Learning that you have cancer cannot be an easyexperience. On top of the fear and anxiety, you wonder how you are going tocope with the chemotherapy and its dreadful side effects. Now, thanks to yearsof research, a new class of drugs with fewer side effects is available in thefight against cancer.
Called targeted therapy, the treatment uses drugs thatare able to specifically identify and attack the cancer cells. “The drugs aredesigned to block specific machinery inside the cancer cell. In that way, wecan zoom in to the errant cells without affecting normal cells or organs. Thismeans greater efficacy of treatment and fewer unwanted effects,” says DrGilberto de Lima Lopes, a Consultant in Medical Oncology and the AssistantDirector for Clinical Research at the Johns Hopkins Singapore InternationalMedical Centre.
“Smart” drugs
According to Dr Gilberto, targeted therapy or “smart”drugs work basically by disrupting cancer growth and spread. They home in oncertain molecules or proteins on cancer cells, which are used for communicationwithin the cells, and therefore, signals that incite cancer cells to grow anddivide incessantly are blocked.
Some “smart” drugs may also work by infusing toxicsubstances into the cancer cells, thereby causing cell death. The drugs alsohelp to stimulate the immune system to defend the body against the attackingcancer cells.
“Once we can identify the specific signaling pathway aparticular cancer relies on heavily, we can design a drug to block thatpathway, and therefore arrest its growth,” explains Dr Gilberto. For example,in breast cancer, the “smart” drug trastuzumab targets the protein HER2/neu, amolecule found on the surface of breast cancer cells. For patients who havethis protein – about 25% of breast cancer patients have it – trastuzumab willexert its effects on the protein while sparing the normal cells.
Benefits of targeted therapy
The current trend among medical oncologists therefore, isto tailor treatment to an individual’s tumour. “We try to characterise eachperson’s tumour as much as possible so as to individualise or personalise thetherapy,” elaborates Dr Gilberto. According to him, the greatest advancementhas been seen in breast cancer, where the most number of targets have beenidentified, and hence their respective “smart” drugs developed.
In addition to having greater efficacy and fewer sideeffects, targeted therapies have also provided treatment options for patientswho may not otherwise be candidates for anti-cancer therapy. For example,elderly patients may have other medical conditions that limit the use ofstandard chemotherapy. “Smart” drugs such as erlotinib and rituximab, which arebetter tolerated and less toxic than conventional chemotherapy, offer thesepatients new hope.
Targeted therapy is currently used in breast, lung andcolon cancers. It is used alone or in combination with conventionalchemotherapy or other targeted therapies.
The future
With different cancers having different types of pathwaydependence, the challenge remains for scientists to identify the weakness of aparticular cancer. Subsequently, researchers will need to design “smart” drugsthat are able to target the weakness as specifically as possible. “With a gooddrug-to-target match, it is possible to have significantly improved survivalrates, greater shrinkage of the tumour or arrested tumour growth,” says DrGilberto.
“Smart” drugs have definitely
given doctors and patients more options as far as cancer treatment isconcerned. With this comes an improvement in overall quality of life,previously not thought possible.
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The drugs are designed to block specific machinery inside the cancer cell. Inthat way, we can zoom in to the errant cells without affecting normal cells ororgans. This means greater efficacy of treatment and fewer unwanted effects,says Dr Gilberto de Lima Lopes, a Consultant in Medical Oncology and theAssistant Director for Clinical Research at the Johns Hopkins SingaporeInternational Medical Centre.
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