Type of test Tumor-specimen analysis
Normal findings
Immunochemistry
Negative: < 5% of the cells stain for receptors
Positive: > 5% of the cells stain for receptors
Reverse-transcriptase polymerase chain reaction (RT-PCR)
Negative: < 5.5 units , Positive: > 5.5 units
Test explanation and related physiology
The PR assay is used in determination of the prognosis and treatment of breast cancer and, to a lesser degree, other cancers. This assay helps determine whether a tumor is likely to respond to endocrine medical or surgical therapy. The test is done on breast cancer specimens when a primary or recurrent cancer is identified; it is usually done in conjunction with an estrogen receptor (ER) assay to increase the predictability of a tumor response to hormone therapy. Tumor response rates to medical or surgical hormonal manipulation are potentiated if the ER assay is positive. Tumor response rates are as follows:
• ER positive, PR positive: 75%
• ER negative, PR positive: 60%
• ER positive, PR negative: 35%
• ER negative, PR negative: 25%
Other tumors (e.g., ovarian, melanoma, uterine, pancreatic) are occasionally studied for ER and PR assay. This is done mostly within clinical trials.
Interfering factors
* The use of such hormones as progesterone or estrogen may cause false-negative results.
Procedure and patient care
Before
* Explain the procedure to the patient.
• Prepare the patient for breast biopsy per routine protocol.
• Record the menstrual status of the patient.
• Record any exogenous hormone the patient may have used during the past 2 months.
* Instruct the patient to discontinue exogenous hormones before breast biopsy. This is done in consultation with the physician.
During
• The surgeon obtains tissue.
• This tissue should be placed on ice or in formalin.
• Part of the tissue is used for routine histology. A portion of the paraffin block is sent to a reference laboratory.
• Results are usually available in 1 week.
After
• Provide routine postoperative care.
Abnormal findings
Increased levels
- Hormonally dependent cancer
