Multiple Myeloma (Plasma Cell Neoplasm): Symptoms, Staging and Treatment — Overview, Diagnosis & Treatment Options | MyMedicPlus

Multiple myeloma (MM) is a malignant clonal proliferation of plasma cells in the bone marrow, accounting for 10% of hematological malignancies and approximately 1–2% of all cancers. Malignant plasma cells accumulate in the marrow, producing a monoclonal immunoglobulin (M-protein or paraprotein) detectable on serum or urine protein electrophoresis, and causing end-organ damage through direct marrow infiltration, osteolytic bone disease, and renal toxicity. The disease spectrum ranges from the precursor state of monoclonal gammopathy of undetermined significance (MGUS) — progressing to smoldering myeloma (SMM) and ultimately to active myeloma. Approximately 35,000 new cases are diagnosed annually in the United States; median age at diagnosis is 65 years, though 10% of patients are under 50. The revised International Staging System (R-ISS) stratifies patients into three prognostic stages based on serum beta-2 microglobulin, albumin, LDH, and cytogenetics. Median overall survival with current therapy is 6–8 years for all stages combined, with ongoing improvements as quadruplet regimens and novel agents enter practice.

Multiple myeloma arises from a sequence of genomic events in a single plasma cell clone. Two primary molecular pathways are recognized: hyperdiploid myeloma (non-random gains of odd-numbered chromosomes 3, 5, 7, 9, 11, 15, 19, 21) and non-hyperdiploid myeloma (IgH translocations: t(11;14), t(4;14), t(14;16), t(14;20)). Secondary genomic events (RAS mutations, MYC amplification, del17p, del1p, 1q21 amplification) drive disease progression and drug resistance. MGUS — present in 3–4% of adults over 50 — is the universally recognized precursor, progressing to myeloma at 1% per year. Risk factors include: Black/African American race (2–3 times higher incidence than whites), advanced age, male sex, obesity, personal or family history of MGUS or MM, immune suppression, and occupational exposure to pesticides, solvents, and radiation. There is no environmental carcinogen with established causality comparable to tobacco in lung cancer; the etiology is predominantly genetic.

Active myeloma is defined by the CRAB criteria plus biomarkers of malignancy (SLiM-CRAB per IMWG 2014). CRAB criteria: Calcium elevation (hypercalcaemia >11 mg/dL) causing nausea, confusion, constipation, and polyuria; Renal insufficiency (creatinine >177 µmol/L or creatinine clearance <40 mL/min) from cast nephropathy, hypercalcaemia, or amyloid; Anaemia (haemoglobin <10 g/dL) causing fatigue, dyspnoea, and pallor; Bone disease — osteolytic lesions, osteoporosis, pathological fractures — causing skeletal pain (back, ribs, hips), hypercalcaemia, and spinal cord compression. Bone pain — particularly axial (spine, ribs, pelvis) — is the most common presenting symptom, present in 70% of patients. Hyperviscosity syndrome from IgM-type MM causes headache, visual blurring, and confusion (rare; more typical of WM). Susceptibility to infections — particularly encapsulated bacteria (Streptococcus pneumoniae, Haemophilus influenzae) due to immunoparesis — presents as recurrent pneumonia and sinusitis. Peripheral neuropathy may be disease-related (VGKCc-antibody neuropathy in POEMS syndrome) or treatment-related (bortezomib, thalidomide).

Myeloma diagnosis requires: ≥10% clonal plasma cells in bone marrow biopsy (or biopsy-proven plasmacytoma) PLUS evidence of CRAB end-organ damage or biomarkers of malignancy (serum free light chain ratio ≥100, bone marrow plasma cells ≥60%, >1 focal lesion on MRI). Investigations: serum and urine protein electrophoresis with immunofixation (identifies M-protein type: IgG most common, then IgA, IgD, light chain only); serum free light chains (Freelite assay); bone marrow aspirate and trephine biopsy with FISH cytogenetics (del17p, t(4;14), t(14;16), 1q21 amplification — high-risk cytogenetics with poor prognosis); skeletal survey (plain X-rays) or whole-body low-dose CT (superior sensitivity) or whole-body MRI or PET-CT for bone disease. LDH, beta-2 microglobulin, and albumin for R-ISS staging. The R-ISS integrates ISS stage (beta-2 microglobulin + albumin), LDH, and high-risk cytogenetics into three prognostic groups: R-ISS I (median OS not reached), II (median OS 83 months), III (median OS 43 months).

Smoldering myeloma with low and intermediate risk per IMWG criteria is observed without treatment; high-risk SMM may be treated with lenalidomide-dexamethasone (DETERMINATION-like approach) or enrolled in clinical trials. Active myeloma requires immediate treatment. Transplant-eligible patients (generally age <70, ECOG PS 0–2, no severe comorbidities): induction therapy with quadruplet Dara-VRd (daratumumab, bortezomib, lenalidomide, dexamethasone) per GRIFFIN/PERSEUS trials, followed by high-dose melphalan + autologous stem-cell transplantation (ASCT), then maintenance lenalidomide ± daratumumab. ASCT improves PFS by approximately 18 months over standard induction. Dara-VRd induction per PERSEUS trial achieved MRD negativity rates of 67% vs 48% with VRd alone. Transplant-ineligible patients: Dara-VRd (MAIA regimen: daratumumab-lenalidomide-dexamethasone) or bortezomib-melphalan-prednisone (VMP). Relapsed/refractory myeloma: isatuximab-pomalidomide-dexamethasone (IKEMA), carfilzomib-daratumumab-dexamethasone, or idecabtagene vicleucel/ciltacabtagene autoleucel (BCMA-directed CAR-T therapy, FDA-approved for ≥4 prior lines). Zoledronic acid (monthly × 2 years) is standard for bone disease prevention.

Multiple myeloma prognosis has improved dramatically with modern triplet and quadruplet therapy. Median overall survival for all patients is now 6–8 years with current treatment, up from 3–4 years in the early 2000s. Transplant-eligible patients achieving MRD negativity with Dara-VRd induction and ASCT have 5-year progression-free survival rates of 80–85% in the PERSEUS trial. R-ISS stratification provides key prognostic information: R-ISS Stage I (low-risk cytogenetics, low LDH, ISS I) has median OS not yet reached in modern series; R-ISS Stage III (high-risk cytogenetics including del17p or t(4;14), elevated LDH, ISS III) has median OS of approximately 43 months. High-risk cytogenetics — del17p, t(4;14), t(14;16), 1q21 gain — are the most powerful adverse prognostic factors for response durability and overall survival. MRD negativity (assessed by next-generation flow or sequencing at 10⁻⁵ depth) is the strongest predictor of long-term outcomes; MRD-negative patients have dramatically better progression-free and overall survival across all clinical risk groups. A subset of young patients achieving sustained MRD negativity may have outcomes approaching functional cure. Relapsed disease is managed with multiple sequential lines of therapy — isatuximab combinations, CAR-T cell therapy (cilta-cel achieving median PFS >2 years in CARTITUDE-1), and bispecific antibodies (teclistamab) — progressively extending survival. Long-term monitoring includes M-protein quantification, serum free light chain ratio, and MRD assessment at key disease milestones.

There are no established strategies to prevent myeloma from developing de novo. MGUS surveillance — designed to detect progression to active myeloma at the earliest treatable stage — is the key preventive framework. Risk stratification by Mayo Clinic MGUS model uses three factors: M-protein >15g/L, non-IgG subtype, and abnormal serum free light chain ratio; low-risk MGUS (0 factors) has 1% 10-year progression risk; high-risk MGUS (3 factors) has 58% 10-year risk. Low-risk MGUS: repeat serum protein electrophoresis in 6 months; if stable, annual monitoring thereafter. High-risk MGUS: annual monitoring with M-protein, FLC, CBC, and renal function. Bone marrow biopsy is not needed for low-risk MGUS without changes. Obesity management may reduce myeloma risk modestly. Patients with MGUS and SMM should be counselled about symptoms of CRAB criteria and encouraged to report promptly.

Urgent hematology referral is required for: new bone pain with a lytic lesion on imaging, unexplained hypercalcaemia, unexplained renal impairment with proteinuria, normocytic anaemia with elevated total protein or abnormal protein electrophoresis band, or recurrent severe infections suggesting immunoparesis. Any patient with unexplained back pain and a high ESR, elevated total protein, or Bence-Jones proteinuria on urine dipstick (often missed as it is not detected by standard dipstick) should have myeloma excluded with serum protein electrophoresis and FLC. Cord compression from a vertebral plasmacytoma or pathological fracture is an oncological emergency: back pain with bilateral leg weakness, urinary retention, or sensory level requires emergency MRI spine and neurosurgical/radiation oncology consultation. Patients with known MGUS should not ignore new-onset back pain or fatigue — these may signal myeloma progression requiring re-evaluation.