Approximately two-thirds of breast cancers are estrogen (ER) and/or progesterone receptor (PgR) positive, meaning the cancers’ growth are fed by one or both hormones. Knowing if a tumor is ER/PgR-positive is important because these breast cancers are the ones likely to respond to hormone (or endocrine) therapies, like tamoxifen and the aromatase inhibitors, which have greatly reduced breast cancer recurrences and deaths over the past several years.
But methods for testing ER/PgR vary from one lab to another, and up to 20 percent of ER and PgR test results may be inaccurate, an issue that Susan G. Komen for the Cure® raised in its 2006 white paper, “Why Current Breast Pathology Practices Must Be Evaluated.” To address the problem, the College of American Pathologists (CAP) and the American Society of Clinical Oncology (ASCO) issued a joint guideline intended to improve the accuracy of testing for the presence of ER/PgR in breast cancer.
The new CAP-ASCO guideline, released April 20, is an important step toward reducing false test results. The expert panel that developed the guideline set out several recommendations related to tissue-handling processes and testing procedures as well as how the test results are reported. Estrogen receptor levels are typically reported as a percent of total cells positive for the receptor, but different labs use different cut points for classifying a tumor as ER-positive. The panel recommended the cut point be set at one percent. In other words, if one percent or more of the cells are positive, the tumor should be classified as ER/PgR-positive. Evidence shows even “weakly” positive tumors (one percent to 10 percent) will respond to hormone therapy, and the panel recommended hormone therapy be considered for these cases.
The guideline also recommends ER/PgR testing for almost all breast cancer patients. Anyone with newly diagnosed invasive breast cancer should receive ER/PgR testing. Additionally, doctors should always test patients with a breast cancer recurrence. The CAP-ASCO panel also sees value in testing ductal carcinoma in situ (DCIS) but stopped short of formally recommending the tests for DCIS. Women with DCIS should discuss the pros and cons of ER/PgR testing with their doctors.
CAP and ASCO previously collaborated in the development of a testing guideline for HER2, which is a receptor found in approximately 20 percent of breast cancers. Like ER, HER2 is a receptor that can be targeted with specific drugs that improve breast cancer outcomes. Both organizations are promoting the guidelines and providing tools to speed their adoption. Additionally, CAP is offering a breast cancer certification program for pathologists, which Komen intends to support with a grant.
Breast cancer is the most common cancer diagnosed in women and is the leading cause of cancer-related deaths for women worldwide. Because so many breast cancer patients stand to benefit from endocrine therapy, which is widely available, we must also ensure access to accurate testing to identify those patients. Susan G. Komen for the Cure applauds CAP and ASCO for developing this important guideline as it will ultimately result in more lives saved.
Komen encourages patients to ask if their pathology lab follows the CAP-ASCO guidelines for HER2 and ER/PgR testing. To learn more about breast cancer diagnosis including factors that affect treatment decisions, visit www.komen.org. Visit ASCO’s sites (www.asco.org or www.cancer.net) or CAP’s sites (www.cap.org or www.mybiopsy.org) for more information about the guidelines.