MadSci Network: Medicine

Re: Cancercells in blood. Why can't cancer be caught from blood transfusions.

Date: Fri Sep 26 11:46:44 2003
Posted By: Sarah Earley, Graduate student
Area of science: Medicine
ID: 1063519449.Me

Hi Joan,

Theoretically cancer could be "caught" from a blood transfusion if the 
blood donor had metastatic cancer (cancer that spreads from the 
initial tumor site).  The chances of this occurring are low, though.  
Less than 1 in 1000 cancer cells in the blood are estimated to survive 
when cancer metastasizes in a person, so the probability of the 
cancer cells escaping detection by the immune system of an entirely 
different person are even less than 1 in 1000.  

I found the following information on the American Cancer Society 

Cancer Survivors: Blood Donation
The risk of getting cancer from a transfusion is extremely small. Even 
if cancer cells were present in donated blood, the immune system of 
the person receiving the blood would destroy the cells. A possible 
exception would be in transfusion recipients with weakened immune 
systems, which might not be able to fend off the cancer cells. 
Because of this possibility, in certain cases cancer survivors are not 
allowed to donate blood for other people. 
People who were treated for cancer with chemotherapy or hormonal 
therapy (such as tamoxifen) cannot donate blood. Nor can anyone 
with leukemia or lymphoma. Cancer survivors who were treated with 
surgery or radiation therapy may donate blood if they have been 
cancer-free for at least five years. Potential donors who have had only 
superficial skin cancers that were removed or destroyed (and 
therefore have little risk of cancerous cells entering the bloodstream) 
may not have to wait that long. Ultimately, it's up to the doctor in 
charge of the donor center whether or not a person is allowed to 
donate. This is especially true if a potential donor's medical records 
are not available for review. 

I hope this helps!

Sarah Earley
Rensselaer Polytechnic Institute

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