Targeted therapies in breast cancer are a type of treatment that specifically targets the molecules involved in the growth and spread of cancer cells. These therapies are designed to interfere with specific molecular pathways that play a crucial role in cancer development. Unlike traditional chemotherapy, which can affect both cancer and normal cells, targeted therapies aim to be more selective and precise, potentially minimizing damage to healthy tissues.

Here are some key points about targeted therapies in breast cancer:

1. **Specific Molecular Targets:** Targeted therapies focus on specific molecules that are involved in the growth and survival of cancer cells. Common targets in breast cancer include HER2 (human epidermal growth factor receptor 2), estrogen receptors (ER), and progesterone receptors (PR).

2. **HER2-Positive Breast Cancer:** HER2 is a protein that promotes the growth of cancer cells. In about 20-25% of breast cancers, there is an overexpression of the HER2 protein. Targeted therapies such as trastuzumab (Herceptin), pertuzumab, and ado-trastuzumab emtansine (T-DM1) are designed to block the effects of HER2 and slow the growth of HER2-positive breast cancers.

3. **Hormone Receptor-Positive Breast Cancer:** Hormone receptor-positive breast cancers rely on hormones, such as estrogen or progesterone, to grow. Targeted therapies like tamoxifen and aromatase inhibitors work by blocking the effects of these hormones or reducing their production, thereby inhibiting the growth of hormone receptor-positive breast cancers.

4. **PARP Inhibitors:** Poly (ADP-ribose) polymerase (PARP) inhibitors, such as olaparib and talazoparib, are targeted therapies used in certain cases of breast cancer, particularly in those with BRCA mutations. These drugs interfere with the ability of cancer cells to repair DNA damage, leading to cell death.

5. **Angiogenesis Inhibitors:** Some targeted therapies aim to disrupt the process of angiogenesis, which is the formation of new blood vessels that supply nutrients to tumors. Bevacizumab is an example of an angiogenesis inhibitor that has been used in combination with chemotherapy for the treatment of breast cancer.

6. **Immunotherapy:** While not strictly a targeted therapy, immunotherapy can also be considered a form of targeted treatment. Immune checkpoint inhibitors, such as pembrolizumab and atezolizumab, are designed to enhance the body's immune response against cancer cells. These drugs have shown promise in certain types of breast cancer.

It's important to note that the effectiveness of targeted therapies can vary depending on the specific characteristics of the cancer and the individual patient. These therapies are often used in combination with other treatments, such as surgery, chemotherapy, and radiation therapy, as part of a comprehensive treatment plan for breast cancer. The choice of therapy depends on factors such as the type and stage of breast cancer, the presence of specific molecular markers, and the patient's overall health. Treatment decisions are typically made in consultation with a multidisciplinary team of healthcare professionals.