Ionizing radiation including I131 might produce chromosomal translocation, causing hematologic malignancy. The incidence of leukemia following radioactive iodine treatment for thyroid cancer has been reported to be approximately 0.1 to 2.0% in Western countries, whereas fewer cases have been reported in Korea. We hereby report four cases of secondary hematologic malignancy, who received iodine therapy for thyroid cancer after thyroidectomy: two cases of acute lymphoblastic leukemia with t(9;22)(q34;q11.2), a case of MDS with 5q deletion, and a case of MDS with normal karyotype. Three cases of hematologic malignancy have developed after cumulative dosage of less than 800 mCi. The treatment intervals in two cases were less than 12 months, and the other two cases had I131 therapy only once. Assessment of causality using the Naranjo probability scale for adverse drug reactions showed that a 'possible' relationship existed between the use of I131 and secondary hematologic malignancy in all of the four cases in this report.
Adult ; Chromosomes, Human, Pair 22 ; Chromosomes, Human, Pair 5 ; Chromosomes, Human, Pair 9 ; Female ; Gene Deletion ; Hematologic Neoplasms/*diagnosis/genetics ; Humans ; Iodine Radioisotopes/*adverse effects/therapeutic use ; Leukemia, Radiation-Induced/*diagnosis/etiology ; Middle Aged ; Myelodysplastic Syndromes/diagnosis/genetics ; Neoplasms, Second Primary/*diagnosis/genetics ; Precursor Cell Lymphoblastic Leukemia-Lymphoma/diagnosis/genetics ; Thyroid Neoplasms/*radiotherapy ; Thyroidectomy ; Translocation, Genetic

BACKGROUND: Therapy-related myeloid neoplasms (t-MN) occur as late complications of cytotoxic therapy. This study reviewed clinical and cytogenetic characteristics of patients with t-MN at a single institution in Korea. METHODS: The study subjects included 39 consecutive patients diagnosed with t-MN. Each subject's clinical history of previous diseases, treatments, and laboratory data was reviewed, including cytogenetics. The primary diagnosis was hematologic malignancy in 14 patients and solid tumor in 25 patients. RESULTS: Therapy-related acute myeloid leukemia (t-AML, 66.7%) was found to be more common than therapy-related myelodysplastic syndrome (t-MDS). Primary hematologic malignancies that were commonly implicated included mature B-cell neoplasm and acute leukemia. Breast cancer was the most common primary solid tumor. The mean time interval from cytotoxic therapy initiation to t-MN detection was 49 months. Chromosomal aberrations were observed in 35 patients, and loss of chromosome 5, 7, or both accounted for 41% of all cases. Balanced rearrangements occurred in 13 patients; these patients showed shorter latency intervals (mean, 38 months) than patients with loss of chromosome 5 or 7 (mean, 61 months). CONCLUSIONS: In this study, we determined the clinical and cytogenetic characteristics of Korean patients with t-MN. Although our results were generally consistent with those of previous reports, we found that t-MN resulting from de novo leukemia was common and that t-AML was more common than t-MDS at presentation. Multi-institutional studies involving a larger number of patients and additional parameters are required to investigate the epidemiology, genetic predisposition, and survival rate of t-MN in Korea.
Adolescent ; Adult ; Aged ; Antineoplastic Agents/*adverse effects/therapeutic use ; Asian Continental Ancestry Group ; Bone Marrow/pathology ; Breast Neoplasms/drug therapy/pathology/radiotherapy ; Child ; Child, Preschool ; Chromosome Aberrations ; Chromosomes, Human, Pair 5 ; Chromosomes, Human, Pair 7 ; Female ; Hematologic Neoplasms/drug therapy/pathology/radiotherapy ; Humans ; Karyotyping ; Leukemia, Myeloid, Acute/*diagnosis/etiology/genetics ; Male ; Middle Aged ; Myelodysplastic Syndromes/*diagnosis/etiology/genetics ; Neoplasms, Second Primary/*diagnosis/etiology/genetics ; Republic of Korea ; Young Adult