A certain type of prostate cancer considered inoperable might be operable after all -- and, thus, curable, according to recent research.

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A study of more than 5,600 men from the Mayo Clinic suggested that cT3 prostate cancer, a disease in which the cancer spreads from inside the prostate to immediately outside it, is operable and has 15-year cancer survival rates of almost 80 percent.

"These patients have a better chance if they undergo surgery and are living longer than if they undergo radiation therapy," said Dr. Horst Zincke, a Mayo Clinic urologist and the study's lead author.

Researchers said treatment of this type of prostate cancer has been controversial because it is a third-stage cancer in which the malignancy has spread.

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Due to its advanced stage, some doctors have considered it inoperable via radical prostatectomy, Zincke said in a news release.

"It's considered inoperable by some urologists and referred to radiation oncology," Zincke said. "They think surgery can't be done because the cancer is outside the prostate. Currently, only 15 percent are referred for surgery."

Researchers said the problem with radiation therapy is the cancer survival rate: 79 percent in only five years. In contrast with radical prostatectomy, 79 percent of the patients lived at least 15 years, Zincke said.

Zincke said that when malignant prostate tumors are more aggressive, they are not especially responsive to radiation therapy alone.

Surgery alone may be sufficient treatment for those without lymph node involvement. But hormone therapy or radiotherapy may become necessary for others.

Zincke said patients suffering from cT3 prostate cancer should seek a surgeon who performs at least one prostate surgery per week and has completed at least 300 prostate surgeries. He said only 3 to 4 percent of urologists currently perform prostate cancer surgeries regularly.