Breast cancer is a common malignancy that affects many individuals worldwide. Triple-negative breast cancer (TNBC) represents a distinct and aggressive subtype, accounting for approximately 10% to 20% of all breast cancer diagnoses.
Understanding Triple Negative Breast Cancer
The term “triple negative” refers to the absence of three specific proteins on cancer cells: estrogen receptors (ER), progesterone receptors (PR), and human epidermal growth factor receptor 2 (HER2). These receptors are typically present in other breast cancer subtypes and can be targeted with hormone therapy or HER2-targeted drugs. The absence of these receptors means TNBC does not respond to such treatments.
The absence of these receptors contributes to TNBC’s aggressive nature, as it tends to grow and spread more quickly than other breast cancer types. TNBC is also more likely to spread beyond the breast, leading to metastatic disease, and has a higher chance of returning after initial treatment. Research indicates that TNBC is more prevalent in younger women (under 50) and individuals of African descent. About 70% of breast cancers associated with a BRCA1 gene mutation are triple-negative.
Diagnosis and Staging
The diagnostic process for breast cancer begins with imaging tests like mammography, ultrasound, or MRI. After a suspicious area is identified, a biopsy obtains tissue samples for laboratory analysis. A common method is a core needle biopsy, which removes small tissue cylinders.
Pathology testing of these biopsy samples identifies TNBC. Cancer cells are checked for estrogen receptors, progesterone receptors, and HER2 protein. If all three tests are negative, triple-negative breast cancer is confirmed.
Staging then determines the extent of the cancer’s spread within the body. This involves evaluating the tumor’s size, whether it has spread to nearby lymph nodes, and if it has metastasized to distant organs. Staging helps guide treatment decisions and predict the disease’s course. Breast cancers are typically staged on a numerical scale from 0 to 4, with lower numbers indicating smaller, more localized tumors.
Treatment Approaches
Chemotherapy is a primary treatment modality for TNBC due to the absence of hormone receptors and HER2 overexpression, which limits other targeted therapy options. Chemotherapy agents, such as anthracyclines and taxanes, are often used to target and destroy cancer cells. These drugs can be given before surgery, known as neoadjuvant chemotherapy, to shrink larger tumors and potentially make them easier to remove.
Surgery, either a lumpectomy (removing only the tumor and a small margin of surrounding tissue) or a mastectomy (removing the entire breast), is a common treatment for localized TNBC. Radiation therapy may follow surgery, especially if the tumor was large or if cancer cells were found in the lymph nodes, to reduce the risk of recurrence.
Newer targeted therapies and immunotherapies are emerging for TNBC, offering additional options. For instance, PARP inhibitors like olaparib (Lynparza) and talazoparib (Talzenna) are approved for TNBC patients with BRCA gene mutations, as these drugs target DNA repair pathways in cancer cells. Immunotherapy drugs, such as pembrolizumab (Keytruda), a checkpoint inhibitor, are used for advanced TNBC where cancer cells express the PD-L1 protein. These immunotherapies work by boosting the body’s immune response against the cancer.
Prognosis and Follow-Up
The prognosis for TNBC has historically been considered less favorable than other breast cancer subtypes due to its aggressive nature and higher risk of recurrence, particularly within the first five years after diagnosis. However, advancements in treatment, including the integration of chemotherapy, surgery, and radiation, along with newer targeted therapies and immunotherapies, are improving outcomes. The risk of recurrence generally decreases significantly after five years.
Regular follow-up appointments and surveillance are important after TNBC treatment. Patients typically see their oncologist every three to six months for the first three years, then every six to twelve months for years four and five, and annually thereafter. A yearly mammogram is recommended for those who still have breast tissue. It is important to report any new or unusual symptoms to the healthcare team, as these could indicate a recurrence.
Supportive care helps manage potential side effects of treatment, which can include fatigue, pain, and neuropathy. Clinical trials play a significant role in advancing TNBC treatment by investigating new therapies and combinations. Participation in these trials can offer access to cutting-edge treatments and contribute to the understanding and improvement of TNBC care.