What is Herceptin?Herceptin is the first genetically engineered drug in the fight against breast cancer. The development of this drug started because of a genetic abnormality found in women who have breast cancer. The genetic abnormality is an overexpression of the HER2/Neu protein. These proteins are located on the surface of the cell and interact with the growth factors that cause cell growth and division. Because of the overexpression, the cells divide and multiply faster than normal cells causing the development of cancer. Herceptin is a monoclonal antibody, which binds to the protein causing interference with the growth factors and eventually the death of the cell.
Treatments:Most of the studies determined that a combination of Herceptin and chemotherapy treatments had the most effective results. Overall, patients treated with a combination of Herceptin and chemotherapy had a 50 percent better response rate then patients using chemotherapy alone. The median time to disease progression increased by 65 percent (from 4.6 to 7.6 months). The number of women alive after one year increased from 67 percent to 78 percent. In addition, 28 percent of women did not show evidence of tumor progression at one year compared to 14 percent with chemotherapy alone. The amount of tumor shrinkage was also increased from 32 percent to 49 percent, a 53 percent increase, for patients treated with both Herceptin and chemotherapy. Although, most of these cases did not cure the patient, it did prolong their lives by a significant amount.
The studies done with Herceptin alone had patients that had been previously treated with chemotherapy or had a bone marrow transplant. Although, they did show some improvement the study did not fully reflect how Herceptin would work alone. Therefore, Herceptin appears to work best in combination with other cancer treatments.
Side Effects:When Herceptin was used alone the toxic side effects associated with traditional chemotherapy, such as hair loss, nausea, fatigue, and a drop in blood count were rarely noticed. The side effects associated with Herceptin alone were chills and fevers in about 40 percent of the patients. In treatments that utilized a combination of chemotherapy and Herceptin some toxic side effects were noticed, for example, diarrhea, low white cell count, and infections. The most serious side effect was heart problems in about 15 percent of the patients that were treated with Herceptin and anthracylines, a specific form of chemotherapy. Most of these heart problems were non-fatal and could be controlled with drug therapy.
Importance:Studies have shown that approximately 25 to 30 percent of women with metastatic breast cancer have tumors that overexpress the HER2/Neu protein. According to the American Cancer Society there are approximately 164,000 women with metastatic breast cancer. Consequently, enough women are effected by this genetic abnormality that it is important to develop this drug. Dr. Dennis Slamon, also noted that, "HER2 overexpressing breast cancers are different and need to be treated differently that less aggressive cancer." Therefore, this drug is extremely important for two reasons. One, it is needed to help breast cancer patients and two, it is the first step towards more genetically engineered drugs.
Herceptin is the beginning of a new kind therapy that targets the underlying causes of cancer. One article states, "Unlike the poisons that are currently the main stay of cancer therapy-toxic chemotherapies that kill both cancerous and healthy cells-the new molecular biotherapeutics target and interfere with the tumor cells' genetic root, eventually causing their death. Healthy cells appear to be left untouched." The article explains the major advantage of new cancer treatments over old cancer treatments. This new approach to cancer therapy targets the molecular basis of cancer and eliminates the most painful part of old cancer treatments, the toxic side effects. The long-term impact of Herceptin is still unknown but the outlook is very positive. Researchers are hoping to see many new advances in cancer treatments from the discovery of Herceptin.
references:Genentech, Inc. (produces Herceptin)