Synchronous multiple primary tumors in patients with malignant lymphoma: a retrospective study

BACKGROUND: Synchronous multiple primary malignant tumors (sMPMTs) are sometimes diagnosed in patients with malignant lymphoma. We herein investigated the prognostic impact of sMPMT in lymphoma patients and the optimal treatment strategy. METHODS: Seventy-five patients with sMPMTs (5.8%) among 1285 patients with lymphoma newly diagnosed between August 2004 and April 2020 were enrolled. RESULTS: In patients with indolent lymphoma, those with sMPMTs had a worse prognosis than those without sMPMTs (5-year overall survival [OS]: 73.4% and 87.8%, respectively; P = 0.047). Among those with high and low tumor burden, the cumulative rate of death due to solid tumors was significantly higher in patients with sMPMTs than those without sMPMTs (high tumor burden: 26.7% vs. 1.6%, P < 0.001; low tumor burden: 12.7% vs. 1.0%, P = 0.003). The presence of sMPMTs did not have a significant impact on outcomes in patients with diffuse large B-cell lymphoma (DLBCL) (5-year OS: 65.4% and 66.9%, respectively; P = 0.74; 5-year progression-free survival [PFS]: 65.5% and 59.9%, respectively; P = 0.65). However, the cumulative rate of death from solid tumor in patients with sMPMTs was significantly higher than in patients without sMPMTs (5-year cumulative rate: 7.4% and 2.1%, respectively; P = 0.004). The treatment sequence did not have a significant effect on outcomes or the relative dose intensity of chemotherapy. CONCLUSIONS: In patients with indolent lymphoma, those with sMPMTs had a significantly worse prognosis than those without sMPMTs, mainly because of high mortality due to solid tumors. The presence of sMPMTs was not a significant prognostic factor in patients with DLBCL. It is important to assess the status and need for early treatment of each type of malignancy in patients with sMPMTs.