Leukemia is the mostcommon type of cancer kids get,but it is still very rare.Leukemia involves the
blood andblood-forming organs,such as the bone marrow.________(46)
A kid with leukemiaproduces lots of abnormal white blood cells in the bone marrow. Usually,white
blood cells fightinfection,but the white blood cells in a person with leukemia don't work theway they're
supposedto.________(47)The abnormal white blood cells multiply out of control,fillingthe bone marrow
and making it hardfor enough normal,infection-fighting white blood cells to form.Other bloodcells一such as
red blood cells(thatcarry oxygen in the blood to the body's tissues)and platelets(that allow bloodto
clot）一are also crowded out by the whiteblood cells of leukemia. These cancer cells may also move to other
parts of thebody,including the bloodstream,where they continue to multiply and build up.
Although leukemiacan make kids sick,most of the time it is treatable,and kids get better. Almostall
leukemia patientsare treated with chemotherapy,which means using anti-cancer drug.
________(48)Chemotherapyquickly goes to work,traveling through the blood to the bone marrow.
There,the drugs canattack the cancer cells.After several weeks of chemotherapy,many kids begin tofeel
better.
Some children withleukemia will also have to have radiation therapy,too.________(49)If the cancer
isn't getting betterfrom using the usual amounts of chemotherapy and radiation,then a kid withleukemia
will probably needmore treatment一with higherdoses of chemotherapy and radiation to finally kill the cancer
cells.But thisheavy-duty treatment will also harm the normal cells in the kid's bone marrowtoo,and the
bone marrow will nolonger be able to produce normal blood cells.So,doctors will then give a kid一or anyone
else with bonemarrow that is no longer working一normal bone marrow tissue from someone else who is
healthy.________(50)
___________（48）
A.The chemotherapydrugs are given through a catheter,a narrow tube that is inserted into a bloodvessel, sometimes in the kid's upper chest.
B.Early symptoms ofleukemia are often overlooked,since they may resemble symptoms of the flu orother common diseases.
C.This is a specialprocedure called a bone marrow transplant,and it helps the patient make newblood cells so they can recover from the leukemia.
D.Bone marrow is theinnermost part of some bones where blood cells are first made.
E.They don't protectthe person from infections very well.