Cancer Cell Targeting Therapies
By:
Dr Leong Swan Swan, Senior Consultant
Dept of Medical Oncology, NCC
Cancer has traditionally been treated by surgery, radiotherapy or chemotherapy. Surgery and radiotherapy are localized forms of treatment while chemotherapy exerts its effects systemically. The type of treatment recommended is based on what cancer the patient has and how advanced it is. However, different patients respond differently to treatment given. We now know that, in addition to the type and stage of cancer, there may be other inherent factors causing individual cancers to behave differently. These inherent changes may be excessive or abnormal manifestations of certain proteins or molecules in the cancer cells, stimuli for increased blood supply to the cancer, or genetic alterations leading to failure of autoregulatory mechanism preventing abnormal growth.
Targeted therapy refers to treatment directed specifically at these abnormal manifestations in cancer cells or cancer tissue. Such treatment selectively attack cancer tissue, sparing the normal cells. Hence the associated side-effects tend to be somewhat milder than that expected from chemotherapy. Targeted therapy has been well established for some cancers, like hormonal treatment in prostate cancer and breast cancer. Tamoxifen for example, is particularly effective in receptor-positive breast cancers.
| Some of the other major breakthroughs in targeted treatment include: |
|
Signal transduction inhibitors, which block specific pathways involved in cancer growth. Imatinib (Gleevec) has been shown to be useful for the treatment in gastrointestinal stromal tumours; Erlotinib (Tarceva) and Gefitinib (Iressa) has benefited some patients with lung cancer in whom chemotherapy no longer work. |
|
Monoclonal antibodies eg Trastuzumab (Herceptin) is useful for a subset of breast cancer patients and Rituximab (Mabthera) has been approved for use in Non-Hodgkin’s Lymphoma. More recently, Cetuximab (Erbitux) has been shown to be useful in the treatment of colorectal cancer and head & neck cancer. |
|
Angiogenesis inhibitors inhibit new blood vessel formation, interfering with the growth and spread of the cancer. Bevacizumab (Avastin) has been approved for use in colorectal cancer and it has also been shown to have promising activity in lung cancer. |
|
Gene therapy is largely still experimental. |
The treatment of cancer is still far from satisfactory. The advent of targeted treatment has definitely opened up new horizons in the treatment of a variety of cancers. However, just like chemotherapy, targeted treatment does not always work. There are certain pointers to help identify which patients are more suited to receive such treatment. Continued research will hopefully result in better tailoring of prescribed treatment.
|
