# Complete Response in Salivary Duct Carcinoma Ex Pleomorphic Adenoma With Upfront Combination of Trastuzumab and Chemo-Hormonal Therapy

## TL;DR

A rare aggressive cancer showed a complete response to a combination of trastuzumab, hormone therapy, and chemotherapy.

## Contribution

A novel treatment combination achieved a durable complete response in a rare and aggressive salivary duct carcinoma.

## Key findings

- A 48-year-old male with advanced SDC ex pleomorphic adenoma achieved complete response after treatment.
- Combination therapy included trastuzumab, CAB, and docetaxel, showing durable results over 17 months.
- The case highlights a potential treatment strategy for rare cancers where large studies are impractical.

## Abstract

Salivary duct carcinoma (SDC) is one of the rarest malignancies. It can arise de novo or from pre-existing pleomorphic adenoma (carcinoma ex pleomorphic adenoma - CXPA) and can be very aggressive.

Here, we present one such case of a 48-year-old male with relapsed, widely invasive SDC ex pleomorphic adenoma of the parotid that was locally advanced with intracranial extension that was refractory to chemo-radiation. Immunohistochemistry confirmed positivity for human epidermal growth factor receptor-2 (HER2) and androgen receptor (AR). He was started on a combination of trastuzumab, Combined Androgen Blockade (CAB) with leuprolide and bicalutamide, and docetaxel. Follow-up imaging at three months and nine months from treatment initiation demonstrated a complete response, ongoing at 17 months at follow-up. The upfront combination of anti-HER2 therapy, CAB, and chemotherapy resulted in a durable complete response in an aggressive disease.

The result obtained from our experience provides valuable insight into the management of a rare and treatment-resistant entity, where large prospective studies without heterogeneity are not possible.