RCHOP Plus High-Dose Methotrexate As First-Line Therapy in Large B-Cell Lymphoma with Testis Involvement

Primary testicular lymphoma (PTL) and diffuse large B-cell lymphoma with secondary testicular involvement (DLBCL-T) are rare subtypes of lymphomas associated with poor prognosis and a high risk of central nervous system (CNS) relapse. The optimal CNS prophylaxis strategy for these subtypes remains uncertain. High-dose methotrexate (HD-MTX) is debated for CNS prophylaxis, but its efficacy in this setting is unknown. This study aimed to retrospectively analyze the use of HD-MTX in combination with chemotherapy (R HD-MTX CHOP) as frontline treatment for PTL and DLBCL-T and to compare the biological characteristics of these two forms of testicular involvement.

Data from patients who received R HD-MTX CHOP as first-line treatment for DLBCL-T or PTL between 2010 and 2020 were collected retrospectively. The study included 15 patients, 5 with PTL and 10 with DLBCL-T.

The overall response rate was 86%, with 73% of patients achieving complete remission. Treatment-related adverse events were generally manageable, with febrile neutropenia being the most common. Two patients experienced CNS relapse, both from the DLBCL-T subgroup, with a median time of 10.7 months from diagnosis to CNS relapse. None of the PTL patients receiving HD-MTX experienced relapse during the median follow-up of 6.08 years (Figure 1A), compared to 8/10 DLBCL-T (p=0.007).

All five PTL cases had a non-germinal center phenotype, while 7 out of 10 DLBCL-T cases were non-germinal center. One DLBCL-T case exhibited high-grade lymphoma. Myc expression was positive in 3 out of 10 patients assessed, of whom all were double expressors. Bcl-2 expression was positive in all 13 assessable patients, while Bcl-6 expression was positive in 6 patients.

Myc, Bcl-2, and Bcl-6 rearrangements were assessed in 10 patients and were present in 1 patient who was found to have triple-hit lymphoma. No other patient had double-hit lymphoma or any significant rearrangement. Polysomy of Myc, Bcl-2, and/or Bcl-6 was found in 2 patients. PDL1 expression was observed in one out of six patients analyzed, while no PD1 expression was detected.

In 8 out of 15 patients with available tissue material, next-generation sequencing using a panel targeting 43 lymphoid genes was performed. Among these 8 patients, 87% exhibited gain-of-function mutations in MYD88 (MYD88 L265P), and 62% had missense mutations in CD79B at position Y196. Multiple mutations in the PIM1 gene, a known target of aberrant somatic hypermutation, were also observed in 7 patients. Non-recurrent mutations were detected in various genes, including PRDM1, CD58, B2M, CREBBP, CIITA, CARD11, CDKN2A, EP300, CCDND3, FOXO1, IRF4, NFKBIE, and TCF3 (Figure 1B).

Ig rearrangement was analyzed in 4/9 patients with available DNA. All 4 were clonal, with distinct but mutated VH segments (sequence identity between 81 and 89%).

This study suggests that HD-MTX in combination with RCHOP chemotherapy is highly effective in preventing CNS relapse in PTL but less so in DLBCL-T. DLBCL-T had a higher risk of CNS relapse and poorer outcomes compared to PTL. Further studies are needed to determine the optimal timing and sequence of HD-MTX in DLBCL-T, as well as alternative treatment approaches.

PTL and DLBCL-T have distinct clinical presentations and responses to frontline chemotherapy with HD-MTX prophylaxis. PTL may benefit from HD-MTX in preventing relapse, while alternative treatments should be explored for DLBCL-T. Future studies should consider PTL and DLBCL-T as separate entities to better understand their characteristics and optimize treatment strategies.