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Recent advances in childhood cancer treatments: target therapy

Chemotherapy and radiotherapy have been traditional ways in childhood cancer treatments.  There are many well-known side effects of chemotherapy and radiotherapy such as hair loss and nausea.  However, less well-known side-effects such as organ deficiency and secondary cancer might appear after years of treatment.


The Children’s Cancer Foundation interviewed Dr. Alan Chiang, Clinical Associate Professor of the Department of Paediatrics & Adolescent Medicine of The University of Hong Kong for insights about target therapy.


Dr. Chiang said, target therapy is a prevailing medical term in recent years.  Simply speaking, target therapy means the use of specific drugs to tackle the cancer cells.  Scientists worked on the research of specific drugs based on the characteristics of cancer cells.  This way in drug research helps to increase the survival rate and prevents the normal cells from being affected due to the drug specificity.


Even though ‘target therapy’ is a popular term in recent years, it has been in use in the treatment in early years.  Dr. Chiang illustrated it with a fact.  More than one decade ago, it is found that all trans retinoic acid (ATRA) can work well on the fusion protein PML-RARA, leading to apoptosis in the cancer cells of acute promyelocytic leukemia (APL), the third type of acute myeloid leukemia (AML).


Because this fusion protein PML-RARA is not present in normal blood cells, the drugs are specific to the cancer cells of APL.  Even though the term ‘target therapy’ did not exist at the time, ATRA had then been considered as specific therapy drug for APL.


However, the number of target therapy drugs applied to the paediatric oncology is small.  It is due to the fact that the quantity of drugs research in paediatric oncology is much less than the one in adult oncology.  Also only a few amount of target therapy can pass all tests and be qualified for clinical use.  For instance, Rituximab, a monoclonal antibody against the protein CD20, is used for lymphoma.  3F8 monoclonal antibody therapy is used for neuroblastoma.  Glivec, which can specifically inhibit a certain enzyme, can treat chronic myeloid leukemia (CML).


Take treatment in CML as an example. 


Glivec can specifically target the fusion protein BCR-ABL in CML.  This has changed the whole treatment plan in CML.  The survival rate applied with Glivec is much higher than other standard drugs such as chemotherapy and interferon.  Glivec is well tolerated by most patients and can achieve long term control of CML in 90% of patients.  Thus, Glivec replaces chemotherapy and interferon and becomes the first line drug for CML. 


Then will chemotherapy be totally replaced by target therapy?


Dr. Chiang said that it would not happen in short term.  Actually only Glivec shows the most remarkable clinical effect among target therapy drugs.  Most cancer types cannot be cured with one single drug because the drug resistance will inevitably appear.  Thus, combination of several therapies is applied in clinical treatment.


Dr. Chiang added that 70% of childhood cancer patients can be cured by the standard treatment nowadays.  The advance and application in target therapy is in hopes of increasing survival rate.  He expected that the public will be open-minded to observe the development and application of target therapy drugs and in the same time the public needs to be cautious as scientists who use clinical proof as rationales for drug application.  It should not just seek after new drugs because of fad.


The Children’s Cancer Foundation has been subsidizing child patients in purchasing target therapy drugs.  In the past 5 years, the Foundation subsidized over a million dollars in purchasing target therapy drugs for over 20 child patients.