The myelodysplastic syndromes (MDS) represent a spectrum of clonal stem cell malignancies that are characterized by dysplastic and ineffective hematopoiesis. They are associated with progressive cytopenias and a variable risk of bone marrow failure and leukemic transformation.[1,2] The exact cause of MDS is not clearly understood. MDS is thought to originate as a result of complex interactions between malignant progenitor cells (malignant clone), the bone marrow stroma, and the microenvironment.[3] In general, as the disease progresses, bone marrow function declines. Identification of key molecular, immunological, and hematological elements of the pathobiology of myelodysplastic syndromes has provided insight into potential therapeutic targets. Understanding the novel mechanisms of anti-tumor activity has promoted robust scientific discovery in terms of active therapies for this disease.
The first classification system for MDS was developed in 1976. A risk-stratification system, the International Prognostic Scoring System (IPSS), was developed in 1997, providing information critical for treatment selection.[4] The first agent for active treatment of MDS was approved by the US Food and Drug Administration (FDA) in May 2004. Since then, two additional active agents have been approved for MDS, and several other agents are in clinical trials.
The first clinical guidelines for treatment were released in July 2004 by the National Comprehensive Cancer Network. Several revisions have been made since their development, reflecting the rapidly changing treatment guidelines. Improvement in supportive care strategies, including hematopoietic growth factors, blood component support, iron-chelation therapies, and antibiotics, has in turn improved overall survival of patients with the disease. The disease is most common in elderly patients, thus presenting additional challenges for therapeutic management. The challenge for oncology nursing professionals is to integrate knowledge of selective therapies based on disease characteristics, risk stratification, and individual patient attributes.
CLINICAL PRESENTATION, DIAGNOSTIC EVALUATION, AND RISK STRATIFICATION
Symptoms associated with one or more cytopenias—such as fatigue, fever, recurrent or prolonged infections, bruising, or bleeding—are the most common symptoms that prompt the patient to seek medical care. The initial patient evaluation most often includes a complete blood count, which reveals normocytic or macrocytic anemia, normal to decreased neutrophils, and variable platelet counts. Anemia is observed in 90% of patients with MDS, either at initial presentation or during the course of their disease. A careful history and additional laboratory analysis should be pursued to exclude other causes of cytopenias. (See Table 1.)
If MDS is suspected, a bone marrow biopsy and aspirate with cytogenetic analysis will be necessary to exclude other diseases associated with bone marrow failure and allow full classification and risk stratification of MDS. These procedures will yield a tissue diagnosis, information on morphology, cell counts, blasts percentage, bone marrow cellularity, any atypical findings, and cytogenetic evaluation data. This information is critical to identification of favorable or unfavorable subtypes and specific options for therapy.
Diagnostic classification
Diagnostic classification of MDS is based on the three primary classification systems: The French American British (FAB) classification system, the World Health Organization (WHO) system, and the International Prognostic Scoring System (IPSS). Collectively they provide guidelines for assignment of disease nomenclature and risk stratification based on hematopathology and cytogenetic criteria. (See Table 2.) Risk stratification is based on three criteria—percentage of blasts, number of cytopenias, and favorable or unfavorable cytogenetics.
Low-risk disease (low – Intermediate 1) is associated with longer survival and less common transformation to acute leukemia. Treatment goals for the lower-risk patients are aimed at improving hematopoiesis and reducing the risk of cytopenias. High-risk disease (Intermediate 2 – High) is associated with rapid leukemic transformation and poor prognosis. Treatment is aimed at control of the aggressive component of the disease and improved survival. Consideration of diagnostic findings that may favor selection of specific therapies is critical to initiating the therapy with the greatest potential benefit early in the course of disease.
THERAPEUTIC GOALS AND TREATMENT SELECTION
There are challenges in trying to determine optimal treatment strategies for people with MDS. Until recently, many treatment strategies were based on anecdotes, abstracts and consultation meetings, and relatively few published clinical trials. Recent clinical trial results are encouraging but generalized treatment recommendations are limited by the different eligibility and response criteria used in the earlier trials. Continued refinement of response evaluation criteria such as the International Working Group (IWG) Criteria and consensus treatment guidelines such as NCCN criteria will provide a framework for comparison of clinical trial results in the future.
The primary goals of therapy are to improve quality of life, minimize treatment toxicity, decrease transfusions, decrease infections, and prolong survival. Selection of the most effective therapy should be based on the unique characteristics of the individual patient, including specific MDS subtype, risk category, performance status, physiological age, comorbid conditions, and lifestyle. Familiarity with recent advances in treatment options is essential to selecting the best therapy for the individual patient.
For low- to intermediate-risk MDS patients (those in the IPSS Low and Int-1 prognostic risk groups), blood counts may remain stable over several months or longer, therefore a short period of observation is recommended to determine a patient's degree of clinical stability. Monitoring every 2 to 4 months is recommended for patients in stable condition. Patients who develop progressive cytopenias or transfusion dependence are then considered for active treatment. Patients with high-risk disease require more aggressive and immediate intervention. (See Table 3.)
Supportive care has been the mainstay of MDS treatment for the last 20 years. Until recently, no active therapies were available. Supportive care continues to be important in treatment of symptoms associated with the disease or toxicities of newly developed active therapies. Supportive care includes observation, quality of life assessment, growth factors, antibiotics, iron-chelation therapies, and transfusion support. However, it is important to recognize that supportive care measures do not change the underlying disease and may also be associated with toxicity, cost, and frequent clinical evaluation or visits.
