The Allred Score is a standardized system used in breast cancer pathology to quantify specific proteins within cancer cells. This scoring method provides important information about a tumor’s biological characteristics, guiding treatment decisions.
Understanding the Allred Score
The Allred Score measures estrogen receptors (ER) and progesterone receptors (PR) on breast cancer cells. These receptors are proteins located on the surface or inside cells that can bind to the hormones estrogen and progesterone. When these hormones attach to their corresponding receptors, they can stimulate cancer cells to grow and divide.
The presence and quantity of ER and PR indicate whether a breast cancer is “hormone receptor-positive,” meaning its growth is influenced by these hormones. Approximately 70% of breast cancers are hormone receptor-positive. Classifying the cancer based on these receptors helps determine if hormone-blocking therapies might be effective.
How the Allred Score is Determined
The Allred Score is determined by examining breast cancer tissue samples under a microscope using immunohistochemistry (IHC). This process involves staining the tissue to visualize the hormone receptors. The final score is a sum of two components: the Proportion Score and the Intensity Score.
The Proportion Score assesses the percentage of cancer cells that stain positive for the receptors. This is rated on a scale from 0 to 5. A score of 0 means no positive cells are observed, while a score of 5 indicates that more than 67% of the cells show positive staining.
The Intensity Score evaluates the strength of the staining, reflecting how strongly the receptors are expressed within the positive cells. This score ranges from 0 to 3. A score of 0 signifies no staining, 1 indicates weak staining, 2 represents moderate staining, and 3 denotes strong staining. The final Allred Score is calculated by adding the Proportion Score and the Intensity Score, resulting in a total score that can range from 0 to 8.
Interpreting Your Allred Score
The Allred Score categorizes breast cancer based on hormone receptor status. Scores are categorized as either negative or positive for ER/PR expression. A total Allred Score of 0 or 2 is considered hormone receptor-negative, indicating that cancer cells largely lack estrogen and progesterone receptors.
Scores ranging from 3 to 8 are considered hormone receptor-positive. A higher Allred Score within this range suggests a greater number of receptors and a stronger intensity of their expression. Hormone receptor-positive cancers often rely on estrogen and/or progesterone for their growth and survival, meaning the cancer is sensitive to these hormones.
Allred Score and Treatment Guidance
The Allred Score plays a direct role in guiding breast cancer treatment decisions. For individuals with hormone receptor-positive breast cancer (Allred Score of 3 to 8), hormone therapy is often recommended. This type of therapy, also known as endocrine therapy, targets the hormone receptors on cancer cells or reduces the body’s hormone levels.
Examples of hormone therapies include tamoxifen and aromatase inhibitors. Tamoxifen works by blocking estrogen from binding to its receptors on cancer cells, thereby inhibiting their growth. Aromatase inhibitors prevent the aromatase enzyme from converting other hormones into estrogen, reducing the overall estrogen supply in the body. These treatments aim to starve hormone receptor-positive cancer cells of the hormones they need to proliferate.
In contrast, breast cancers with an Allred Score of 0 or 2, indicating hormone receptor-negative status, do not respond to hormone therapy. These cancers require alternative treatment approaches, such as chemotherapy, targeted therapy, or immunotherapy, as they do not rely on estrogen or progesterone for growth.