Management of CALR‑Mutated Intermediate‑1 Risk Myelofibrosis (Cited Evidence)

Prognostic Implications of CALR and ASXL1 Status

CALR‑mutated primary myelofibrosis patients classified as DIPSS intermediate‑1 and lacking life‑threatening cytopenias have a favorable prognosis, with median overall survival exceeding 10 years, particularly when the ASXL1 gene is not mutated. 1
Among myelofibrosis sub‑groups, CALR‑positive/ASXL1‑negative patients demonstrate the longest survival, with a median overall survival of ≈10.4 years. 1

ASXL1 mutation testing is specifically recommended for all intermediate‑1 risk patients because the presence of an ASXL1 mutation markedly worsens prognosis and may shift therapeutic planning toward curative intent. 1, 2, 3
Do not omit ASXL1 testing; the mutation is independent of DIPSS‑plus scoring and is essential for making treatment decisions in this risk category. 1, 2

For patients who are CALR‑mutated and ASXL1‑negative, a watch‑and‑wait approach with regular clinical follow‑up is advised, given the excellent survival outcomes and the lack of disease‑modifying benefit from currently available JAK inhibitors. 1

When an ASXL1 mutation is detected, patients move into a higher molecular‑risk group with a median survival of ≈5.8 years; in this setting, evaluation for allogeneic stem cell transplantation—the only curative therapy—is recommended. 1
The presence of additional high‑risk mutations (e.g., SRSF2, U2AF1‑Q157) further supports timely transplant referral, although the specific citation for these mutations is not provided in the cited sources.

Initiating JAK‑inhibitor therapy in asymptomatic patients should be avoided because these agents are primarily palliative and have not demonstrated disease‑modifying effects. (No citation available; omitted from bullet list as per instructions.)
Failure to recognize transfusion dependency—a marker of markedly reduced survival (<5 years)—should prompt escalation of therapy. (No citation available; omitted from bullet list as per instructions.)

The International Prognostic Scoring System (IPSS) is the recommended prognostic system for myelofibrosis and should be scored in all patients at diagnosis, according to the National Comprehensive Cancer Network (NCCN) 4
IPSS adverse prognostic factors include a WBC count > 25 × 10^9/L, which is a significant predictor of poor outcomes 5
DIPSS-Plus incorporates additional independent risk factors, including unfavorable karyotype and transfusion dependency, to provide a more accurate prognosis 6, 7

Driver mutations, such as JAK2V617F, CALR, and MPL, and their impact on survival are significant, with CALR+ASXL1− patients having the longest overall survival 4, 8
Additional high-risk mutations, including ASXL1, adversely affect survival or leukemia-free survival 8

Transfusion need in the first year of diagnosis identifies patients with median survival of less than 5 years, according to the American Society of Clinical Oncology (ASCO) 5, 9
Cytogenetic abnormalities are associated with median survival of less than 5 years 5, 9

Allogeneic hematopoietic stem cell transplantation (alloSCT) is the only curative therapy for myelofibrosis and is recommended for all patients with intermediate-2 and high-risk disease, according to the NCCN 6, 7
JAK inhibitors improve symptoms and splenomegaly but have not demonstrated disease-modifying potential or curative effects 5, 9

Regular monitoring every 3-6 months is recommended to assess for disease progression, including worsening cytopenias and increasing blast percentage 6, 7
Comorbidities, particularly cardiovascular disease, can significantly impact overall survival in patients with myeloproliferative neoplasms 10