Primary bone lymphoma: a new and detailed characterization of 28 patients in a single-institution study.

BACKGROUND: The incidence of primary bone lymphoma (PBL) is so rare that many of its aspects remain unknown. A number of studies have been reported from Western countries, but only a few reports are available from Asia.

METHODS: We retrospectively analyzed 28 consecutive patients diagnosed with PBL initially treated at our hospital between 1995 and 2004. All patients underwent chemotherapy with half receiving radiotherapy as their initial treatment. A log-rank test was used in a univariate analysis to identify factors affecting overall survival.

RESULTS: Fifteen (54%) patients were male and 13 (46%) female with a median age of 47 (range: 5-81). Although 19 (68%) patients had diffuse large B-cell lymphoma (DLBCL), other histopathological subtypes (three B-lymphoblastic lymphoma, two anaplastic large cell lymphoma, two indolent B-cell lymphoma, one NK/T-cell lymphoma (NTCL) and one Hodgkin lymphoma) were also included. The pelvis was the most frequently involved site (54%). While 68% of patients had stage IV disease, none of them showed bone marrow involvement at their initial diagnosis. Despite 61% high intermediate-risk and high-risk patients based on the International Prognostic Index, the estimated 3-year overall and progression-free survival rates were 84% and 77%, respectively. Only 'histopathological subtype (immunoblastic variant of DLBCL or NTCL versus others)' and 'response to initial treatment (progression versus remission)' were factors significantly affecting overall survival.

CONCLUSIONS: Although the total number of patients was relatively small, the detailed clinical data analyses presented here revealed several new characteristics of PBL and some aspects that may be unique to Japanese patients.