A 58-year-old woman with newly diagnosed multiple myeloma (IgG-κ, 35% plasma cells, standard-risk cytogenetics) has completed 4 cycles of bortezomib-lenalidomide-dexamethasone induction therapy. Serum M-spike has decreased from 3.2 g/dL to 0.8 g/dL. She is 58 years old, has normal cardiac function, and is deemed fit for transplantation. What is the most appropriate next step in management?

Explanation

## Clinical Context This patient has achieved a partial response (PR) to induction therapy and is a candidate for high-dose chemotherapy with autologous stem cell transplantation (ASCT), which remains the standard of care for transplant-eligible patients with newly diagnosed MM. ## Standard-of-Care Pathway for Transplant-Eligible MM **Key Point:** ASCT is the standard consolidation therapy for transplant-eligible patients (typically age <65–70 years with adequate organ function) after achieving response to induction therapy. **High-Yield:** The MM treatment algorithm for transplant-eligible patients: 1. **Induction** (4–6 cycles) — bortezomib-based regimen (VRd, VTd, or VPd) 2. **Response assessment** — if ≥PR, proceed to ASCT 3. **ASCT** — high-dose melphalan (200 mg/m²) with stem cell reinfusion 4. **Consolidation** (optional) — 1–2 additional cycles if <CR after ASCT 5. **Maintenance** — lenalidomide ± bortezomib ± dexamethasone for 2–3 years ## Treatment Timeline ```mermaid flowchart TD A[Newly Diagnosed Transplant-Eligible MM]:::outcome --> B[Induction: 4-6 cycles VRd/VTd]:::action B --> C{Response Achieved?}:::decision C -->|No response| D[Salvage Regimen]:::action C -->|PR or better| E[Mobilize Stem Cells]:::action E --> F[High-Dose Melphalan 200 mg/m²]:::action F --> G[ASCT]:::action G --> H{CR achieved?}:::decision H -->|No| I[Consolidation: 1-2 cycles]:::action H -->|Yes| J[Maintenance Lenalidomide]:::action I --> J J --> K[Continue 2-3 years]:::action ``` **Clinical Pearl:** At age 58 with normal cardiac function and achieving PR after induction, this patient is an ideal ASCT candidate. ASCT improves overall survival (OS) and progression-free survival (PFS) compared to induction alone in transplant-eligible patients (median OS ~10 years post-ASCT vs. ~5–7 years without). **Warning:** Do NOT continue induction therapy or switch regimens if the patient is fit for ASCT — delaying transplantation reduces long-term disease control. Maintenance monotherapy (lenalidomide alone) is reserved for post-ASCT consolidation or transplant-ineligible patients. ## Rationale for Each Option | Option | Status | Rationale | |--------|--------|----------| | Lenalidomide monotherapy | **Wrong** | Appropriate *after* ASCT, not before. Continuing induction delays transplantation. | | **ASCT** | **Correct** | Standard consolidation for transplant-eligible patients with ≥PR. Improves OS/PFS. | | Thalidomide-dexamethasone | **Wrong** | Unnecessary additional induction cycles. Patient has already achieved PR and is transplant-eligible. | | Repeat bone marrow biopsy | **Wrong** | MRD assessment is prognostic but does not change immediate management. ASCT is indicated regardless of MRD status in transplant-eligible patients. | [cite:Harrison 21e Ch 110]