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Researchers Determine Clinical Outcomes For MDS Patients With A Rare Abnormality In Chromosome 20

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Friday, August 26, 2011

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European researchers recently found that clinical outcomes for myelodysplastic syndromes patients with a rare abnormality in chromosome 20, called isoderivative chromosome 20, were comparable to those of patients with a deletion in chromosome 20.

They also discovered cellular features that can be used to identify patients with isoderivative chromosome 20.

“This study will improve the identification of MDS patients with [isoderivative chromosome 20] and will allow a better estimation of the prevalence of this under-diagnosed entity,” said the study’s lead author, Dr. Francois Mullier of the University of Namur in Belgium.

The researchers recommended the targeted use of a technique called fluorescence in situ hybridization (FISH) to identify patients suspected to have isoderivative chromosome 20 because conventional chromosomal profiles sometimes do not identify patients with this rare abnormality.

Chromosomes, which are usually X-shaped, contain the genetic information of a cell. Although healthy individuals have 23 pairs of chromosomes, patients with myelodysplastic syndromes (MDS) frequently have abnormalities in their chromosomes. In these cases, chromosomal segments or arms may be missing, added, duplicated, or interchanged.

In some patients with MDS or acute myeloid leukemia (AML), the long arm, “q,” of chromosome 20 is missing, abbreviated as del(20q). According to the study’s authors, this deletion occurs in approximately 3 percent of MDS and AML patients. Prior research has demonstrated that MDS patients with a deletion of the long arm of chromosome 20 survive longer than patients without the deletion (see related Beacon news).

A less common abnormality, called isoderivative chromosome 20, occurs when an extra copy of the long arm replaces the short arm of one of the copies of chromosome 20. Additionally, in this mutation segments from the interior of the chromosome have been deleted.

According to the study authors, this abnormality occurs in approximately 0.5 percent of MDS and AML patients. However, they suspect that this may underestimate the true occurrence of isoderivative chromosome 20 because it is often not detected in routine tests.

Unlike a deletion in chromosome 20, the prognostic value of isoderivative chromosome 20 has not yet been determined due to lack of reliable data and low patient numbers.

In the current study, the European researchers aimed to identify the impact of this rare abnormality on MDS clinical outcomes.

The researchers retrospectively analyzed data from 34 MDS patients with either a deletion in chromosome 20 or isoderivative chromosome 20. The median patient ages were 68 and 67 years, respectively.

The FISH technique identified two patients with isoderivative chromosome 20 who were missed with routine detection.

The researchers found that there were no significant differences in outcome among the two patient groups.

“In our study, the overall survival and progression-free survival did not statistically differ in MDS patients with a deletion in chromosome 20 and isoderivative chromosome 20 groups,” said Dr. Mullier.

For patients with isoderivative chromosome 20, the median overall survival and progression-free survival were 68 and 65 months, respectively. These values were not yet reached for patients with a deletion in chromosome 20.

The frequency of autoimmune disorders was comparable for both patient groups. Nearly 10 percent of patients with a deletion in chromosome 20 developed an autoimmune disorder, compared to 8 percent of patients with isoderivative chromosome 20.

For more information, please refer to the article in Annals of Hematology (abstract).


Author: By Jessica Langholtz
Source: The MDS Beacon
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