PBL is a rare subtype of NHL. Therefore, owing to its low incidence rates, specific therapeutic guidelines for PBL treatment have not yet been established. Therapeutic options include surgery, RT, chemotherapy, or chemoradiation. Prior to the use of chemotherapy as treatment, PBL was treated using radiation or surgery. However, the role of surgery in PBL should be limited to biopsies, bone fracture repair, or disease control in selected patients with low-grade lymphomas who cannot tolerate additional therapeutic interventions because of other medical conditions.
In the 1960s, RT was established as the standard PBL treatment method, with reported cure rates ranging from 44% to 63% [13
]. However, despite relatively high CR rates following RT alone, relapse in regions outside the radiation field was commonly observed. Therefore, although radiation provides excellent local control, systemic therapy is needed to prevent recurrence outside the radiation portal [13
While some studies have established that combined modality treatment consisting of chemotherapy and RT provides a superior outcome to RT alone [16
], other studies have failed to demonstrate such a significant advantage of combined modality over RT alone [1
]. Recently, clinical outcomes of patients treated with immunochemotherapy such as rituximab have been reported [5
]. However, no study has yet reported the detailed treatment response characteristics of PBL patients treated with rituximab-containing regimens in Korea. In the present study, we observed that most PBL cases characteristically exhibited male predominance and had a younger median age (40 years) than nodal DLBCL cases [17
], which is consistent with previously published studies. On the other hand, previous reports had established that the most common site of involvement was the femur, followed by the pelvis, fibular or tibia, humerus, and spine, in descending order of frequency. However, according to our study, the pelvic bone was the most common involvement site [1
It is difficult to diagnose PBL and monitor response to treatment using simple imaging techniques such as radiography. Indeed, initial radiographs of patients with PBL may sometimes appear normal, while subsequent examination using bone scans or MRI would detect abnormalities. Therefore, conventional radiography has limited value in the diagnosis of PBL. Moreover, gallium scans, MRI, and positron emission tomography may falsely indicate activity following therapy due to bone remodeling [4
], which further complicates the assessment of treatment response. Previous studies have associated certain factors with the survival rates of patients with PBL. The number of bones involved (single vs. multiple) has been established as the main prognostic factor and was demonstrated as such in a large-scale study (422 patients) conducted by Ostrowski et al. [19
] In addition, Ramadan et al. and Catlett et al. [2
] demonstrated the association of high IPI scores with significantly worse patient outcomes. In the present study, our results confirm that the number of bones involved significantly affects the OS rates (P
=0.089, ), which is consistent with previous observations.
The effects of different treatment modalities on patients with PBL have not been determined. However, several studies have established that chemotherapy is essential for successful treatment of PBL [21
]. Moreover, Alencar et al. suggested that the addition of rituximab to chemotherapy regimens has a beneficial effect on the survival of patients with PBL [5
]. However, our results showed that the addition of rituximab to the treatment regimen did not significantly affect the OS of patients who underwent chemotherapy alone or the OS of patients who were given a combined modality treatment of chemotherapy and RT. Furthermore, our results demonstrated that the Ann Arbor stage, ECOG performance status, and IPI score were not associated with patient outcomes, which is consistent with the Miami University report [5
Our study has several limitations. First, the small number of patients included in the study made it difficult to achieve statistically significant results. Second, the retrospective nature of our analysis compromised the analysis of different clinical outcomes between the subgroups. This study faced the inherent challenges of studying such a rare disease. Nevertheless, to our knowledge, this is the first study that investigates the role of immunochemotherapy in the treatment of PBL patients in Korea. Moreover, it is among the largest case series studies on PBL that have ever been conducted. While this study failed to demonstrate the beneficial effects of supplementing standard chemotherapy regimens with either RT or rituximab, it confirmed that conventional cytotoxic chemotherapy is a successful treatment option for patients with PBL. Further investigation is required to characterize the role of immunochemotherapy in treating patients with PBL.