Allred scoring system

Allred scoring system

A clinical instrument based on the percentage of cells that stain by immunohistochemistry for oestrogen receptor (ER) (on a scale of 0 to 5) and the intensity of that staining (on a scale of 0 to 3, for a possible total score of 8). Allred scoring stratifies a breast cancer patient’s ER status into cancers that are likely to respond to hormone therapy with tamoxifen or letrozole. As a rule, breast cancers do not respond to tamoxifen with an Allred score of < 6 or to letrozole with a score of < 3.

Allred scoring
Proportion score
0—No cells are ER +ve.
1—≤ 1% of cells are ER +ve.
2—1–10% of cells are ER +ve.
3—11–33% of cells are ER +ve.
4—34–66% of cells are ER +ve.
5—67–100% of cells are ER +ve.

Intensity score
0—Negative.
1—Weak.
2—Intermediate.
3—Strong.

Allred score
0–1—No effect.
2–3—Small (20%) chance of benefit.
4–6—Moderate (50%) chance of benefit.
7–8—Good (75%) chance of benefit.