Freelance Writing Jobs | Today's Articles | Sign In

Predictive Biomarkers

Offering Cancer Patients Personalized Therapeutic Options

Dec 4, 2008 Amy Erickson

There are several well-documented biomarkers and genetic tests on the market today that help oncologists determine the best course of therapy for cancer patients.

Predictive biomarkers are playing a significant role in personalized cancer therapy. Researchers now have the technology to analyze a tumor’s genetic signature to identify biomarkers that can help direct treatment.

Although novel biomarkers are discovered every day, not all biomarkers lead to validated diagnostic tests. However, there are several well-researched cancer biomarkers that oncologists use to offer patients the best possible treatment.

CYP2D6 Gene

Among women with advanced breast cancer, roughly 35 percent of those with estrogen receptor–positive tumors do not respond to tamoxifen therapy and tumors that do respond may eventually become resistant to tamoxifen treatment. CYP2D6 is a gene involved with tamoxifen metabolism. Studies show that tamoxifen does not work as well in post-menopausal women with breast cancer who carry a variant of CYP2D6. An estimated 7 percent to 10 percent of women with breast cancer may have this variant, which affects how tamoxifen is broken down into active by-products including endoxifen. A study published in the December 2005 issue of The Journal of Clinical Oncology found that women who inherit the variant of CYP2D6 appear to be at a higher risk for relapse.

Epidermal Growth Factor Receptor (EGFR)

Over-expression of the biomarker EGFR in tumors causes prolific cell growth. EGFR inhibitors are seen as an important new class of anti-cancer agents. There are several targeted drugs already on the market that inhibit EGFR, including tarceva (erlotinib) and iressa (gefitinib) for non-small cell lung cancer, and cetuximab (erbitux) for head, neck and colorectal cancer.

ERCC1

A study published in the September 7, 2006 issue of the New England Journal of Medicine found that the lack of expression of ERCC1, a DNA-repair protein found in patients with non-small cell lung cancer, could predict the benefit of adjuvant cisplatin therapy. Cisplatin is a platinum-based chemotherapy drug. Conversely patients with ERCC1-positive tumors may have to endure the side effects of therapy with little therapeutic benefit. The next step is to develop a diagnostic test using ERCC1 as a biomarker.

Estrogen Receptor (ER)

ER is over expressed in about 70 percent of breast cancer cases, according to breastcancer.org. ER-positive cancers are more likely to respond to anti-estrogen therapies such as tamoxifen and aromatase inhibitors arimidex (anastrozole), aromasin (exemestane), and femara (letrozole). Estrogen and ER have also been implicated in the development or progression of ovarian, colon, prostate and endometrial cancer. However, more research needs to be done to validate ER as a biomarker for these cancer types.

Human Epidermal Growth Factor Receptor 2 (HER-2)

HER-2 is a validated biomarker in breast cancer. The drug herceptin (trastuzumab) targets the HER-2 receptor, which is over expressed in about 25 percent of breast cancers. Women who are found to be positive for over expression are candidates for herceptin therapy in the metastatic and adjuvant settings.

UGT1A1

A gene called UGT1A1 has been found to play a role in the metabolism of a colon cancer drug called camptosar (irinotecan), according to a study published in the May 2006 issue of the Journal of Clinical Oncology. Variations in UGT1A1, a gene that produces the enzyme UDP-glucuronosyltransferase, can influence a patient’s ability to break down camptosar, leading to possible increased blood levels of the drug and a higher risk of side effects. The Invader UGT1A1 Molecular Assay provides oncologists with information about the most effective dosage of camptosar for individual patients.

The copyright of the article Predictive Biomarkers in General Medicine is owned by Amy Erickson. Permission to republish Predictive Biomarkers in print or online must be granted by the author in writing.