Radiotherapy and Intrathecal Therapy Considerations in CNS Multiple Myeloma

Radiotherapy Parameters

• For symptomatic central nervous system lesions in multiple myeloma, the recommended whole‑brain or focal radiotherapy dose is 3000 cGy delivered in 10–15 fractions. This regimen is based on expert consensus from hematology societies and is intended to achieve local disease control while limiting toxicity. 1

Intrathecal Therapy Limitations

• Systemic anti‑myeloma agents do not attain therapeutic concentrations in the cerebrospinal fluid, therefore intrathecal chemotherapy (e.g., methotrexate, cytarabine, corticosteroids) is required for leptomeningeal disease to ensure adequate drug exposure within the CSF compartment. This limitation is highlighted in recent leukemia literature. 2

Differentiating Peripheral Neuropathy from CNS Involvement

• Sensory neuropathy caused by proteasome inhibitors (such as bortezomib) or immunomodulatory drugs (such as thalidomide) manifests as a length‑dependent, stocking‑glove distribution and does not represent central nervous system involvement. Clinicians should distinguish this peripheral toxicity from true CNS myeloma manifestations when evaluating neurological symptoms. 3