Ovarian cancer is usually detected at an advanced stage and, as such, is one of the deadliest and most difficult cancers to treat. Therapy can eradicate the tumors, but most patients relapse within two years.
That time before relapse could eventually be extended. In a recent study, an experimental treatment was able to prolong remission significantly, offering hope to women who have exhausted conventional treatments.
"It's very exciting because we desperately need more good drugs to treat this deadly disease," says Dr. Jonathan S. Berek, a gynecological oncologist at UCLA's Jonsson Comprehensive Cancer Center who conducted a recent study of the therapy.
Normally, when a woman is diagnosed with ovarian cancer, she undergoes surgery to have the tumors removed. The ovaries, Fallopian tubes, uterus and parts of the bowel are often removed as well. Chemotherapy follows the surgery, and about 90% of patients then go into remission, a period of "watchful waiting."
"The problem is that over the next five to 10 years, as many as 90% of women will relapse and die," says Berek.
When the cancer returns, in other surrounding tissue, the cancer is more virulent and resistant to chemotherapy. But the new drug, OvaRex, works by "training the immune cells to ferret out the tumor cells and recognize them as foreign," says Dr. Christopher F. Nicodemus, a scientist at the company that makes OvaRex, Unither Pharmaceuticals in Wellesley Hills, Mass.
Normally, because tumors come from the same tissue as normal cells, the immune system doesn't recognize malignant cells as dangerous. However, ovarian cancer has an abnormal surface protein, or antigen, called the CA-125. The OvaRex antibody is programmed to latch onto this CA-125 protein, prompting an attack on cells with the markers.
In a test of 145 women with advanced cancer who had responded well to standard treatment, 73 received OvaRex, and the remainder received a placebo, or dummy pill. The women in the treatment group relapsed in an average of 24 months, versus almost 11 months in the placebo group. Patients also didn't experience any of the harsh side effects associated with chemotherapy, according to the study, which was presented this month at a meeting of the American Society of Clinical Oncology in Chicago.
Although OvaRex looks promising, scientists don't know if it will increase survival. They hope to answer that question in a new study, expected to involve more than 350 patients at 60 centers in the U.S., including UCLA and Cedars-Sinai Medical Center. Results won't be available for at least three years.
"But even if this is only effective at prolonging remission," says Berek, "it is still an important new agent."
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An estimated 25,400 American women will be diagnosed with ovarian cancer this year, according to the American Cancer Society, and about 14,300 will die of the disease.
Only about 25% of ovarian cancers are found at early, more curable stages. Most are diagnosed when the disease is advanced, and only about half of patients survive more than five years.
Ovarian cancer is difficult to detect because tumors are often deep in the ovaries, and there is no reliable test for the disease.
Women may undergo a transvaginal sonography, an ultrasound performed in the vagina. However, the ultrasound can only identify a mass in the ovary but can't predict whether it is cancerous.
Similarly, blood tests to measure CA-125, a protein that is increased in women with ovarian cancer, are not always accurate. Other ovarian diseases can boost levels of CA-125, while some ovarian cancers don't produce enough CA-125 to cause a positive test.
Another barrier to diagnosis is that its symptoms are common in other conditions.