4CPS-106 Novel approach to an uncommon case: acinic cell carcinoma of the salivary glands treated with lenvatinib

<h3>Background and Importance</h3> Acinic cell carcinoma (ACC) of the salivary glands is an extremely rare tumour, representing 6–8% of salivary carcinomas. Surgical excision is the main treatment for low-grade tumours; however, treatment in high-grade malignancies remains unclear, with most cases managed through surgery and adjuvant radiotherapy. The average recurrence rate is around 35%, commonly involving cervical lymph nodes and lungs <h3>Aim and Objectives</h3> The objective of this study is to evaluate the efficacy and safety of lenvatinib used off-label for metastatic ACC. <h3>Material and Methods</h3> A 65-year-old male patient was diagnosed with localised ACC in March 2015 and underwent radical parotidectomy and petrosectomy followed by radiotherapy. After 6 years without symptoms, a biopsy confirmed metastasis in January 2021, and carboplatin-paclitaxel was chosen for its lower toxicity. In September 2021, the patient experienced new pleural progression and initiated treatment with lenvatinib. <h3>Results</h3> The patient continued with lenvatinib for 1 year at a daily dose of 24 mg, with breaks on weekends, and tolerated it except for grade 1 mucositis and diarrhoea. In September 2022, pleural and pericardial relapse prompted next-generation sequencing, but preserved MLH1, PMS2, MSH2, and MSH6 made the patient unsuitable for immunotherapy, leading to doxorubicin initiation. As of April 2024, 18 months after starting doxorubicin, the patient remains stable. <h3>Conclusion and Relevance</h3> Lenvatinib was chosen based on current evidence, which reports mutations in 76% of ACC patients for vascular endothelial growth factor (VEGF) and in 90% of the c-kit receptor. Lenvatinib is a tyrosine kinase inhibitor (TKI) that inhibits VEGF receptors and other TKIs, justifying its use. After a review, we found only one published Phase II clinical trial that showed a time to event of 8 months, while this patient achieved 12 months. This clinical case represents one of the few real-world evidences published on the treatment of ACC with lenvatinib. Through this treatment, the patient has achieved a new therapeutic line that has significantly contributed to an optimal quality of life. <h3>References and/or Acknowledgements</h3> <h3>Conflict of Interest</h3> No conflict of interest