TRASTUZUMAB-BASED THERAPY FOR METASTATIC SALIVARY DUCT CARCINOMA OVER-EXPRESSING HER2: CASE REPORT OF A COMPLETE RESPONSE

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Abstract

Background

Salivary duct carcinoma (SDC) is an aggressive tumor with high mortality. Except surgical operation and radiotherapy, there is no consensus on the role of optimal treatment. Histopathologically, SDC is morphologically similar to invasive breast carcinoma, and over-expression for HER2 has been also reported in SDC in recent years.

Case

We present a 35 years-old woman diagnosed with intraoral SDC in the maxillary gingiva. Eight months after completion of surgery and adjuvant radiotherapy, she developed local recurrence. In spite of additional surgery, CyberKife radiosurgery, proton beam therapy, also chemotherapy (TS-1) and alternative therapy, she developed multiple metastases and a massive local recurrence. Since she had been resistance to various treatment, the excised specimen had evaluated again. Immunohistochemistry analysis showed strong (3+) overexpression for HER2.

Result

After institutional review board and cancer board approved consents of off-label, she received concomitant chemotherapy with trastuzumab (8 mg/kg dose-loading and 6 mg/kg) and docetaxel (75 mg/m2) every 21 days. The tumor was reduced quickly and complete clinical response was attained seven months after treatment initialized.

Conclusions

SDC is uncommon in the salivary gland neoplasm and there are limited data because of their rarity. As histologically resembled, SDC appears to be strongly overexpress HER2 at much higher frequency than breast carcinoma. We treated an advanced case of SDC with trastuzumab and attained a complete clinical response. Trastuzumab-based therapy might be an effective regimen for advanced SDC over-expressing HER2. Recently, trasutuzmab plus chemotherapy also improved survival in patients with HER2 positive gastric cancer compared with chemotherapy alone. In view of validity having been shown also in the HER2 positive gastric cancer moreover breast cancer, drug development might be advanced to biomarker oriented from now on regardless the kind of cancer.

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