COLUMBUS, Ohio - An international group of cancer specialists has developed a new classification for cancers of the blood that in some cases will change when treatment will begin and what treatment will be received.
The physicians have worked five years to develop the new classification system, which will be used by the World Health Organization.
"The changes aren't just cosmetic -- they will improve how some cancers are treated," said Clara Bloomfield, director of Ohio State University's Comprehensive Cancer Center. For example, the number of abnormal cells that must be present in the diagnosis of acute myeloid leukemia (AML) versus myelodysplastic syndrome has changed. Formerly, the diagnosis of AML required that 30 percent of abnormal, or blast, cells be present. Now, the diagnosis is made when 20 percent of cells are abnormal.
"This is a significant difference," said Bloomfield. "Earlier, a patient with 20 to 30 percent blasts was not said to have leukemia." Instead, they were categorized as having 'refractory anemia with excess blasts in transformation,' and as a result, they received minimal treatment.
"That has now been eliminated," said Bloomfield. "Many of us felt that these patients really had leukemia, but that we had found it at an earlier stage of the disease. Now someone with 20 percent blasts will be treated with high-dose chemotherapy for acute leukemia."
The new WHO classification was published in recent issues of the Journal of Clinical Oncology and of the Annals of Oncology. Bloomfield was co-chair for the more than 40 hematologists and oncologists involved in the project, and she co-authored the paper. More than 50 pathologists were also involved in the work.
The new system, which will be phased in over the coming years, consolidates knowledge about these diseases that scientists have gained over the past decade. "This is the first classification system for these malignancies that has been agreed to around the world," said Bloomfield. "It reflects a different way of thinking about these malignancies. In practical terms, it will mean quicker and more effective treatment for many patients."
In the past, the classification of leukemias and lymphomas was based largely on the appearance of the malignant cells under the microscope. Little additional information was available about the biology and course of the diseases. As a result, "many patients were lumped together who didn't belong together because we thought they had a similar disease," said Bloomfield.
"The new classification is the first to, in a serious way, go beyond what we see under the microscope to classify cases." For example, for the first time, it incorporates cytogenetics -- the study of chromosomal abnormalities -- in identification of subsets of leukemia.
It also takes into account such things as the response of the cells to certain antibodies, the clinical course of the disease, and response of the disease to treatment.
As a result, the names of some leukemias and lymphomas are being phased out in favor of names that demonstrate the cell that gave rise to the malignancy. Previously, lymphomas were divided into two groups, either Hodgkin's lymphoma or nonHodgkin's lymphoma. The physicians dropped the term 'nonHodgkin's lymphoma' entirely and instead have divided this group into "B-cell neoplasms" and "T-cell neoplasms," along with "Hodgkin's lymphoma." These overall groups are then divided into a number of subgroups.
During the coming decade, Bloomfield expects the diagnosis and treatment of these malignancies to be further refined as more is learned about their differences at the molecular level.
Contact: Clara Bloomfield, (614) 293-7518
Bloomfield-1@medctr.osu.edu
Written by Darrell E. Ward, (614) 292-8456;
Ward.25@osu.edu