NEW YORK, (Reuters) – An experimental medicine  from Dendreon Corp improved survival in men with advanced forms  of prostate cancer, the company said yesterday, bolstering  chances of it becoming the first approved therapeutic vaccine  for any type of cancer.

Shares of Dendreon more than tripled in heavy morning  trading to as high as $22.10 and were up 138 percent at $17.38  in afternoon trade as the study results suggested a  revolutionary form of therapy is on the horizon for one of the  most common cancers.

Unlike traditional vaccines that prevent disease, the  company’s Provenge medicine treats it by stimulating the body’s  own immune system.

“If you’re in late stages of prostate cancer and your  doctor says, ‘You’ll have no side effects with this drug and it  will probably extend your life,’ who’s not going to take it?”  said Sven Borho, an analyst with OrbiMed Advisors.

The Phase III clinical trial met the main study goal of  improving survival, prompting Dendreon to say it will seek U.S.  regulatory approval of Provenge in the fourth quarter.

“The successful outcome from the Phase 3 IMPACT study  provides validation of the long-pursued goal of harnessing the  human immune system against a patient’s own cancer,” Dendreon  Chief Executive Mitchell Gold said in a statement.

Prostate cancer is the most common cancer in American men  other than skin cancers, according to the American Cancer  Society. About one in six men will be diagnosed with prostate  cancer during his lifetime.
Paul Latta, an analyst with McAdams Wright Ragen, said  Provenge stood to be a $200 million product if it is approved  only in the advanced prostate cancer patient group, but could  expand to a $1 billion blockbuster if it is expanded to men  with earlier stages of the disease.

But Borho, whose New York investment firm owns 2.5 million  shares of Dendreon, said Provenge’s annual sales could reach  several billion dollars.

“Dendreon has delivered the goods for sure, this is very  exciting,” Borho said.

Aside from OrbiMed, other big institutional shareholders  included BAM Capital, Barclays Global Investors, Visium Capital  Management and Vanguard Group, according to Reuters data.