June 29, 2015 -- Medicines that help our immune system fight off tumors are showing early success in a widening variety of cancers.
Some of the drugs, known as immunotherapy, have already been approved to treat several cancers, including advanced melanoma and a type of lung cancer. Studies have shown they can help treat not only tumors such as those in breast and colon cancer, but also blood cancers like multiple myeloma and Hodgkin lymphoma.
The drugs are expensive, and experts caution they're far from a cure. Still, hundreds of studies are underway to test how effective they are. Researchers recently talked about some of these studies at the American Society of Clinical Oncology conference:
- Keytruda (pembrolizumab), approved last September for advanced melanoma, helped people with advanced head and neck cancer, an incurable disease with a poor prognosis.
- Opdivo (nivolumab), was approved for advanced melanoma last December and for squamous, non-small-cell lung cancer in March. It was found to extend survival of people with squamous, non-small-cell lung cancer, which represents about 25% of all lung cancers.
- Opdivo also showed promise in advanced liver cancer, which has only one FDA-approved treatment. In a small study of the drug, tumors in about 20% of people with liver cancer shrunk at least 30%.
Also, two early studies presented in December at the American Society of Hematology meeting found Opdivo shows promise in people with Hodgkin lymphoma who'd tried other treatments, including stem cell transplants, without success.
"It’s looking like there’s no type of cancer in which some patient won’t benefit from these immune approaches,” says Richard Schilsky, MD, chief medical officer at the American Society of Clinical Oncology.
Research Paying Off at Last?
But “despite all of the efforts... there were really no significant breakthroughs that made a real difference in the lives of patients with cancer,” says Len Lichtenfeld, MD, deputy chief medical officer for the American Cancer Society. He worked at the National Cancer Institute in the early 1970s.
The problem was getting the drugs to attack only tumor cells and not healthy tissue.
Finally, all the hard work in this field over the years appears to be paying off, Lichtenfeld and Schilsky say.
In 2011, the FDA approved the first "checkpoint inhibitor" drug, Yervoy (ipilimumab), for melanoma that couldn’t be removed surgically or had spread to other parts of the body.
Yervoy, Keytruda and Opdivo are all so-called checkpoint inhibitors. They work by blocking immune cell molecules called “checkpoint proteins.”
These proteins are like the brakes on the immune system. They keep the immune system from going overboard and attacking normal tissue, as happens in autoimmune diseases like rheumatoid arthritis and lupus. Tumors can fool checkpoint proteins into thinking that they are normal tissue, so they fly under the immune system’s radar.
“The immune system was designed by nature to recognize foreign things in the body,” Schilsky says. “Every cancer is a foreign object. It’s only a question of how foreign it appears to be so that the immune system can recognize it.”
All three drugs have side effects, but Opdivo and Keytruda appear to have fewer than Yervoy, Schilsky says. Side effects for Opdivo included rash, itching, cough, and retaining fluid, according to the FDA. Keytruda side effects included fatigue, cough, nausea, joint pain, constipation, and diarrhea, the agency says.
Lichtenfeld says experts still have a lot more to learn about the safety and effectiveness of immunotherapy drugs, though.
When Keytruda was approved, the FDA said it helped shrink tumors in 24% of patients. The effect lasted at least 1.4 to 8.5 months, but lasted longer than that in most people, the agency said.
Opdivo helped shrink melanoma tumors in 32% of patients, and the effect lasted more than 6 months in about a third of those people.
The drugs are also expensive. Schilsky says they can cost $10,000 to $20,000 a dose and are given every other week.
And even though the drugs are promising for other conditions, the cost might prevent them from being prescribed off-label, meaning used for treatment before being FDA-approved for that purpose. Insurance companies are not likely to pay for that use, Schilsky says.