Male gender is an adverse risk factor only in young patients with diffuse large B-cell lymphoma - a Swedish population-based study

Background. Diffuse large B-cell lymphoma (DLBCL) is a heterogeneous group of B-cell lymphomas. Five clinical adverse risk factors are merged into the International Prognostic Index (IPI), which is the major tool for prognostication. In contrast to Hodgkin's lymphoma, gender is not considered as an adverse risk factor for DLBCL patients. As we clinically had observed a very good survival rate in young female patients we hypothesised that there was a gender difference in survival due to the hormonal status of the patient. Material and methods. We conducted a registry-based retrospective cohort study of all Swedish DLBCL patients diagnosed between 2000 and 2013, to evaluate the impact of gender for survival from DLBCL. Results. In total, 7166 patients were included for further analysis. No survival difference was found between the genders when the entire population was analysed. However, analysis of 880 young patients of pre-menopausal age (i.e. 52 years) revealed that women had a longer survival compared to men of the same age group (p = 0.007). This was not found for patients older than menopausal age. In a relative survival multifactorial model adjusted for stage, ECOG performance status, serum lactate dehydrogenase and two or more extranodal sites, male gender was found to be an adverse risk factor for patients younger than 52 years (RR 1.51, 95% CI 1.14-1.88), but not for older patients (RR 0.99, 95% CI 0.89-1.10). Conclusion. This is one of the largest population-based studies of DLBCL presented to date. Most interestingly, we found male gender to be a significant adverse risk factor compared to fertile women whereas we found no survival differences between genders in the older sub-population.