzed.
Results
Systemic therapy showed better PFS than radiotherapy (3‐year PFS 47.6% vs. 30.0%, p = 0.031) without OS difference. Trastuzumab plus docetaxel showed the highest response rate (75%) and enabled curative‐intent treatment in all cases, with the best PFS (3‐year 87.5%, p = 0.012).
Conclusions
Given the retrospective design and limited sample size, these findings should be regarded as hypothesis‐generating. An upfront trastuzumab‐based therapy followed by curative‐intent treatment may be a promising option for selected patients with HER2‐positive unresectable SDC.