The clinical features, management and prognosis of primary and secondary indolent lymphoma of the bone: a retrospective study of the International Extranodal Lymphoma Study Group (IELSG #14 study).

Indolent lymphomas primarily involving the skeleton (iPBL) represent < 1% of all primary bone lymphomas. The management and prognosis have not been previously described. Patients with primary and secondary iPBL were selected from an international database of 499 patients with a histopathological diagnosis of non-Hodgkin lymphoma and skeleton involvement, and clinical features, management and prognosis were analyzed. Twenty-six (5%) patients had an iPBL. Ten patients had small lymphocytic lymphoma, 10 had follicular lymphoma and six had lymphoplasmacytic lymphoma. Eleven patients had limited stage and 15 had advanced disease. The overall response rate was 73% (95% confidence interval [CI] = 57-89%). Median follow-up was 58 months, and the 5- and 10-year progression-free survival (PFS) rates were 37 ± 10% and 25 ± 12%, respectively. Nine patients are alive, with 5- and 10-year overall survival (OS) rates of 46 ± 10% and 29 ± 11%, respectively. Patients with small lymphocytic lymphoma showed significantly better outcome than patients with follicular lymphoma. Performance status and stage of disease were independently associated with OS. The prognosis of patients with primary bone lymphoplasmacytic or follicular lymphoma was less favorable.