40
Treatment
Table 5. Musculoskeletal Toxicities
G2: Moderate weakness with
or without pain limiting
age-appropriate instrumental
ADL.
• Hold ICPi temporarily and may resume upon
symptom control, if CK is normal and prednisone
dose <10 mg ; if worsens, treat as per G3.
• NSAIDs as needed.
• Referral to rheumatologist or neurologist.
• If CK is elevated (× 3 ULN or more), initiate
prednisone or equivalent at 0.5–1 mg/kg/day.
• May require permanent discontinuation of ICPi
in cases with G2 symptoms if patient had other
objective findings of severe muscle involvement such
as very elevated enzymes, or extensive involvement
as determined by EMG, MRI or histology). ICPi
should not be restarted until CK is normal and
clinical manifestations of myositis are resolved.
G3–4: Severe weakness with
or without pain; limiting self-
care ADL
• Hold ICPi.
• Consider hospitalization for patients with severe
weakness severely limiting mobility, respiratory,
dysphagia, or rhabdomyolysis.
• Urgent referral to rheumatologist and/or
neurologist.
• Initiate prednisone 1 mg/kg/day or equivalent.
• For patients with severe compromise, start 1–2 mg/
kg of methylprednisolone IV or higher dose bolus.
• Consider plasmapheresis in patients with acute/
severe disease as guided by rheumatolog y/
neurolog y.
• Consider IVIG therapy, noting onset of action is
slower.
Note: Plasmapheresis immediately after IVIG will
remove immunoglobulin.
• Consider other immunosuppressant therapy
including biologics (e.g., rituximab), TNFα or
IL-6 antagonists if symptoms worsen or if no
improvement after 2 weeks. Other synthetic
immunosuppressants such as methotrexate,
azathioprine, or mycophenolate mofetil could be
considered for maintenance**, or if symptoms and
CK levels do not resolve entirely after 4 weeks.
Rituximab is used in primary myositis.
• Consider permanent discontinuation of ICPi.
** Strongly urge maintenance with synthetic
immunosuppressants be undertaken in collaboration with
rheumatolog y or neurolog y.
(cont'd)
