Herceptin and HER2 positive breast cancer
Not all breast cancers are the same. There are many types and characteristics of breast cancer. Some breast cancer is HER2 positive (the rest are called HER2 negative).
HER2 positive breast cancer is a breast cancer that tests positive for a protein called human epidermal growth factor receptor 2 (HER2), which promotes the growth of cancer cells. In about 20 per cent of breast cancers, the cancer cells make an excess of HER2 due to a gene mutation. This gene mutation and the elevated levels of HER2 that it causes can occur in many types of cancer, not just breast cancer.
HER2+ breast cancer is different
HER2+ breast cancer cells have more HER2 than normal breast cells:
- Having too many HER2 receptors may make the cancer cells grow and divide faster, creating more HER2+ cancer cells
- HER2+ breast cancer is considered aggressive because it grows and spreads quickly. HER2+ breast cancers tend to be more aggressive than other types of breast cancer. They’re also less responsive to hormone treatment.
However, treatments that specifically target HER2 are very effective.
Herceptin (chemical name Trastuzumab)
Herceptin is a drug therapy that targets HER2+ breast cancer (both early stage and advanced (metastatic) stage breast cancer).
Herceptin specifically targets HER2, kills these cancer cells and decreases the risk of recurrence.
Effectiveness statistics: usually Herceptin doubles the effectiveness of other cancer treatments e.g. if chemotherapy adds 2% benefit, Herceptin adds another 2% benefit (adding a total of 4% to survival rates over ten years).
How Herceptin is administered
Herceptin is given by IV infusion every 21 days for 12 months. It is usually given along with traditional chemotherapy but it may also be used alone or in combination with hormone-blocking medications, such as an aromatase inhibitor or tamoxifen.
Side effects of Herceptin
Herceptin is usually well tolerated, but it does have some potential side effects, such as congestive heart failure and allergic reaction.
Herceptin can damage the heart and its ability to pump blood effectively. This risk has ranged between 5% to 30%. The damage can be mild and result in either no symptoms or signs of mild heart failure, like shortness of breath. Women who experience mild or more serious heart damage can stop taking Herceptin and start taking heart-strengthening medications. This often brings heart function back to normal.
Other infusion reactions consist of:
- Fever and chills
- Nausea and vomiting
- Pain and muscle aches
- Shortness of breath
- Very low blood pressure
- Lack of energy and strength
Herceptin causes flu like symptoms in about 40% of the people who take it. Side effects generally become less severe after the first treatment.
Heart scans are required each 12 weeks
Before starting Herceptin therapy, an echocardiogram or a MUGA (multigated blood-pool imaging) scan is required as a baseline for heart functioning. In NZ, each 12 weeks, a heart scan is repeated to monitor any changes.
A MUGA scan takes about an hour. In this test, a tiny amount of radioactive material is injected into a vein in your arm. This material temporarily hooks onto your red blood cells. You lie still while a special camera that can detect the radioactive material takes pictures of the blood flow through your heart as it beats.
Funding and effectiveness
In New Zealand, Herceptin is publicly funded for treating early stage breast cancer as either a nine week or 12 month treatment course. Herceptin for advanced breast cancer is publicly funded for 12 months, but the treatment can be extended under certain criteria.
There has been controversy over Herceptin’s cost and effectiveness. At this point, studies show that 12 months of Herceptin is the most effective protocol with an approximate cost of $6000 per treatment.
- Breastcancer.org http://www.breastcancer.org/treatment/targeted_therapies/herceptin/
- The Herceptin website http://www.herceptin.com/breast/herceptin/
- The New Zealand Ministry of Health websitehttp://www.moh.govt.nz/moh.nsf/indexmh/cancercontrol-treatment-herceptin
- The Mayo Clinic.com http://www.mayoclinic.com/health/breast-cancer/AN00495