A 62-year-old man from Delhi presents with bone pain and fatigue for 3 months. Serum calcium is 11.2 mg/dL, creatinine is 2.1 mg/dL, and hemoglobin is 9.2 g/dL. Serum protein electrophoresis shows an M-spike. Bone marrow biopsy confirms >30% plasma cells. What is the most appropriate next step in management?

Explanation

## Risk Stratification Before Treatment Initiation **Key Point:** Cytogenetic and FISH analysis of bone marrow plasma cells is mandatory BEFORE starting therapy in newly diagnosed multiple myeloma (MM) to determine prognosis and guide treatment intensity. ### Why Cytogenetics/FISH is the Next Step Once MM diagnosis is confirmed (>30% bone marrow plasma cells + CRAB criteria met), the immediate next step is **risk stratification** using: 1. **Cytogenetics (conventional karyotyping)** — identifies hyperdiploidy, translocations 2. **FISH** — detects high-risk lesions: - `t(4;14)` — poor prognosis - `t(14;16)` — poor prognosis - `del(17p)` — very high risk - `del(13q)` — intermediate risk **High-Yield:** High-risk cytogenetics (del(17p), t(4;14), t(14;16)) mandate **proteasome inhibitor (PI)–based or immunomodulatory drug (IMiD)–based induction**, whereas standard-risk disease can use various regimens. ### Management Sequence in MM ```mermaid flowchart TD A[MM diagnosis confirmed<br/>CRAB + BM plasma cells]:::outcome --> B[Cytogenetics/FISH analysis]:::action B --> C{Risk stratification}:::decision C -->|High-risk| D[PI + IMiD ± corticosteroid]:::action C -->|Standard-risk| E[Flexible induction options]:::action D --> F[Assess response at 4 cycles]:::action E --> F F --> G[Stem cell transplant consideration]:::decision ``` ### Why Other Options Are Premature | Option | Why Not Next | Correct Timing | |--------|-------------|----------------| | **Bortezomib immediately** | Cannot choose therapy without risk stratification; may over/under-treat | After FISH results | | **Hydration + allopurinol** | Supportive care is parallel, not sequential; renal impairment is part of CRAB but doesn't delay cytogenetics | Concurrent with workup | | **PET scan** | Whole-body imaging is not standard for MM staging; skeletal survey or low-dose CT suffices | Not routine in MM | **Clinical Pearl:** Renal impairment (Cr 2.1) is a CRAB criterion and does NOT delay cytogenetic testing — both proceed in parallel during the diagnostic phase. **Mnemonic — CRAB Criteria:** **C**alcium (>11.5), **R**enal insufficiency (Cr >2), **A**nemia (Hb <10), **B**one lesions (lytic). This patient has C, R, and A. [cite:Harrison 21e Ch 186]