SACRAMENTO, Calif. - Gov. Jerry Brown is being treated for early stage prostate cancer but will stay on the job throughout his nearly four-week treatment, his office said Wednesday, calling the typically energetic 74-year-old chief executive's prognosis "excellent." Brown's office gave few details about his treatment or how Brown was found to be suffering from the most common cancer to afflict men, but said in a statement that he would undergo conventional radiotherapy until the week of Jan. 7 for what it called a "localized" cancer. The three-term governor's "prognosis is excellent, and there are not expected to be any significant side effects," University of California, San Francisco oncologist Eric Small said in the statement. Small is Brown's oncologist. Brown's spokesman Gil Duran declined further comment. Localized prostate cancer means "the tumor is still contained within the prostate," said Dr. Mark Litwin, chairman of the UCLA Department of Urology, who is not involved in Brown's care. Of course, that's what you want because you can treat it much more effectively. For early stage prostate cancer, the typical radiation treatment is five days a week for four to five weeks, said Dr. Ralph de Vere White, urological oncologist and director of the University of California, Davis Comprehensive Cancer Center in Sacramento. Other oncologists said the treatments can sometimes last up to nine weeks. Not all men who are diagnosed with the disease choose to undergo treatment, and doctors advise patients to consider the risks. Those who undergo radiation are typically subjected to a series of high-intensity beams of radiation aimed directly at the prostate, a procedure similar to undergoing an X-ray that can take less than half an hour. De Vere White, who is not involved in Brown's case but said given the governor's apparent good health, it would be an easy decision to do the radiation treatment. If you are healthy, as the governor appears to be, "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. It is the governor's second experience 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. For that cancer, Brown underwent micrographic surgery, in which a doctor can tell even before the wound is closed that all the cancerous cells have been removed. More than 241,000 new cases of prostate cancer 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. The governor's office did not say how the prostate cancer was first detected. Cases are typically found through a PSA blood test or a physical exam. He previously was governor from 1975 to 1983, and returned to his former post in 2011 after handily beating former eBay chief executive Meg Whitman. Brown became the state's oldest serving governor when he turned 73 a few months into office. He was its second youngest when he was first sworn into office in 1975. Brown is coming off a resounding political victory in November after he persuaded Californians to support Proposition 30, a ballot measure that raised the statewide sales tax and increased income taxes for the wealthy. The extra revenue is expected to help ease the state's budget woes and give Brown smoother sailing to pursue his agenda in 2013.