There's a mystery to cancer, in large part because of fear, that PBS tries to unravel in next week's six-hour documentary "Cancer: The Emperor of All Maladies."

"We're not really honest with each other," filmmaker Ken Burns said. "We know about heart disease. We know about diabetes. We know about other things, but there's a kind of resistance because cancer is so scary."

Burns, who was 11 when his mother died of breast cancer, is executive producer of the film, directed by Barak Goodman. It's one of the few times Burns has been involved in a project that he didn't instigate.

The film airs over three consecutive nights beginning on March 30 and is inspired by Dr. Siddhartha Mukherjee's Pulitzer Prize-winning book of the same title. Starting at its most elemental — how cancer got its name — the documentary tells the story of advances and setbacks in years of research on how the disease develops and is treated, through developments since Mukherjee's book was published in 2010.

Mukherjee sees it as a State of the Union address on cancer, a topic with a reach and complexity that can make the entirety of the federal government seem simple in comparison.

The film softens the science with individual stories of people fighting for their survival.

Cancer proves an elusive and resilient enemy. Much of the promising research has been done since the 1970s, establishing that the cell mutations that characterize the disease can be triggered by genetics, the environment or a virus. Treatments that once seemed promising proved disappointing. Some had limited success. Immunotherapy, the use of a person's own immune system to fight cancer cells, is so new that it barely received a mention in Mukheerjee's book but gets a thorough telling in the film.

The film follows the story of the very first child ever to receive a new treatment to attack cancer cells.

"The history of cancer has been littered with false dawns with, as our film discusses, moments of great optimism followed by immediately crashing disillusionment," Goodman said. "So we did have to be very careful about those we chose to follow."

Often, the doctors and scientists are pushed by patients themselves. The story of radical mastectomy for breast cancer is particularly illuminating, how it went from the universally accepted treatment with naysayers ridiculed until other, less invasive approaches were proven effective.

The film discusses the groundbreaking surgeon general's report in the 1960s strongly linking cigarette smoking to cancer and the slow but steady reduction, at least in the United States, of probably the best-known carcinogen.

"You could say, 'Does that matter?'" Mukherjee said. "Trust me, in the next 10 years we will find yet another new carcinogen being somewhere that we don't know about and a company that's eager to obfuscate on its origins, and the lessons from what we learned about cigarettes will apply all over again."