A 62-year-old man presents with bone pain, anemia (Hb 8.5 g/dL), and elevated serum creatinine. Serum protein electrophoresis shows an M-spike of 4.2 g/dL, and bone marrow biopsy reveals 65% plasma cells. A diagnosis of newly diagnosed multiple myeloma (NDMM) is confirmed. The patient is deemed fit for autologous stem cell transplantation (ASCT). What is the drug of choice for induction therapy in this patient?

Question

Accepted Answer

D. Bortezomib-based regimen (VD or VTD). ## First-Line Induction Therapy in Newly Diagnosed Multiple Myeloma

**Key Point:** Proteasome inhibitor (PI)-based regimens, particularly bortezomib-based combinations, are the standard of care for induction therapy in newly diagnosed multiple myeloma (NDMM) eligible for ASCT.

### Current Standard Regimens

**High-Yield:** The preferred induction regimens are:
- **VD** (Bortezomib + Dexamethasone)
- **VTD** (Bortezomib + Thalidomide + Dexamethasone) — superior response rates
- **VCD** (Bortezomib + Cyclophosphamide + Dexamethasone)

### Why Bortezomib-Based Regimens?

1. **Superior response rates:** Achieve ≥VGPR (very good partial response) in 50–60% of patients
2. **Rapid disease control:** Faster reduction of paraprotein and bone marrow burden
3. **Improved progression-free survival (PFS):** Compared to historical non-PI regimens
4. **Reversible peripheral neuropathy:** Unlike thalidomide, allows continuation in most patients
5. **Proven in ASCT-eligible patients:** Optimal cytoreduction before transplantation

### Mechanism of Bortezomib

Bortezomib is a reversible 26S proteasome inhibitor that:
- Blocks NF-κB pathway activation (central to MM cell survival)
- Induces apoptosis in myeloma cells
- Overcomes drug resistance
- Has synergy with immunomodulatory drugs (IMiDs) and dexamethasone

### Comparison of Induction Options

| Regimen | Response Rate | Toxicity | ASCT Eligibility | Current Role |
|---------|---------------|----------|------------------|---------------|
| **VTD** | 50–60% ≥VGPR | Peripheral neuropathy (reversible) | Excellent | **Preferred** |
| **VD** | 40–50% ≥VGPR | Lower toxicity than VTD | Good | Alternative if frail |
| **Melphalan** | 20–30% PR | Myelosuppression | Poor (alkylating agent) | Obsolete for ASCT candidates |
| **Thalidomide** | 30–40% PR | DVT, neuropathy | Moderate | Second-line only |

**Clinical Pearl:** VTD is superior to VD in achieving deep responses (≥VGPR) before ASCT, leading to improved post-transplant outcomes. However, VD is preferred in elderly or frail patients due to lower neuropathy risk.

**Mnemonic:** **ASCT-eligible MM = PI-based induction** — Proteasome Inhibitor (bortezomib) is the backbone; add Thalidomide or Dexamethasone for synergy.

### Why Not Other Options?

- **Melphalan monotherapy:** Alkylating agent; poor response rates (20–30%); mobilization failure for ASCT; now considered obsolete for ASCT candidates.
- **Thalidomide monotherapy:** Slower response; higher DVT risk; inferior to PI-based combinations; reserved for relapsed disease or non-transplant candidates.
- **Cyclophosphamide monotherapy:** Inadequate response rates; not standard induction; used only as part of combination (e.g., VCD).

[cite:Harrison 21e Ch 191]

Answer

A. Cyclophosphamide monotherapy

Answer

B. Thalidomide monotherapy

Answer

C. Melphalan monotherapy

Explanation

First-Line Induction Therapy in Newly Diagnosed Multiple Myeloma

Current Standard Regimens

Why Bortezomib-Based Regimens?

Mechanism of Bortezomib

Comparison of Induction Options

Why Not Other Options?

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Regimen	Response Rate	Toxicity	ASCT Eligibility	Current Role
VTD	50–60% ≥VGPR	Peripheral neuropathy (reversible)	Excellent	Preferred
VD	40–50% ≥VGPR	Lower toxicity than VTD	Good	Alternative if frail
Melphalan	20–30% PR	Myelosuppression	Poor (alkylating agent)	Obsolete for ASCT candidates
Thalidomide	30–40% PR	DVT, neuropathy	Moderate	Second-line only