A case of treatment-related myelodysplastic syndrome in the early stage after radiotherapy in a patient with cancer of the oral floor

Therapy-related myelodysplastic syndrome (t-MDS) is a rare but potentially fatal adverse event caused by chemotherapy or radiotherapy. We report a case of t-MDS diagnosed 8 months after radiotherapy for recurrent carcinoma of the floor of the mouth and cervical lymph node metastases after surgical treatment. A 74-year-old man visited our department with the chief complaint of pain in the lower part of the tongue. Tumor resection and right radical neck dissection (RND) were performed based on the diagnosis of carcinoma of the floor of the mouth (cT1N2bM0). A computed tomography scan at 10 months postoperatively showed metastatic lymph nodes in the left neck, right hyoid bone, right parotid subpolar, and anterior trachea. Therefore, the patient underwent left RND and excision of the right hyoid bone, subpolar right parotid and anterior tracheal metastatic lymph nodes. Postoperative radiation therapy (70 Gy) was administered to the neck bilaterally. An upper gastrointestinal examination revealed a carcinoma in situ in the lower esophagus, and endoscopic submucosal dissection of the esophagus was performed. He had pancytopenia preoperatively, which progressed postoperatively; therefore, a bone marrow examination was performed to rule out a hematological malignancy. Bone marrow smear and flow cytometric analyses indicated the development of t-MDS. He received supportive transfusion therapy but died 8 months after the diagnosis of t-MDS. During post-treatment follow-up, clinicians should be aware of t-MSD, in addition to cancer recurrence and metastasis.