Breast cancer is a complex disease with varied characteristics that influence its behavior and treatment. To effectively address this diversity, breast cancers are categorized based on specific biological markers present in the cancer cells. One such classification, known as “triple positive,” indicates the presence of three particular markers that help guide treatment strategies. This designation signifies that the cancer cells exhibit features responsive to certain targeted therapies.
Understanding the Positive Markers
Estrogen Receptor (ER) Positivity
Estrogen receptors are proteins found inside or on the surface of cells, including some breast cancer cells. When estrogen, a hormone naturally produced in the body, binds to these receptors, it can act like a key in a lock, stimulating the cancer cells to grow and divide. Breast cancers that have these estrogen receptors are termed ER-positive (ER+). This positivity is significant because it means the cancer’s growth is fueled by estrogen, making it potentially responsive to treatments that block estrogen’s effects.
Progesterone Receptor (PR) Positivity
Similar to estrogen receptors, progesterone receptors are proteins that can bind to progesterone, another hormone. When progesterone connects with these receptors on cancer cells, it can also promote cell growth. Cancers possessing progesterone receptors are classified as PR-positive (PR+). The presence of PR often indicates that the estrogen receptor pathway is functional and that the tumor may be more responsive to hormone therapy.
Human Epidermal Growth Factor Receptor 2 (HER2) Positivity
HER2 (Human Epidermal Growth Factor Receptor 2) is a protein located on the surface of all breast cells that helps control cell growth and division. In some breast cancers, there are too many copies of the HER2 gene, leading to an excessive amount of HER2 protein on the cancer cell surface, a condition known as HER2 overexpression. This overexpression causes cancer cells to multiply rapidly and can make the cancer more aggressive. HER2-positive status means the cancer is driven by this protein and can be targeted by specific anti-HER2 therapies.
Identifying Triple Positive Breast Cancer
Determining if breast cancer is triple positive involves a series of laboratory tests performed on a tissue sample from the tumor. The initial step in this diagnostic process is typically a biopsy, where a small piece of the suspicious tissue is removed for examination. This tissue sample is then sent to a pathology lab for detailed analysis.
One primary method used is immunohistochemistry (IHC), which detects the presence and levels of ER, PR, and HER2 proteins within the cancer cells. For ER and PR, the results are often reported as a percentage of cells that stain positive, indicating the presence of these receptors. For HER2, IHC provides a score ranging from 0 to 3+, where a score of 3+ indicates HER2 positivity.
If the IHC result for HER2 is equivocal (a score of 2+), further testing is conducted to confirm HER2 status. This often involves a fluorescence in situ hybridization (FISH) test or a chromogenic in situ hybridization (CISH) test. These tests analyze the cancer cells’ DNA to count the number of HER2 gene copies. A higher than normal number of HER2 gene copies confirms HER2 positivity. If the biopsy results indicate that the cancer cells are positive for estrogen receptors, progesterone receptors, and HER2 protein overexpression, the breast cancer is then classified as “triple positive.”
Treatment Approaches
Treatment for triple positive breast cancer is a comprehensive approach, leveraging the three markers to effectively target the cancer. This involves a combination of therapies tailored to the individual patient, considering cancer stage, menopausal status, and overall health.
Hormone therapy is a primary treatment for ER and PR-positive breast cancers. These medications block estrogen and progesterone from attaching to cancer cell receptors or reduce the body’s hormone production. Examples include tamoxifen, which blocks estrogen receptors, and aromatase inhibitors, which lower estrogen levels in postmenopausal women. This approach starves cancer cells of the hormones needed for growth.
For the HER2-positive component, targeted therapies block the HER2 protein or deliver chemotherapy directly to HER2-positive cells. Monoclonal antibodies like trastuzumab and pertuzumab are used; they attach to the HER2 protein on the cancer cell surface, inhibiting growth signals. Antibody-drug conjugates, such as ado-trastuzumab emtansine (T-DM1), combine a HER2-targeted antibody with a chemotherapy drug, delivering it directly to cancer cells. These HER2-targeted therapies are given with chemotherapy, sometimes before surgery (neoadjuvant therapy) to shrink the tumor, or after surgery (adjuvant therapy) to eliminate remaining cancer cells.
Chemotherapy is a standard part of the treatment plan, especially for HER2-positive cancers, as it destroys rapidly dividing cancer cells throughout the body. It can be administered alongside targeted therapies. Beyond systemic treatments, local therapies like surgery (lumpectomy or mastectomy) remove the primary tumor. Radiation therapy may also be used after surgery to target any remaining cancer cells in the breast area and reduce local recurrence risk.
Prognosis and Ongoing Care
The prognosis for triple positive breast cancer has significantly improved due to targeted therapies. While HER2 overexpression historically indicated a more aggressive cancer, these markers now provide actionable targets for effective treatments. Patients who respond well to treatment can achieve favorable five-year survival rates. The availability of therapies targeting estrogen, progesterone, and HER2 pathways offers a more favorable outlook compared to breast cancers without these targets, such as triple-negative breast cancer. Response to treatment is a significant factor influencing overall prognosis.
Ongoing monitoring and follow-up care are important after initial treatment. This involves regular appointments with the healthcare team, occurring every few months initially and then annually after five years. Annual mammograms are recommended for the treated breast (after lumpectomy) or the remaining breast (after mastectomy). Continued hormone therapy may be prescribed for several years to help prevent recurrence. A personalized follow-up approach, considering individual factors and treatment response, helps ensure long-term well-being.