Primary Bone Lymphoma. A Single Center Experience.

Introduction. Primary Bone Lymphomas [PBL] are rare extranodal non Hodgkin’s Lymphomas [NHL] constituting about 5% of all extranodal NHL. In this study we present our experience from a retrospective analysis of patients with PBL; we have assessed the patient characteristics, response to therapy and outcome.

Patients - Methods. From a population of 600 newly diagnosed patients with NHL who have been registered to our Unit between 1990 and 2004, 18 [ 3% ] have been classified as PBL. Apart from patient characteristics and clinical course, 12 cases were studied with immunohistochemistry for expression of antigens associated with different stages of B-cell differentiation. The median age of the patients [12 men, 6 women, M/F ratio 2/1] was 54 years (range 32 – 83). The stage of the disease was evaluated as I in 12 patients (66 %), II in one (6%), and IV in five patients (28%). The histology was that of a diffuse large -B-cell lymphoma in 17 cases [94%] while one patient [6%] had lymphoplasmacytoid lymphoma. The most common site of involvement was the axial skeleton (13/18, 72%), followed by the long bones of the extremities (5/18, 27%). All studied tumors revealed a germinal center [ G-C] immunophenotype signature [bcl−6 +], but only 4 of 12 [33%] confirmed their G-C origin [bcl-6+CD10+].

Results: Sixteen patients were treated with an anthracycline based chemotherapy regimen with [14] or without [2] radiotherapy [RT]. Only one patient was treated with RT alone, while one patient denied treatment. Fifteen patients (88%) achieved complete remission, one (6%) partial remission, and one patient (6%) had progressive disease to first line therapy with a CHOP-like regimen. Five patients (30%) experienced relapse; in three cases the relapses involved the CNS. Finally, 16 patients remain alive: 14 in CR [10 (60%) in 1^st, 4 (23%) in 2^nd CR], and one (6%) with active disease. Two patients (11%) have died, both with CNS disease. One patient survives without recieving treatment. With a median follow-up time of 47 months (range 8– 150), the 6 year actuarial overall and disease free survival was 72% and 52% respectively.

Conclusions: PBL are rare extranodal NHL. They mostly involve the bones of the axial skeleton. The vast majority of them present with a germinal center immunophenotypic profile. The response rate is high (88%). However, the disease recurs in one third of the cases, most often in the CNS.