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Leukemia treatment tied to brain tumor risk



Friday July 2 1:17 PM ET 

Leukemia treatment tied to brain tumor risk

NEW YORK, Jul 02 (Reuters Health) -- Children with leukemia who 
have a certain genetic variation are at increased risk of developing a 
brain tumor if they have radiation treatment of the head, according 
to a report.  

US researchers suggest that altering the treatment protocol for 
children carrying this gene defect may reduce their risk of 
developing radiation-associated brain tumors.  

Such brain tumors are a rare side effect of treatment, occurring in 
0.5% to 1.5% of children over a 10- to 20-year period after they 
have been treated with head irradiation for acute lymphoblastic 
leukemia (ALL).  

However, nearly 13% of children (6 out of 52) developed a 
secondary brain tumor 7 to 10 years after treatment at St. Jude 
Children's Research Hospital in Memphis, Tennessee, report Dr. 
Mary V. Relling and colleagues in July 3rd issue of The Lancet.  

``An unusually high frequency of brain tumors seen among children 
enrolled in one of our leukemia treatment protocols... prompted us 
to identify potential causes of this complication,'' the investigators 
write.  

They found that children with a defect in the activity of thiopurine 
methyltransferase, an enzyme that helps break down the drug 
mercaptopurine, were at greater risk of developing a brain tumor. 
Over an 8-year period, those children with the defect had a brain 
tumor incidence of 43% compared with an 8% incidence in those 
without the genetic defect.  

The researchers note that the 52 children in this study received 
more intensive treatment with antimetabolite drugs, powerful anti-
cancer agents, in addition to radiation treatment. The combination 
may have contributed to tumor formation in the children carrying 
the defective gene, according to the report.  

The findings suggest that radiation therapy of the brain should not 
be used to prevent cancer recurrence in children with ALL unless 
the patient is at high risk of having a relapse in the central nervous 
system, Relling and colleagues conclude.  

``Underlying genetic characteristics and treatment variables,'' they 
add, ``may be associated with an increased risk of radiation-
associated brain tumors.''  

At St. Jude Children's Research Hospital, antimetabolite therapy is 
no longer administered with radiotherapy, the team adds.  

SOURCE: The Lancet 1999;354:34-39. 
------------------
Sandy Perle
Technical Director
ICN Dosimetry Division
Costa Mesa, CA 92626
Office: (800) 548-5100 x2306 
Fax:    (714) 668-3149
  
sandyfl@earthlink.net
sperle@icnpharm.com

Personal Website: http://www.geocities.com/CapeCanaveral/1205
        
ICN Dosimetry Website: http://www.dosimetry.com

"The object of opening the mind, as of opening 
the mouth, is to close it again on something solid"
              - G. K. Chesterton -

The opinions expressed are solely, absolutely, positively, definitely those of the author, and NOT my employer

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