## 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]
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