What is HER2 positive breast cancer ?
The excessive presence of HER2 (human epidermal growth factor) protein receptors in breast tissue lead to malignant growth and clinically termed as HER2 positive breast cancer. In general, breast tissues contain HER2 (human epidermal growth factor) protein receptors at the cell surface, but unwanted HER2 receptors excite cell division and lead to cancerous growth. The breast cancer test report when indicates the elevated level of levels of the HER2 protein that medically termed as HER2 positive breast cancer1.
There are four diagnostic tests are available to detect the HER2 positive breast cancer2,3.
IHC test (ImmunoHistoChemistry)
The presence of excessive amount of HER2 protein in breast cancer cells can be detected through the ImmunoHistoChemistry test. The test report can be obtained as negative (0), even 1+ also indicates negative. Borderline can be described as 2+ and a positive result can be identified as 3+ that mean over-expression of HER2 protein.
FISH test (Fluorescence In Situ Hybridization)
The presence of several copies of the HER2 gene in the breast cancer cells can be identified through the Fluorescence In Situ Hybridization test. The test report of the FISH test can help to determine the HER2 gene amplification (positive) or no HER2 gene amplification (negative).
SPoT-Light HER2 CISH test (Subtraction Probe Technology Chromogenic In Situ Hybridization)
This test is also similar as FISH test in regards to detection of several copies of the HER2 gene in the breast cancer cells. The test report of the SPoT-Light HER2 CISH test can help to determine the HER2 gene amplification (positive) or no HER2 gene amplification (negative).
Inform HER2 Dual ISH test (Inform Dual In Situ Hybridization)
This test is also conducted for identifying the presence of excessive copies of the HER2 gene in the breast cancer cells. The test report of the Inform HER2 Dual ISH test can help to determine the HER2 gene amplification (positive) or no HER2 gene amplification (negative).
All the above-mentioned tests are conducted for the purpose of identifying the HER2 gene amplification or HER2 protein over-expression which is indicated by HER2-positive in the pathology report. The finding of this assists in determining HER2-positive Breast cancer. The aggressive nature of the HER2-positive breast cancers have a faster growth tendency and also spread faster and tend to relapse, which are not similar in HER2-negative breast cancers.
Different research results showed that the test report is not always correct to determine the status of HER2 protein due to the variation of the laboratory markers to classify positive and negative HER2 status. The pathologist who study the test report also follows different criteria to fix on whether the results are positive or negative. Most of the time confusion is created when the test report showed borderline and that cannot provide strong HER2-positive or HER2-negative. This lacuna needs to keep in mind during treating a patient with breast cancer, as Inaccurate HER2 test results may cause ineffective treatment prognosis. Therefore, repetition of test or alternative test must be performed to get an accurate result.
The treatment plan varies depending upon the patient condition, clinician’s choice and patient’s response to the provided treatment. The specific criteria, which clinicians considered before determining the treatment plan are:
- Stage of cancer and that depends upon the size and spreading nature of the cancerous growth
- Grade of cancer or speed of malignant growth
- Nature of cancer means HER2 positive or negative
- Presence of hormone estrogen receptor, as presence of this cause responsiveness of hormonal therapy
The following treatment options are available for treating HER2 positive breast cancers2,3,5.
Surgical intervention is not same for every case, depending on the size and location of the cancer doctor will decide which surgery is best for the patient. Even chemotherapy or drug like trastuzumab is also used as a neo-adjuvant treatment for shrinking the size of a large tumor.
Breast-conserving surgery (wide local excision)
In this surgical process along with breast cancer cells, some surrounding breast tissues are also removed. The removal of surrounding tissue is very less, but it can cause scar mark or small dent in the breast. Along with this surgical method, doctor mat prescribes radiation therapy for a better outcome.
Mastectomy (removing the breast)
Sometimes whole breast removal is the only option if the cancer growth is locally widespread or tumor size is very large or radiation therapy is not suitable for the patient.
Surgery to lymph nodes
Sometimes a few or all the lymph nodes present in armpit need to remove out because lymph nodes get affected with cancerous growth or for detecting the stage of cancer.
Chemotherapy is cytotoxic drugs which act against cancerous cells. Chemotherapy usually prescribed for protecting relapsing and termed as adjuvant chemotherapy. Chemotherapy can be prescribed in combination with trastuzumab.
Taxanes and anthracylines are most common chemotherapeutic agents for HER2 positive breast cancer. These two drugs combination with other chemotherapeutic agents like cyclophosphamide, fluorouracil, capecitabine, and methotrexate are prescribed as neo-adjuvant or adjuvant therapy.
The functionality of the targeted therapies is to block the HER2 receptor and thus restrict the excessive cancerous cells growth. The most common commonly used drug in this category is trastuzumab (Herceptin ®) and provide effective result in most of the cases. Other included targeted therapies are Lapatinib (Tyverb ®), Pertuzumab (Perjeta ®) and Trastuzumab emtansine (Kadcyla ®).
High-energy rays are provided through radiation therapy to destroy the malignant cell growth. Usually, radiation therapy is recommended after surgical intervention to reduce the risk of relapsing of cancerous growth. It also reduces the chance of the spreading of cancerous growth to the brain, bone or other distant organs. Radiotherapy can reduce pain and other symptoms.
Oestrogen hormone and related receptors have a role in many types of breast cancer development. The involvement of estrogen receptor in the development of breast cancer is termed as estrogen receptor positive breast cancers (ER-positive breast cancers). The principal of giving hormonal therapy is to reduce the estrogen level in the body and also blocks the estrogen receptor activity. The outcome of this hormonal therapy is to control the cancer growth and relapsing and also reduce the spreading of cancer. Some examples of hormonal therapy are exemestane, anastrozole, letrozole, and tamoxifen.
The incidence rate of breast cancer due to abnormal gene mutation, which leads to excessive HER2 protein is about 1 of every 5 breast cancers or 15–25% breast cancer cases are identified as HER2 positive breast cancer. The disease is specifically detected in women, but very less frequently observed in men. The nature of the HER2 positive breast cancer is more aggressive than other types of breast cancers. But treatments that specially target HER2 are very effective and provide good treatment prognosis, though hormone therapy does not provide effective treatment of HER2 positive breast cancer 1,2,4.
According to the study result conducted by MD Anderson Cancer Center, almost 93.7 % HER2-negative cancer patient can survive five years after detecting cancer . In the case of HER2-positive patients, almost 77.1% can survive 5 years after detection and much higher risk of recurrence than of HER2-negative patients4.
- HER2 positive breast cancer; Macmillan. Cancer Support; Online available at http://www.macmillan.org.uk/cancerinformation/cancertypes/breast/aboutbreastcancer/typesandrelatedconditions/her2%20positive.aspx
- HER2 Status;Breastcancer.org; Online available at http://www.breastcancer.org/symptoms/diagnosis/her2
- Timothy J. Moynihan, HER2-positive breast cancer: What is it?; http://www.mayoclinic.org/breast-cancer/expert-answers/faq-20058066
- Robin Madell; HER2-Positive Breast Cancer Survival Rates and Other Statistics; Online available at http://www.healthline.com/health/breast-cancer/her2-positive-survival-rates-statistics#Occurrence3
- Breast Cancer; American Cancer Society; Online available at http://www.cancer.org/cancer/breastcancer/detailedguide/breast-cancer-treating-targeted-therapy
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