Experts present new recommendations on 'overlapping' type of leukemia

Chronic myelomonocytic leukemia (CMML) is a rare disease with overlapping features of two categories of bone marrow and blood cell disorders that poses challenges in clinical management. Joint recommendations on diagnosis and treatment of CMML from two European specialty societies were published today in HemaSphere, the official journal of the European Hematology Association (EHA).

The new document from the EHA and the European LeukemiaNet provides recommendations for standardized diagnosis, prognosis, and appropriate choice of treatment for adult patients with CMML. These recommendations have been established by a panel of European and US experts chaired by Prof. Pierre Fenaux, MD, Ph.D., of Hôpital Saint-Louis, Paris.

Expert Guidance on New Advances to Improve Treatment Outcomes in CMML

Chronic myelomonocytic leukemia is an unusual and highly variable condition representing an "overlap" between two different types of bone marrow and blood cancers: myelodysplastic syndromes (MDS—sometimes called "pre-leukemia") and myeloproliferative neoplasms (MPN—including several types of leukemias).

Occurring in about 1 in 100,000 people each year, mainly older adults, CMML can appear in different ways in different patients. Even for specialists, it can be a difficult condition to manage in terms of making the correct diagnosis, predicting the likely outcome (prognosis), and choosing the best treatment.

Until recently, CMML patients were grouped together with MDS patients. To date, there has been only one randomized trial focusing specifically on treatment for CMML. "Despite an increasing knowledge on the molecular and cellular features of CMML, the clinical management of these overlap MDS/MPN syndromes remains poorly codified," Prof. Fenaux and coauthors write.

To address this knowledge gap, the EHA and European LeukemiaNet assembled a panel of international experts, who were tasked with developing an initial set of clinical practice recommendations for CMML. The new article includes the panel's consensus recommendations, organized into three areas:

• Diagnosis. Blood and bone marrow test recommendations for diagnosis of CMML are presented, including an elevated number of monocytes—a type of white blood cell. Advanced tests including flow cytometry and molecular genetic tests play key roles in narrowing down the diagnosis of CMML.
• Prognosis. Outcome prediction is a critical step, as expected survival varies widely among patients with CMML. Although several predictive models have been developed, the best approach to determining prognosis in individual patients remains unclear. Both patient- and disease-related factors have important implications for predicting outcomes and monitoring the response to treatment.
• Treatment. Several factors affect the choice of treatment for CMML. For some patients with favorable prognostic factors, "watchful waiting" (observation without treatment) may be appropriate. Available treatment options may lead to longer survival, but currently can't cure CMML. Stem cell transplantation remains the only curative therapy for CMML. However, this isn't an option for every patient and survival rates are relatively low. The experts emphasize the need for new transplantation strategies, including approaches to prevent relapse after transplantation.

The new recommendations are an important step forward in developing standardized approaches to clinical management of CMML. However, reflecting the limitations of the available research data, they are based mainly on expert consensus rather than on highest-quality evidence.

The expert panel urges steps to improve the quality of evidence supporting clinical recommendations for CMML. "Inclusion of CMML patients in clinical trials is strongly encouraged at all stages of the disease," the expert panel concludes. They also note that recently established international collaborative networks will help "to clarify the management strategy of CMML in the coming years."