As an independent and rare disease, PB-DLBCL was limited to some case reports and small-sample retrospective studies in the past. It is crucial to summarize the pathological features of PB-DLBCL,to effectively predict the prognosis, and to deepen physicians' understanding of the disease. Nomogram is a statistical tool that can integrate multiple prognostic risk factors in clinic, neutralize various factors of patients and incorporate them into prognostic evaluation, and finally display them visually. Correct use of nomograms can effectively improve patient outcomes and assist clinicians in making accurate survival assessments and treatment decisions .
In this study, based on the Seer database, we used the Cox proportional hazards model to screen out risk factors and constructed a nomogram, and then used Kaplan-Meier curve to evaluate the survival of patients. The good predictive and clinical net benefit of nomogram was demonstrated by ROC curve, calibration curve, and DCA curve. As far as we know so far, this study is the first to construct a nomogram for PB-DLBCL and analyze prognostic factors.
Through Cox multivariate analysis, we learned that age, race, gender, primary site, chemotherapy, and tumor stage were risk factors associated with survival. The nomogram this study shows that PB-DLBCL is a disease with a good prognosis, and although it is highly malignant, even some elderly people can survive for a long time after the disease. This is in line with the results of some previous studies, where the 5-year survival rate of PB-DLBCL was able to exceed 70%[3, 13]. At the same time, some retrospective studies with small samples mentioned that the incidence rate of males is higher than that of females[14, 15], which is the same as our research results. In the K-M curves, we also found that OS was higher in men than in women. Age has always been an important factor affecting many malignancies, and in the study by Wang et al, it was found that patients with primary bone malignant lymphoma had a higher risk of death from OS and CSS in patients over 61 years old, up to 7 times . Although our findings also show that older patients have a higher risk of death for OS and CSS, we think this question should be analyzed comprehensively, as many older patients have poor physical condition and also contribute to increased mortality. The same is true for race. Due to the limitations of the Seer database, we included more patients who were white, which may cause data bias.
PB-DLBCL can occur in all bones of the body, with long bones and the spine being the most common. On imaging, approximately 70% show osteolytic destruction . In our study, we found that the primary site of the tumor also affected patient OS, CSS. tumor survival was significantly lower in the spine primary than in the extremity bones. In our analysis, this may be related to the compression of nerves by spinal lesions thus leading to more severe complications and reduced survival. For example: paralysis.
In recent years, many studies have been conducted on the best treatment options for PB-DLBCL. CHOP and CHOP-like regimens are commonly used for chemotherapy, and there are no clear guidelines for combination regimens. In the study by Bruno Ventre et al, patients with PB-DLBCL showed a good prognosis when receiving anthracycline-based chemotherapy regimens with or without the administration of radiotherapy regimens. In patients receiving radiotherapy, the use of larger radiation fields and doses was not associated with better outcomes. In a further combination regimen Pfreundschuh M et al. suggest that rituximab in combination with CHOP-like chemotherapy regimens improves the long-term prognosis of young patients with diffuse large B-cell lymphoma . In the Bhagavathi S et al study, the addition of rituximab increased 3-year PFS (progression-free survival) from 52% to 88%. Radiotherapy used the usual doses for non-Hodgkin's lymphoma (35-45 Gy in 1.8-2 Gy fractions), In numerous scholarly studies, it is also suggested that radiotherapy should only be used as a consolidation option for treatment . However, in the present study, we conclude that surgical treatment is not a factor affecting patient survival. It is also mentioned in some studies that surgery does not seem to be a necessary option for patients with PB-DLBCL [12, 21]. With the progress of chemotherapy and radiotherapy, most surgical operations are used to clarify the nature of lesions.
Of course, there are some limitations in our current study. First, we only used the Seer database and did not apply information from other databases for external validation. Finally, the SEER database lacks some important information, such as disease progression, comorbidities, and complications, as well as specific information on radiotherapy and chemotherapy. This lack of information is also the direction of our future research. However, these defects did not affect the results obtained in this study. Although these factors made the study imperfect, we evaluated the impact of various factors on the survival of patients with PB-DLBCL, and the line graphs were able to help clinicians predict the prognosis of their patients.