The difference in the drug's early success may lie in the approach it takes in delivering targeted cancer therapy. Cancer researchers have been chasing more targeted ways to deliver cancer treatments for decades now, in search of a method more refined than the "slash, burn and poison" approaches available with traditional surgery, radiation and chemotherapy. Usually, targeted therapies home in on a particular part of the cancer itself – a particular kind of cell or a process vital to a tumor's survival.
The current drug is a different because it targets the body's own immune system, training it to recognize tumor cells as foreign, malicious agents.
"In spite of everything we've done so far with cancer drugs, chemotherapy and the rest, what could be more powerful than having the body's own immune system attack the cancer?" said Dr. Roy Herbst, chief of medical oncology at Yale Cancer Center.
Still, doctors remain cautiously optimistic about the drug's early promise.
"In all new studies, there's usually a lot of optimism and hope, but this should all be tempered with a dose of realism," Brooks said. "What's initially reported may not necessarily pan out with time."