What is the typical treatment plan for an adult patient with a diagnosis of multiple myeloma, considering their overall health and medical history?

Multiple Myeloma: Diagnosis and Treatment Overview

Diagnostic Criteria

Multiple myeloma requires ≥10% clonal bone marrow plasma cells or biopsy-proven plasmacytoma plus at least one myeloma-defining event (MDE). 1

The myeloma-defining events include:

• CRAB criteria: Hypercalcemia (serum calcium >11.0 mg/dL), Renal insufficiency (creatinine >2.0 mg/dL), Anemia (hemoglobin <10 g/dL or 2 g/dL below normal), and Bone lesions (lytic lesions, severe osteopenia, or pathologic fractures) 2
• Bone marrow clonal plasmacytosis ≥60% 1
• Serum involved/uninvolved free light chain ratio ≥100 (provided involved FLC ≥100 mg/L and urine monoclonal protein ≥200 mg/24 hours) 1
• >1 focal lesion on MRI 1

Essential Diagnostic Workup

• Serum protein electrophoresis (SPEP) with immunofixation to detect monoclonal protein 2
• 24-hour urine protein electrophoresis (UPEP) - random samples are insufficient 3
• Quantification of IgG, IgA, and IgM immunoglobulins 2
• Complete blood count, serum creatinine, calcium, LDH, and β2-microglobulin 2
• Bone marrow aspiration and biopsy to quantify plasma cell infiltration 2
• Cytogenetic analysis by FISH to detect high-risk features including t(4;14), del(17p), t(14;16), t(14;20), gain 1q, del 1p, or p53 mutation 1
• Whole-body imaging with CT, PET-CT, or MRI to assess bone disease and extramedullary involvement 4, 2

Risk Stratification

High-risk multiple myeloma is defined by the presence of del(17p), t(4;14), t(14;16), t(14;20), gain 1q, del 1p, or p53 mutation. 1

• Double-hit myeloma: Any two high-risk factors 1
• Triple-hit myeloma: Three or more high-risk factors 1
• Revised International Staging System (R-ISS) combines β2-microglobulin, albumin, LDH, and high-risk cytogenetics to predict survival 5

Treatment Algorithm for Newly Diagnosed Multiple Myeloma

Transplant-Eligible Patients

For transplant-eligible patients, induction therapy consists of anti-CD38 monoclonal antibody (daratumumab) plus bortezomib, lenalidomide, and dexamethasone (Dara-VRd) for 3-4 cycles, followed by autologous stem cell transplantation (ASCT). 1

• Standard-risk patients can receive VRd (without daratumumab) as an alternative 6
• Selected standard-risk patients may collect stem cells, receive additional induction cycles, and delay transplant until first relapse 6
• High-dose melphalan 200 mg/m² is the preferred preparative regimen prior to ASCT 7
• Peripheral blood progenitor cells are the preferred stem cell source 7

Post-Transplant Maintenance

• Standard-risk patients: Lenalidomide maintenance 6, 1
• High-risk patients: Bortezomib plus lenalidomide maintenance 6, 1

Transplant-Ineligible Patients

For transplant-ineligible patients, treatment consists of VRd for 8-12 cycles followed by maintenance, or alternatively daratumumab, lenalidomide, and dexamethasone (DRd) until progression. 6, 1

Alternative regimens for transplant-ineligible patients include:

• Bortezomib/melphalan/prednisone (VMP): Bortezomib 1.3 mg/m² subcutaneously days 1,8,15,22; melphalan 9 mg/m² orally days 1-4; prednisone 60 mg/m² orally days 1-4; repeated every 35 days 8
• Lenalidomide/low-dose dexamethasone (Rd): Lenalidomide 25 mg orally days 1-21; dexamethasone 40 mg orally days 1,8,15,22; repeated every 28 days 8
• Daratumumab is FDA-approved in combination with lenalidomide and dexamethasone for newly diagnosed patients ineligible for ASCT 9

Smoldering (Asymptomatic) Myeloma

Patients with smoldering myeloma should not receive immediate treatment. 7, 2

• Observation with monitoring at 3-6 month intervals with laboratory tests 2
• Annual bone survey or as clinically indicated 3
• Multiparameter flow cytometry may predict progression risk (>95% abnormal plasma cells indicates higher risk) 3

Treatment of Relapsed/Refractory Disease

At first relapse, triplet therapy is preferred over doublet therapy, with regimens containing two novel agents (proteasome inhibitor, immunomodulatory drug, or monoclonal antibody) plus steroids. 2

FDA-Approved Regimens for Relapsed/Refractory Disease

• Carfilzomib/lenalidomide/dexamethasone (KRd): Carfilzomib 20 mg/m² (cycle 1) and 27 mg/m² (subsequent cycles) IV days 1,2,8,9,15,16; lenalidomide 25 mg orally days 1-21; dexamethasone 40 mg days 1,8,15,22; 28-day cycles 8
• Carfilzomib once weekly 20/70 mg/m² in combination with dexamethasone (Kd) or daratumumab plus dexamethasone (DKd): Starting dose 20 mg/m² on Cycle 1 Day 1, escalate to 70 mg/m² on Cycle 1 Day 8 if tolerated; administered as 30-minute infusion on days 1,8,15 of each 28-day cycle 10
• Daratumumab combinations: FDA-approved with lenalidomide/dexamethasone, bortezomib/dexamethasone, carfilzomib/dexamethasone, or pomalidomide/dexamethasone for relapsed/refractory disease 9
• Pomalidomide/dexamethasone: Pomalidomide 4 mg orally days 1-21 of each 28-day cycle for patients who received ≥2 prior therapies including lenalidomide and a proteasome inhibitor 11

Triple-Class Refractory Disease

For triple-class refractory patients (refractory to proteasome inhibitor, immunomodulatory drug, and anti-CD38 antibody), selinexor/dexamethasone or belantamab mafodotin monotherapy is recommended. 4

• CAR-T cell therapy and bispecific antibodies are additional options for heavily pretreated patients 1

Special Populations

For patients with t(11;14) who are refractory to lenalidomide and proteasome inhibitor-sensitive, venetoclax plus bortezomib and dexamethasone (VenVd) is recommended. 4

Supportive Care

Bone Disease Management

Long-term bisphosphonates should be administered to reduce skeletal events. 7, 2

Tumor Lysis Syndrome Prophylaxis

For patients with high tumor burden, renal insufficiency, or elevated LDH, aggressive IV hydration with normal saline (150-200 mL/hour to achieve urine output >100 mL/hour) and rasburicase (0.2 mg/kg IV single dose or 3-6 mg fixed dose) is recommended before initiating chemotherapy. 2

• Do not delay chemotherapy for extended periods while attempting conservative measures alone, as this worsens outcomes 2

Thromboprophylaxis

Thromboprophylaxis is mandatory for patients receiving immunomodulatory drugs (lenalidomide, pomalidomide, thalidomide) in combination with other therapies. 10, 11

• The choice of regimen should be based on individual thrombotic risk factors 11

Infection Prophylaxis

Consider antiviral prophylaxis to decrease the risk of herpes zoster reactivation. 10

Premedication Requirements

Dexamethasone premedication (administered 30 minutes to 4 hours before treatment) is required for all doses during Cycle 1 to reduce infusion-related reactions. 10

• Reinstate dexamethasone premedication if infusion reactions occur in subsequent cycles 10

Common Pitfalls and Caveats

• Hydration must be carefully monitored in patients at risk for cardiac failure; adjust based on volume status 10
• Monitor serum potassium levels regularly during carfilzomib treatment 10
• For patients with BSA >2.2 m², calculate drug doses using a BSA of 2.2 m² 10
• Dose adjustments are not needed for weight changes ≤20% 10
• Multiagent chemotherapy has not proven superior and may be inferior in elderly patients 7
• Spinal cord compression requires immediate intervention with high-dose dexamethasone, surgical decompression if due to bone fragments, and local radiotherapy 7
• When monitoring with free light chain assays, use the same test for serial measurements to ensure accurate quantification 7

Follow-Up Monitoring

For patients in remission, follow-up every 3-6 months includes CBC, serum chemistry (creatinine, albumin, calcium, LDH, β2-microglobulin), quantitative immunoglobulins, SPEP with immunofixation, and serum free light chain assay. 3

• Annual bone survey or as clinically indicated 3
• MRI, CT, or PET-CT as clinically indicated for suspected progression or extramedullary disease 3
• Bone marrow assessment when disease progression is suspected 3