The College of American Pathologists (CAP) and the American Society of Clinical Oncology (ASCO) issued a joint guideline today aimed at improving the accuracy of immunohistochemistry (IHC) testing for the expression status of estrogen (ER) and progesterone receptors (PR) in treating breast cancer patients.
Because as many as two-thirds of breast cancers are ER and/or PR-positive, the new guideline has the potential to prolong and save the lives of the vast majority of breast cancer patients worldwide.

To improve the accuracy of ER and PR testing, the CAP and ASCO recommend the following:

• Testing ER and PR status on all newly diagnosed invasive breast cancers (primary site and/or metastatic site), and whenever appropriate, repeat testing in patients with a known breast cancer diagnosis who now present with a local or distant recurrence.
• Establishing uniform testing measures that focus on proven, reliable and reproducible assays and procedures.
• Having testing laboratories validate their assays against existing and clinically validated tests. Results should agree at least 90 percent of the time with those of the clinically validated assays for positive receptor status and at least 95 percent for negative receptor status.
• Transporting breast tissue specimens from the operating room to the pathology laboratory as soon as they are available for gross assessment. The time from tumor removal to initiation of fixation should be kept to one hour or less.
• Performing ER and PR testing in a CAP-accredited laboratory or in a laboratory that meets the accreditation requirements spelled out in the guideline. The CAP will require that every accredited lab performing testing participate in a mandatory proficiency testing program.
• Considering an ER and PR test, performed by IHC, positive if at least one percent of the tumor in the sample tests positive, which helps predict whether a patient is likely to benefit with endocrine treatment. The panel recognized that it is reasonable for oncologists to discuss the pros and cons of endocrine therapy with patients whose tumors contain low levels of ER by IHC (one percent to ten percent weakly positive cells) and to make an informed decision based on available information.

The CAP also developed a list of frequently asked questions to help members and laboratories understand what the new guideline will mean in their practice setting. In addition, a joint press release was posted today on the College's website and on ASCO's website, illustrating the collaboration between the two organizations on behalf of breast cancer patients.

Patients can find a resource guide on the College's patient website, http://www.MyBiopsy.org. In addition, the homepage of MyBiopsy.org features ER/PR breast cancer survivor Ruth Chermok and highlights the life-saving role of pathologists in diagnosing and assisting with the treatment of breast cancer patients.
This is the second time that the two organizations have collaborated on guidelines. In 2007, the CAP and ASCO issued clinical practice guideline recommendations to improve HER2 testing accuracy.