Weapon in the War on Cancer
Supplies of the new breast cancer drug, Herceptin, began arriving at clinics and doctors’ offices this month, ushering in a new era of cancer treatment that attempts to target the very flawed genetic mechanisms that cause the disease.
Herceptin is undoubtedly a major advance. But it has limits.
The drug is for women with breast cancer that has spread to other parts of their bodies, or metastasized, a condition that typically yields very low survival rates. And Herceptin works only in women whose tumors overproduce a protein called HER2 / neu. (The gene is also referred to as erbB-2 and ERBB2.)
“In one-third of breast cancers, that gene has been amplified,” says Anna Wu, an associate research scientist at the Beckman Research Institute in Duarte. “The cell is more sensitive and responsive to the signaling process that controls growth.”
In these women, breast cancer tends to be more aggressive, and patients have higher recurrence and mortality rates.
Herceptin is a genetically engineered antibody that is designed to attack specific cancer cells--in this case, the cells that produce HER2 / neu. It works by keeping the protein from reproducing and thus helps shrink the tumor.
But Herceptin, which is made by Genentech, a South San Francisco biotechnology firm, is no cure. Studies show that in 45% of cases women improved while taking Herceptin and chemotherapy compared with a 29% improved rate in women taking chemotherapy alone. Women taking Herceptin on average experienced 7.2 months before the disease progressed, contrasted with 4.5 months for women on standard chemotherapy.
Herceptin is not without risks. Studies show it can weaken the heart muscle and lead to congestive heart failure in some patients. Patients on the medication are advised to undergo regular heart function monitoring.
Most patients eventually relapse. Overall, Herceptin improved by 16% the odds of surviving a full year. Most patients gained about three extra months of life because of the drug--precious time, to be sure.
Herceptin merits enthusiasm foremost for what it represents, says Dr. Dennis Slamon, director of the Revlon / UCLA Women’s Cancer Research Program at UCLA’s School of Medicine and a key player in Herceptin’s development.
“Herceptin proved the concept that if we show what is broken in the cell we can improve therapies,” he says.
This sounds like such good news that, according to Slamon, some women are upset to discover that they do not have the genetic flaw that the medicine targets. And the enthusiasm surrounding the medication has led to some confusion about exactly whom it benefits.
“Women with breast cancer first need to have a test to see if HER2 / neu is there,” Slamon says. “Seventy percent of tumors do not contain the alteration. Remember, if you do not test negative, that is not a bad thing.”
Most physicians agree, however, that women who are diagnosed with metastatic breast cancer should have the HER2 / neu test. One test called the HercepTest was approved by the FDA recently to test specifically for HER2 / neu overproduction. However, there are other tests available. Which test a woman takes may depend on which laboratory does the testing.
Joan Breitman of Laguna Beach insisted on having a HER2 / neu test even before her doctor was convinced it was helpful. She was first diagnosed with breast cancer in 1995. The cancer returned in 1996 and, hearing about the clinical trials with Herceptin, she asked her doctor for the test.
The test showed that Breitman’s tumor did overproduce the HER2 / neu protein. When the disease spread to her bone marrow and liver earlier this year, she applied to enter the Genentech studies. So many women wanted to participate in the Herceptin trials that a lottery system was established to determine who would receive it. Breitman’s name was drawn the day after she entered.
“That brought home for me how important Herceptin is for women who need it right now,” she says. Two friends with breast cancer also entered the lottery but were not selected to receive the drug. Both died this past summer.
Now that the drug is approved, most candidates for the therapy will have that chance, although there is still some concern about who will pay for it. The medication is expensive, and so far most major health plans have not confirmed that they will cover it.
Genentech is charging $575 per dose for the drug. But final costs to the patient--or insurers--could range from $930 to $2,500 per dose, according to some sources.
Genentech has a program to provide Herceptin free to women without health insurance and who cannot afford the drug.
