June 6, 2011— -- In September 2009, doctors told Taylor Chance she had melanoma -- a dangerous form of skin cancer that would kill her in six months. But nearly two years later, Chance, a 67-year-old who lives in Rancho Cucamonga, Calif., is still alive thanks to an experimental drug called Vemurafenib, which launches a targeted attack on the cancer's very source.
Vemurafenib, which is being developed by Plexxikon and Roche/Genentech, targets a genetic mutation that causes melanoma in about half of affected patients. In a study presented Sunday at the American Society of Clinical Oncology meeting in Chicago, 84 percent of patients treated with Vemurafenib were alive six months later, compared with 64 percent of patients who received the standard chemotherapy.
"This is a very exciting time for patients," said Dr. Lynn Schucter, chief of hematology oncology at the University of Pennsylvania's Abramson Cancer Center. "You know, this concept of personalized medicine or targeted therapy, this is going to be a revolutionary way to treat patients with cancer."
Cancer occurs when defective genes send abnormal signals to the body's cells, causing them to multiply out of control. But targeted therapies like Vemurafenib can shut down the erroneous signals, stopping cancer cell division in its tracks without affecting healthy, normal cells. That means more effective treatment and fewer side effects.
"Traditional treatments for cancer, such as chemotherapy, are one size fits all," said Dr. Gerald Falchook, assistant professor in the department of investigational cancer therapeutics at MD Anderson Cancer Center in Houston. "We've known about these mutations for a long time, but it's only recently that we have new drugs to target [them]."
Melanoma is the most common form of cancer, affecting approximately 70,000 new people each year. It's also one of the most lethal, each year killing an estimated 9,000 people. But melanoma isn't the only cancer targeted therapy is going after -- it can work on any cancer with genetic roots.
Chance may not really care how Vemurafenib works; she's just happy it does.
"Last year, I thought I would not get to see the birth of my youngest son's first child," she said, "now I'll be here for his first birthday next month ... and I hope for many more."
ABC News' Courtney Hutchison cnotributed to this report.