The long-term survival of a thymic carcinoma patient treated with S-1: a case report and literature review
A 73-year-old Japanese man was referred to our hospital in October 2008 because of an abnormal shadow in the mediastinum on chest X-ray. His medical history was unremarkable, and he had taken no medications. He had smoked 50 pack-years. Physical examination revealed no significant abnormalities except for his clubbed fingers. Laboratory findings were within normal ranges, except the serum cytokeratin 19 fragment (CYFRA) level of 16.6 ng/mL (normal range, 0–3.5 ng/mL). A subsequent computed tomography (CT) scan revealed a mass lesion in the anterior mediastinum involving the superior vena cava, with multiple pleural dissemination. Whole body 18F-fluorodeoxy glucose positron emission tomography (FDG-PET) showed strong activity in the anterior mediastinal lesions (7.1 maximum standardized uptake values) and the multiple pleural ones. A CT-guided needle biopsy of the main lesion in the anterior mediastinum was performed. The pathological diagnosis was squamous cell thymic carcinoma. Immunohistochemically, the tumor cells showed positive staining for CD117 (c-kit) and CD5, and negative staining for terminal deoxynucleotidyl transferase (TdT) in the lymphocytes in the tumor. The Ki-67 (MIB-1) index was more than 30%. The results of immunohistochemical analysis supported a diagnosis of thymic carcinoma. Immunohistochemical staining for the enzymes related to 5-FU metabolism was also performed: thymidylate synthase (TS) was strongly positive, dihydropyrimidine dehydrogenase (DPD) was weakly positive, and orotate phosphoribosyltransferase (OPRT) was not stained ().\nSince he had advanced stage disease (Masaoka–Koga staging system, IVa), he was treated with three cycles of first-line chemotherapy, including cisplatin (50 mg/m2) on day 1, doxorubicin (40 mg/m2) on day 1, vincristine (0.6 mg/m2) on day 3, and cyclophosphamide (700 mg/m2) on day 4, every 4 weeks from December 2008 to February 2009. After three cycles of chemotherapy, stable disease (SD) was observed. Additional radiotherapy (50 Gy) was given as multimodality treatment for the main anterior mediastinal lesion from March to April 2009. He had SD after the radiotherapy, and the serum CYFRA level was 14.0 ng/mL. In July 2009, the serum CYFRA level increased suddenly (34.7 ng/mL). Therefore, second-line chemotherapy with S-1 (50 mg/m2) twice a day was given. The administration of S-1 was conducted as follows: 2 weeks of administration and 1 week of withdrawal of S-1. The S-1 therapy was effective, since the main tumor and the pleural dissemination showed remarkable reduction in their sizes, and the serum CYFRA level became 1.7 ng/mL after two cycles of chemotherapy in September 2009 ( and ). The hematologic adverse events (AEs) were as follows: leukopenia (grade 3), neutropenia (grade 2), anemia (grade 2), and thrombocytopenia (grade 1), with no febrile neutropenia. There were no non-hematologic grade 3 or 4 AEs. The patient has been continued on S-1 without disease progression or impairment of his quality of life (QOL) for more than 4 years.