Primary thyroid lymphoma - A retrospective analysis of prognostic factors and treatment outcome for localized intermediate and high grade lymphoma

Non-Hodgkin's lymphoma presenting in the thyroid gland is uncommon. A revie w of the King Faisal Specialist Hospital and Research Centre (KFSH & RC) ex perience was performed to assess treatment outcome and prognostic factors i n this rare extranodal presentation of localized lymphoma. Sixty patients t reated at KFSH & RC between 1975 and 1995 were identified, and their record s were reviewed retrospectively. Eight patients who had stage III or IV dis ease, low grade, or did not complete their prescribed treatment were exclud ed from the study. There were 38 female and 14 male patients with a median age of 59.5 years at the time of diagnosis (range: 10-87 years). Thirty fiv e of the 52 patients underwent diagnostic partial or total thyroidectomy at other institutions based on a preoperative assumption of thyroid carcinoma . All 52 patients had non-Hodgkin's lymphoma of intermediate (94%) or high (6%) grade. Detailed staging was carried out in all patients; 16 patients ( 31%) had disease confined to the thyroid gland (stage IE), whereas 36 (69%) had associated disease in cervical lymph nodes and/or the mediastinum (sta ge IIE) disease. All patients were treated with curative intent. A total of 18 patients (35%) were treated with a single-modality treatment-radiothera py alone in 2, chemotherapy alone in 13, and surgery alone in the remaining 3 patients. The majority of patients (34/52; 65%) were treated with a comb ined-modality approach. The overall relapse-free survival (RFS) and overall survival (OS) at 5 years were 72% and 88%, respectively. There were no sig nificant differences in outcome between those treated with single-modality and those with combined-modality therapy. A univariate analysis showed that the presence of mediastinal lymph node involvement was the most important prognostic factor affecting both RFS and OS. Patients with Hashimoto thyroi ditis and without "B" symptoms were found to have a significantly higher RF S without influence on the OS. However, patients who had a good performance status (PS) of 0, 1, and 2 were found to have a significantly higher overa ll survival in comparison to those with poor performance status. Age, sex, stage, histology, lactic acid dehydrogenase level, tumor bulk, and the trea tment modality were not found to correlate with RFS or OS. Mediastinal invo lvement and PS were found to be the most important independent prognostic f actors influencing RFS and OS.