CHICAGO — For the first time, doctors said yesterday that they have found a pill that improves survival for people with liver cancer, a notoriously hard-to-treat disease diagnosed in more than half a million people globally each year.

The results in a multinational study of 602 patients with advanced liver cancer are impressive and likely will change the way patients are treated, say cancer specialists, including the study authors. Patients got either two tablets daily of a drug called sorafenib or dummy pills in the study, which started in March 2005. Some patients are still alive, although on average, sorafenib patients survived 10.7 months versus almost 8 months for those on dummy pills.

That type of survival advantage “has never happened” with liver cancer “and is a major breakthrough in the management of the disease,” said Dr. Josep Llovet, the lead author.

“That may not sound like a lot of time,” but for liver cancer, “this is actually a quite impressive gain,” said Dr. Nancy Davidson of Johns Hopkins’s Bloomberg School of Public Health. “It is the first effective systemic treatment for liver cancer, which is such a huge problem internationally.”

The results were released yesterday at the American Society of Clinical Oncology’s annual meeting.

“We now have moved forward” in treating advanced liver cancer “when it was not really possible before,” Dr. William Blackstock of Wake Forest University School of Medicine said at a press briefing about the study.

Sorafenib attacks cancer with a targeted double-barreled approach. It zeroes in on malignant cells themselves and cuts off the blood supply feeding the tumor. It is believed to work on tumors within the liver and those that have spread elsewhere.

In the study, tumors didn’t shrink or disappear but in many cases, they also didn’t grow.

“You are not curing the disease but you are delaying the progression of the disease significantly and strikingly,” Dr. Llovet of Mount Sinai School of Medicine in New York and Hospital Clinic of Barcelona, Spain, said.