Luminal A breast cancer

Luminal A breast cancer is HR positive/HER2 negative (HR+/HER2-), meaning:

• It expresses estrogen or progesterone (or both) hormone receptors (HR).
• It doesn’t express human epidermal growth factor receptor 2 (HER2) proteins.

What are the main subtypes of breast cancer?

Breast cancer has four main subtypes. Doctors define breast cancer by whether it’s either estrogen or progesterone HR or HER2 proteins. These factors tell doctors how aggressive the cancer may be, and how it may respond to various treatments:

• HR+ indicates at least one HR is present, telling them to grow.
• HR- indicates no HR are present.
• HER2+ indicates the HER2 protein is present, affecting how quickly they grow.
• HER2- indicates the HER2 protein isn’t present.

Doctors test the cancer cells to determine their subtype. The four main breast cancer subtypes are:

• Luminal A (HR+/HER2-), as described above
• Luminal B (HR+/HER2+), which expresses at least one HR, expressed HER2 and has high levels of the Ki-67 protein
• Basal-like or triple-negative (HR-/HER2-), which doesn’t express either HR or HER2
• HER2-enriched (HR-/HER2+), which doesn’t express either HR but does express HER2

What is luminal A breast cancer?

Luminal A (HR+/HER2-) is the most common subtype of breast cancer, accounting for about 68 percent of cases, according to the National Cancer Institute’s SEER database (SEER). Compared to the other subtypes, luminal A:

• Grows slower
• Is less aggressive
• Typically has improved outcomes

Luminal A breast cancer symptoms

Symptoms of luminal A breast cancer are like those of other breast cancers. They include:

• A lump or mass in the breast
• Swelling in part of the breast (or in the whole breast), under the arm or near the collarbone
• Breast or nipple pain
• Inversion of the nipple or unusual discharge
• Thickened, red, dry, flaking or dimpling of the breast skin

Luminal A breast cancer diagnosis

The process used to diagnose any breast cancer is similar. When a patient has symptoms or a suspicious mammogram, the doctor will perform a physical exam and other imaging tests before conducting a breast biopsy to remove a sampling of the mass for testing in the lab. From that sample, the doctor can determine whether the mass is cancer, and if it is, identify the cancer’s subtype.

An immunohistochemistry lab test is the most common way to determine the breast cancer’s subtype. This test uses special dyes to highlight the presence of estrogen or progesterone HR (or both) and HER2 proteins.

Newer genetic tests, known as gene expression profiling, may also determine the cancer’s subtype along with other key details, such as:

• Its HR and HER2 expression, indicating the cancer subtype
• The evidence-based treatment options for that type
• The sequence in which treatments should be administered
• Whether the cancer has the potential to come back (recur) after initial treatment

The most common gene expression tests for HER2- breast cancers are:

• The Oncotype Dx^® test, which analyzes 21 genes to get a “recurrence score” from 0 and 100
• Prosigna^®, which may predict the risk of recurrence in the next 10 years by looking for 50 genes and classifying the results as low, intermediate or high risk
• MammaPrint^®, which analyzes 70 genes to determine the cancer’s risk of recurrence
• Breast Cancer Index™ test, which looks for 11 genes to predict recurrence and responsiveness to hormone therapy

Luminal A breast cancer treatment

Treatment options for luminal A breast cancer depend on how advanced the cancer is when it’s first detected. Treatments include surgery, radiation therapy and sometimes chemotherapy. Because luminal A breast cancer is HR-positive, it’s often responsive to hormone therapy. Generally speaking, when the cancer is diagnosed in its early stages, the patient is more likely to undergo less-invasive treatments.

Luminal A breast cancer prognosis

After a luminal A breast cancer diagnosis, most people want to learn more about its prognosis. Luminal A breast cancer has a five-year survival rate of 94.4 percent, while luminal B’s rate is 90.7 percent, HER2-enriched is 84.8 percent and triple-negative is 77.1 percent, according to SEER.

Luminal A vs. luminal B

Luminal B is much less common than luminal A, making up only 10 percent of breast cancer cases, according to the SEER. The biggest difference between the two is that luminol B expresses the HER2 protein, which may quicken the growth of cancer cells. As a result, luminal B breast cancer is typically more aggressive and receives a higher grade and a poorer prognosis than luminal A.

The following chart shows the different characteristics between luminal A and luminal B breast cancers.

Survival rates, according to the SEER:

• Five-year:
  • Luminal A: 94.4%, 5-year
  • Luminal B: 90.7%, 5-year
• Localized (only in the breast tissue):
  • Luminal A: 100%, local
  • Luminal B: 98.8%, local
• Regional (spread to nearby lymph nodes):
  • Luminal A: 90.1%, regional
  • Luminal B: 89.3%, regional
• Distant (spread further from the breast):
  • Luminal A: 31.9%, distant
  • Luminal B: 46.0%, distant