Targeted Therapy

Targeted therapy is a cancer treatment in which molecules are used to interfere with specific tumor cell proteins in order to stop the characteristic growth and spread of cancer. These proteins are called molecular targets and have been identified for their specific ability to promote growth and survival in a tumor cell. Unlike chemotherapy, targeted cancer therapies act only on the molecular targets while normal cells are unaffected. Targeted therapy depends on the ability to identify molecular targets; one approach is to compare the amounts of individual proteins in cancer cells versus normal cells. Abnormally high levels of proteins usually point to involvement in tumor cell growth. As does the presence of genetically altered proteins that exist only in the cancer cells. So-called fusion proteins, produced by genes from abnormal chromosomes, have also been identified as potential targets.

Once molecular targets have been identified, an agent is developed to interfere with the tumor cell’s ability to grow and survive. Agents are typically small molecules or monoclonal antibodies that interact with targets found on the surface of a cell or inside the cell. Approved targeted cancer therapies include:

  • Hormone therapies—interfere with tumor growth
  • Signal transduction inhibitors—interfere with a cell’s ability to respond to signals
  • Gene expression modulators—alter the proteins responsible for expressing a certain gene
  • Apoptosis inducers—responsible for controlled cell death in cancer cells
  • Angiogenesis inhibitors—stop the growth of a new blood supply to the cancer cells
  • Immunotherapies—signal the immune system to kill cancer cells

Targeted cancer therapies have become an important tool in advancing methods of cancer care, and the modalities described above can even be combined for a more effective treatment program. Targeted therapies have been approved for treating many types of cancers, including:

  • Bladder cancer
  • Brain cancer
  • Breast cancer
  • Cervical cancer
  • Colorectal cancer
  • Head and neck cancer
  • Kidney cancer
  • Leukemia
  • Liver cancer
  • Lung cancer
  • Lymphoma
  • Multiple myeloma
  • Pancreatic cancer
  • Prostate cancer
  • Skin cancer
  • And many more

A limitation for targeted cancer therapies is that the cancer cell can become resistant. Another limitation is the difficulty of developing the precise agent to effectively interfere with the molecular target. While targeted cancer therapies are considered much less toxic than traditional chemotherapy, they are still associated with significant side effects:

  • Diarrhea
  • Liver problems, such as hepatitis, from elevated liver enzymes
  • Skin problems (acneiform rash, dry skin, changes to nails and hair)
  • Problems with blood clotting and wound healing
  • High blood pressure
  • Gastrointestinal perforation (a rare side effect)