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 review of the King Faisal Specialist Hospital and Research Centre (KFSH & RC) experience was performed to assess treatment outcome and prognostic factors in this rare extranodal presentation of localized lymphoma. Sixty patients treated at KFSH & RC between 1975 and 1995 were identified, and their records were reviewed retrospectively. Eight patients who had stage III or IV disease, low grade, or did not complete their prescribed treatment were excluded 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-five 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 (stage IIE) disease. All patients were treated with curative intent. A total of 18 patients (35%) were treated with a single-modality treatment--radiotherapy 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 combined-modality approach. The overall relapse-free survival (RFS) and overall survival (OS) at 5 years were 72% and 88%, respectively. There were no significant 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 thyroiditis and without "B" symptoms were found to have a significantly higher RFS 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 overall survival in comparison to those with poor performance status. Age, sex, stage, histology, lactic acid dehydrogenase level, tumor bulk, and the treatment modality were not found to correlate with RFS or OS. Mediastinal involvement and PS were found to be the most important independent prognostic factors influencing RFS and OS.