Radiotherapeutic Treatment of an Epidermoid Tumor in a Patient With Zanubrutinib-Treated Mantle Cell Lymphoma: The First Report of Concomitant Treatment.

Mantle cell lymphoma (MCL) is a challenging B-cell non-Hodgkin lymphoma with a poor prognosis and frequent relapses. While treatment advancements such as rituximab and Bruton tyrosine kinase inhibitors (BTKi) like ibrutinib have improved outcomes, novel treatments are continually sought. Zanubrutinib, a second-generation BTKi, promises reduced side effects due to its high selectivity and reduced off-target inhibition. This paper presents a novel case of simultaneous radiotherapy and zanubrutinib treatment in a patient with MCL. We describe a 76-year-old female with a history of MCL treated with zanubrutinib. The patient presented with a metastatic lesion in the parotid gland, which emerged from a previously treated spinocellular carcinoma. She underwent parotidectomy followed by adjuvant radiotherapy while continuing zanubrutinib. The combination was well-tolerated with minimal side effects, including grade 1 dermatitis and grade 2 mucositis, neither of which progressed significantly. Hematological parameters monitored during treatment showed delayed, transient lymphopenia and neutropenia, which resolved post-therapy. No dose adjustment was necessary. The safety and efficacy of concurrent radiotherapy and zanubrutinib treatment in MCL patients are largely unexplored in clinical literature. This case represents the first documented instance of concurrent radiotherapy and zanubrutinib treatment. Our case suggests a favorable safety profile with manageable adverse effects, contrasting with concerns about increased toxicity with other tyrosine kinase inhibitors and radiotherapy combinations. These results indicate the feasibility of this approach with minimal adverse effects. Future studies should explore the broader applicability and efficacy of this treatment strategy, focusing on long-term outcomes and the interplay between BTKi therapy and radiotherapy response.