CHICAGO (AP) – A new but unproven theory says body heat might explain Lance Armstrong’s astounding victory over testicular cancer.

The theory – disputed by Armstrong’s doctor – refers to the unusually high cure rate for testicular cancer, even when it has spread to other parts of the body.

This form of cancer was highly treatable even before Armstrong was diagnosed in 1996. However, his public battle with the disease and seven subsequent Tour de France triumphs put a special spotlight on his recovery.

According to three Johns Hopkins University researchers, the reason for the good prognosis might have to do with the fact that the temperature of the testicles is a few degrees cooler than the rest of the body. That’s to enhance development of sperm, but it might also make cancer that develops there sensitive to heat, the researchers said.

And so, their not-yet-mainstream theory goes, when testicular cancer spreads to other, warmer body parts, the higher temperature might damage it and render it more vulnerable to cancer treatment.

Understanding the basis for what they call “the Lance Armstrong effect” might lead to ways to help make other kinds of cancer more treatable, the researchers said in an article in Wednesday’s Journal of the American Medical Association.

Skeptics include the American Cancer Society’s Dr. Michael Thun, who called the idea “total speculation,” and Dr. Craig Nichols, Armstrong’s doctor.

“There is no direct or even indirect evidence even remotely supporting this hypothesis,” said Nichols, a specialist at Oregon Health & Science University’s Cancer Institute.

The American Cancer Society estimates that 8,250 men will be diagnosed with testicular cancer this year.

The five-year survival rate is more than 95 percent, even when the disease has spread to nearby lymph nodes, and 72 percent when it has spread beyond.

Armstrong’s disease had spread to his abdomen, lungs and brain. He was declared cancer-free after treatment that included surgery and chemotherapy.

Nichols said the biological makeup of testicular cancer makes it unusually sensitive to the cancer drug cisplatin, which has been around for about 30 years.

But the Johns Hopkins researchers – Donald Coffey, Robert Getzenberg and Dr. Theodore DeWeese – say their theory isn’t so far-fetched.

Their article references studies that used heat to treat other tumors, including cervical cancer. Heat therapy is used in a handful of cancer centers around the country, and scientists are investigating the best way to selectively deliver heat to cancer cells. Johns Hopkins is among centers where researchers are testing potential methods in animals.

Dr. Donald L. Trump, associate director of the Roswell Park Cancer Institute in Buffalo, N.Y., said the idea is potentially plausible. But it’s also possible that testicular cancer cells are particularly vulnerable to stress other than heat. And said Trump, it’s worth studying to find out.