What is the recommended salvage therapy regimen, dosing schedule, and minimum number of cycles for primary mediastinal B‑cell lymphoma (PMBCL) before autologous stem‑cell transplantation?

Salvage Therapy for Relapsed/Refractory Primary Mediastinal B-Cell Lymphoma (PMBCL)

For relapsed/refractory PMBCL after frontline DA-EPOCH-R, use 2-3 cycles of platinum-based salvage chemotherapy (R-DHAP, R-ICE, or R-IGEV) followed by high-dose chemotherapy and autologous stem cell transplantation (ASCT) in eligible patients, with the goal of achieving complete metabolic response (negative PET) before transplant.

Treatment Algorithm

Initial Salvage Approach

The evidence for PMBCL-specific salvage therapy is limited, but the most recent data from 2026 provides critical guidance 1. While general DLBCL guidelines recommend salvage regimens such as R-DHAP (rituximab, cisplatin, cytarabine, dexamethasone), R-ICE (rituximab, ifosfamide, carboplatin, etoposide), or R-IGEV (rituximab, ifosfamide, gemcitabine, vinorelbine) 2, 3, PMBCL behaves differently than systemic DLBCL and requires specific consideration.

Key distinction for PMBCL: Patients with refractory disease (relapsing <6 months after frontline DA-EPOCH-R) have significantly worse outcomes compared to those with true relapsed disease (>6 months):

• Refractory patients: 48% overall response rate, 19% complete remission rate, 30% 2-year PFS
• Relapsed patients: 83% overall response rate, 44% complete remission rate, 69% 2-year PFS 1

Number of Salvage Cycles

Administer 2-3 cycles of salvage chemotherapy before proceeding to ASCT 4, 3. The guideline evidence consistently supports this approach:

• Response evaluation should occur after 2-4 cycles of salvage therapy, specifically before stem cell collection 3
• A fourth cycle may be considered only if transplantation must be delayed and response needs to be maintained 5

Critical Pre-Transplant Goal

Achieving a negative PET scan (complete metabolic response) before ASCT is the primary objective of salvage therapy, as this strongly predicts improved clinical outcomes 4. Among PMBCL patients who achieved complete remission before ASCT, there were zero relapses in the largest retrospective analysis to date 1.

Transplant Outcomes

For PMBCL patients who successfully undergo ASCT after salvage therapy:

• 5-year progression-free survival: 85%
• 5-year overall survival: 88%
• Patients in complete remission pre-ASCT had no relapses 1

This represents excellent outcomes and validates the aggressive approach to achieving complete response before transplant.

Specific Regimen Selection

While no head-to-head comparisons exist for PMBCL specifically, the following regimens are recommended based on DLBCL guidelines 2, 3:

First-line salvage options:

• R-DHAP (rituximab 375 mg/m², cisplatin, high-dose cytarabine, dexamethasone)
• R-ICE (rituximab 375 mg/m², ifosfamide, carboplatin, etoposide)
• R-IGEV (rituximab, ifosfamide, gemcitabine, vinorelbine)

These regimens showed no significant outcome differences in Hodgkin lymphoma salvage 4, and the choice should be based on:

• Prior anthracycline cumulative dose (cardiac function assessment required if further anthracyclines planned) 3
• Renal function (avoid cisplatin if impaired)
• Patient age and performance status

Conditioning Regimen for ASCT

BEAM (carmustine, etoposide, cytarabine, melphalan) remains the most frequently used high-dose conditioning regimen 4, 2, 6. Alternative regimens include:

• BeEAM (bendamustine-based modification)
• GBC/GBM (gemcitabine-based regimens)

These alternatives may offer reduced toxicity while maintaining efficacy 6.

Critical Pitfalls and Caveats

Refractory Disease Challenge

The 2026 data reveals that refractory PMBCL (relapse <6 months post-DA-EPOCH-R) has particularly poor outcomes with conventional salvage approaches 1. For these patients:

• Consider clinical trial enrollment as first priority
• CAR T-cell therapy or bispecific antibodies should be considered early if available 7
• Standard salvage chemotherapy achieves CR in only 19% of refractory patients 1

Stem Cell Mobilization

• Mobilize stem cells after the first or second cycle of salvage chemotherapy unless bone marrow was involved at relapse 5
• Use G-CSF with or without plerixafor for mobilization
• Target collection: ≥2×10⁶ CD34+ cells/kg 8

Radiotherapy Considerations

The role of radiotherapy before ASCT is not well-defined 4. Consider involved-field radiotherapy only for:

• Single PET-positive lymph nodes after salvage therapy 4
• Residual radiographic disease at bulky sites

Avoid thoracic radiotherapy within 50 days before ASCT due to high post-transplant mortality risk 5.

Age and Fitness Criteria

Standard eligibility for ASCT:

• Age <65-70 years
• No major organ dysfunction
• Adequate performance status 2, 3

Alternative Approaches for Transplant-Ineligible Patients

For patients unsuitable for ASCT, emerging options include 7, 9:

• CAR T-cell therapy (increasingly used in second-line setting)
• Bispecific antibodies
• Immune checkpoint inhibitors (given 9p24.1 amplification in PMBCL)
• Brentuximab vedotin (if CD30-positive)

The 2025 EHA guidelines suggest CAR T-cells as gold standard for second-line therapy in patients refractory or relapsing within <1 year 7, which applies to the majority of PMBCL relapses given the poor outcomes in this population 1.