The Food and Drug Administration (FDA) has approved Dendreon Corporation’s Provenge, a “vaccine” that uses a patient’s own immune system to fight advanced prostate cancer that is no longer responding to hormone therapy. While not expected to be a cure, the news offers hope to men with advanced disease, many of whom have few treatment options available to them.
It’s been a rocky road to approval. In 2007, the FDA refused to approve the initial drug application, requesting more information about whether the drug prolongs survival. In 2009, Dendreon submitted the drug again, this time with more data.
Today’s green-light is based primarily on results from a randomized phase III study showing that men who received Provenge infusions lived an average of about 4 months longer than men who were getting the placebo (26 months versus 22 months).
Patients receiving Provenge reported few side effects, and those they did report — chills, fever, headache, fatigue, nausea, joint aches, and back pain — usually went away within a few days.
The vaccine is made by removing some of a patient’s white blood cells and sending them to a lab, where they are activated by exposing them to a protein found on prostate cancer cells. The cells are then given back to the patient about 3 days later, in a process similar to a blood transfusion. This is done 3 times, with about 2 weeks in between each dose.
“Provenge suggests that we may in fact be able to stimulate our body’s own defense mechanisms to aid our fight against cancer. This in itself is a truly remarkable accomplishment,” said Len Lichtenfeld, MD, deputy chief medical officer of the American Cancer Society. “It also opens the door for — and reignites interest in pursuing — the development of other vaccines for other types of cancer, including melanoma and breast cancer.”
“However,” Lichtenfeld says, “it’s important to keep in mind that this vaccine isn’t for all men with prostate cancer, only a particular group. Not all men with prostate cancer will benefit from Provenge.”
Men with advanced prostate cancer often have few treatment options available to them. Drugs that affect the body’s hormone levels are often effective for a time, but eventually the cancer stops responding to them. Provenge was approved for use against these cancers. Chemotherapy can also help some men at this point, but can have its own serious side effects.
Progress — but with some caveats
While the Provenge approval represents an important step forward in cancer treatment, Lichtenfeld says, there are some concerns.
For one, while Provenge improved survival, there was no evidence that the drug slows progression of the disease. However, Lichtenfeld says, “the data was enough to convince the FDA that the survival benefit was genuine.”
Also, with many men facing late-stage prostate cancer and thousands of deaths from prostate cancer every year, there may be a large demand for the vaccine, and it’s not clear how the company will handle this.
And there’s the issue of cost. While official numbers haven’t been disclosed, the drug is expected to be very expensive. It’s also not clear how Medicare will handle coverage of the drug.
Still, Lichtenfeld says, “the bottom line here is that Dendreon was successful in doing something that we’ve been hoping for for a long time, and that’s good news. While the survival benefit was very limited, this represents a very important step forward in cancer treatment.”