Last Updated: 2011-06-03 14:46:04 -0400 (Reuters Health)
By Deena Beasley
CHICAGO (Reuters) - Tailoring cancer drugs to target the molecular signature of an individual patient's tumor helps more than a scattershot approach, according to early-stage research.
The strategy is not an option for every type of cancer, but medical advances have led to the development of a number of drugs that target specific gene mutations in tumors, such as Roche's Herceptin for a certain type of breast cancer or Gleevec, sold by Novartis.
A phase 1 study conducted at the University of Texas MD Anderson Cancer Center found that matching therapies -- most still experimental -- to genetic markers led to higher rates of tumor shrinkage and survival in patients with advanced cancer.
The results were presented on Friday in Chicago at the annual meeting of the American Society of Clinical Oncology.
"The concept is quite simple ... we think you should match the abnormality with the targeted drug," said Dr. Razelle Kurzrock, professor and chair of MD Anderson's Department of Investigational Cancer Therapeutics.
The study involved 852 patients with cancer that was inoperable or had spread beyond the primary site. It found that 27 percent of the 175 patients with a single gene aberration who were treated with a matched drug had tumor shrinkage.
That compared to a response rate of 5 percent in the 438 patients without an aberration receiving the targeted drugs.
Patients who were treated with drugs that did not match their genetic mutations -- had a response rate of 8 percent.
Median survival was 15.8 months for patients with one mutation who were treated with a matched drug, compared with 9.7 months for those patients who were not matched to a targeted therapy.
Dr. Kurzrock said use of molecular testing for cancer patients is not yet standard clinical practice, although it is becoming more common as new drugs are approved and testing is made available.
Since the signing of the National Cancer Act 40 years ago, the average five-year survival rate for all U.S. cancer patients has risen by 18 percent, according to ASCO.
That has been due largely to earlier detection and to improvements in traditional chemotherapy drugs -- which work by interfering with cell replication throughout the body, causing harsh side effects like nausea, hair loss and fatigue.
Newer targeted drugs, made possible by the decoding of the human genome, aim to block specific pathways that cancer cells in particular need to grow and reproduce. The list of targets is an alphabet soup of gene and protein names, such as PIK3CA, mTOR, MEK, EGFR, RET and BRAF.
Elaine Silk, 54, was diagnosed nine years ago with melanoma, a deadly form of skin cancer.
She has endured numerous surgeries and drug regimens -- including a round of immune boosters that required hospitalization and caused her brain to swell -- but considers herself cancer-free after a year of treatment with an experimental BRAF-blocking drug.
"There are a few side effects, but nothing like before ... my hair is really curly," said Silk, who lives in rural Texas. "I take three pills twice a day ... I look at it like medication for high blood pressure that keeps the disease under control."
Dr. Kurzrock said more work is needed since the MD Anderson study was an analysis of retrospective data, rather than a randomized trial.
She also said it would make sense to match targeted therapies to patients with earlier-stage cancer.
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