[Characteristics and survival analysis of 60 cases of primary diffuse large B-cell lymphoma of the breast]

Objective: To investigate the characteristics and prognostic factors of primary breast diffuse large B-cell lymphoma (PB-DLBCL) . Methods: Clinical data on 60 patients with PB-DLBCL admitted to Ruijin Hospital, affiliated with Shanghai Jiao Tong University School of Medicine, from November 2013 to September 2022, were respectively collected, and survival and prognostic analyses were conducted. Among them, 44 patients underwent targeted sequencing (of 55 lymphoma-related genes) to assess the gene mutation status and its impact on survival outcomes. Results: All 60 patients with PB-DLBCL were female. The median age was 56.5 years (49.0, 61.0). The overall 5-year progression-free survival (PFS) rate was 66.5% (95% CI: 51.0% -86.7% ), and the 5-year overall survival (OS) rate was 90.6% (95% CI: 80.5% -100.0% ). After one-line treatment, 96.7% (58 patients) achieved complete remission (CR). The results of univariate analysis showed that elevated LDH (HR=3.380, 95% CI: 1.160-9.791, P=0.025) and nongerminal center B-cell (non-GCB) type (HR=3.560, 95% CI: 1.000-12.700, P=0.049) were adverse prognostic factors for PFS in patients with PB-DLBCL, whereas elevated LDH (HR=6.212, 95% CI: 1.150-38.941, P=0.034) was an adverse prognostic factor for OS. Multivariate analysis did not identify independent adverse prognostic factors for PFS in patients with PB-DLBCL. Targeted sequencing results showed that the mutation frequencies of PIM1, MYD88, KMT2D, CD79B, DTX1, and MPEG1 were >20%. Log-rank test revealed that patients with PIM1 mutations (n=27) had a significantly lower 5-year PFS rate compared to those without mutations (n=17) [59.8% (95% CI: 39.7% -90.0% ) vs 80.7% (95% CI: 58.3% -100% ), P=0.019]. Regarding MPEG1, patients without mutations (n=34) exhibited a significantly lower 5-year PFS rate than those with mutations (n=10) [59.4% (95% CI: 41.0% -86.1% ) vs 100%, P=0.048]. For DTX1, patients with mutations (n=10) had a significantly lower 5-year OS rate than those without mutations (n=34) [48.0% (95% CI: 18.8% -100% ) vs 100%, P=0.004]. Similarly, patients with MYD88 mutations (n=21) showed a significantly lower 5-year OS rate than those without mutations (n=23) [75.4% (95% CI: 52.9% -100% ) vs 100%, P=0.004]. Conclusion: The 5-year OS rate of PB-DLBCL is relatively high, whereas the PFS rate is relatively low. Elevated LDH levels and having the non-GCB type are adverse prognostic factors affecting patient survival. The mutation frequencies of PIM1, MYD88, KMT2D, CD79B, DTX1, and MPEG1 are higher in PB-DLBCL. Patients with mutations in PIM1, MYD88, and DTX1 have a poor prognosis, whereas those with MPEG1 mutations have a favorable prognosis.