Brown, 74, is receiving a short course of conventional radiotherapy for "localized prostate cancer," the statement said.
Brown's "prognosis is excellent, and there are not expected to be any significant side effects," University of California, San Francisco oncologist Eric Small said.
The radiation treatment will be completed the week of Jan. 7, nearly four weeks from now, and Brown will continue to work a full schedule, the statement said.
Brown's spokesman Gil Duran declined further comment.
It is the governor's second bout with cancer. He underwent minor surgery in spring 2011 to remove a cancerous growth on his nose. He was put under local anesthetic and doctors removed basal cell carcinoma, a common, slow-growing form of skin cancer, from the right side of his nose.
The governor underwent a type of surgery known as Mohs, or micrographic surgery, in which a doctor can tell even before the wound is closed that all the cancerous cells have been removed.
Prostate cancer is the most common cancer in men. More than 241,000 new cases are expected to be diagnosed in the United States this year. More than 90 percent are early stage, and nearly all men with such diagnoses survive at least five years.
Typical radiation treatment for an early stage prostate cancer is five days a week for four to five weeks, said Dr. Ralph de Vere White, urological oncologist and director of the UC Davis comprehensive cancer center in Sacramento.
Not all men who are diagnosed with the disease choose to undergo treatment, and doctors advise patients to consider the risks.
De Vere White, who is not involved in Brown's case, said given the governor's otherwise excellent health, it's an easy decision to do the radiation treatment.
"When you're as healthy as the governor is, and you are looking out at 10 years, then you go for a treatment that is going to have in excess of a 97 percent cure rate," he said. "It really should have very minimal side effects, should have minimal to no interference with his life, and kind of represents the reason why people advocate for finding this disease early."
The governor's office did not say how the prostate cancer was first detected.
Brown is the son of former two-term Gov. Edmund G. Brown and has spent a lifetime in politics, including terms as the secretary of state, attorney general and mayor of Oakland.
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