Treatment of Low or Intermediate-1 Risk Primary Myelofibrosis with Bulky Splenomegaly

This protocol addresses first-line management of primary myelofibrosis in patients classified as low risk or intermediate-1 risk who present with disease-related symptoms or bulky splenomegaly — a distinct clinical group where the dominant drivers for treatment are symptom burden and splenic enlargement rather than imminent disease transformation.

Clinical scenario

Treatment approach

First-line therapy centres on an oral JAK inhibitor, with alternative systemic options considered when blood counts are proliferative. The complete selection criteria, decision framework, and sequencing are detailed in the full protocol.

Treatment goals

• At least 10% reduction in spleen volume
• 50% reduction in symptom burden, assessed around 8 weeks after starting therapy

References

Low risk

Intermediate 1

Symptomatic/ bulky spleen

Ruxolitinib is an oral JAK1/JAK2 inhibitor indicated for the treatment of disease-related splenomegaly or symptoms in adult patients with PMF, post-ET MF and post-PV MF.

Often, IFN is considered in low/intermediate-1 group patients with proliferative counts, or in patients with pre-fibrotic MF (pre-PMF).

It can be useful where the primary indication for treatment is control of proliferative blood counts, often in earlier stages of the disease.

Around 80% of patients treated with ruxolitinib experience ≥10% reduction in spleen volume; primary resistance is rare.

Ruxolitinib can elicit rapid symptomatic responses, with nearly 40%–50% of patients achieving a 50% reduction in symptom burden in around 8 weeks when treated with adequate dose density.

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