HER2 testing is an important predictor of response to therapy in 20%–25% of patients with breast cancer; however, approximately 20% of testing has been reported to be inaccurate. In response, the American Society of Clinical Oncology (ASCO), in conjunction with the College of American Pathologists (CAP), published guidelines for HER2 testing in patients with breast cancer. The expert panel concluded that immunohistochemistry and fluorescence in situ hybridization testing assays are acceptable. They also defined positive HER2 results for either testing methods as well as additional testing methods for final determination of equivocal results. To ensure accurate results, the panel recommended that results be obtained from a CAP-accredited laboratory.

ASCO has also been working on a provisional clinical opinion, an early version of a formal guideline, to assist clinical decision making in colorectal cancer. Approximately 30%–40% of colorectal cancers express a mutated KRAS gene. Although approved for colorectal cancer, cetuximab (Erbitux^®) and panitumumab (Vectibix^®) are ineffective in blocking EGFR in patients with the mutated KRAS gene. As a result, ASCO recommends that patients with colorectal cancer be tested for KRAS mutations prior to the start of treatment with either of these drugs.

• American Society of Clinical Oncology. (2009). ASCO Expert Corner: KRAS testing in people with colorectal cancer. Retrieved from http://www.cancer.net/patient/All+About+Cancer/Cancer.Net+Feature+Articles/Treatments%2C+Tests%2C+and+Procedures/ASCO+Expert+Corner%3A+KRAS+Testing+in+People+With+Colorectal+Cancer
• American Society of Clinical Oncology. (2011). American Society of Clinical Oncology–College of American Pathologists guideline recommendations for human epidermal growth factor receptor 2 testing in breast cancer. Retrieved from http://www.asco.org/ascov2/Practice+&+Guidelines/Guidelines/Clinical+Practice+Guidelines/American+Society+of+Clinical+Oncology-College+of+American+Pathologists+Guideline+Recommendations+for+Human+Epidermal+Growth+Factor+Receptor+2+Testing+in+Breast+Cancer