It all began last November, when Kerry started a series of medical exams for the purposes of his presidential run, the junior senator from Massachusetts said. A colonoscopy at Georgetown Medical Center "came up completely clean," Kerry said, using an unfortunate choice of words, but a blood test with the Senate physician indicated that his "protein specific antigen," or PSA, had risen from 2.7 nanograms per milliliter the year before to 3.2. Two years before it had been 2.0.

Kerry's wife, Teresa Heinz Kerry, noticed the elevated rates and became alarmed.

"Teresa is a hawk on health issues," says the source close to Kerry. "She just went through the whole dying process with her mother." Additionally, the friend said, while in the past Kerry might have been inclined to not visit a doctor, "Kerry's gone through this whole period of introspection anyway, with his run for the presidency, his father died a few years ago, his mother died a few months ago. So these kinds of issues had become important to him."

Because the earlier PSA test had taken place at a Massachusetts General Hospital lab, the Senate physician suggested that Kerry return to that lab for another test. He did, and that test reported on Dec. 19 that he had a PSA level of 3.4.

"The PSA is a marker that can indicate cancer," says Dr. Dorado Brooks, director of prostate cancer for the American Cancer Society. "But it can also be related to benign conditions." Brooks says that "that sort of rise over a relatively short period of time" is a red flag for possible cancer.

The next day, Kerry underwent a biopsy at Massachusetts General Hospital. Four days after that, on Christmas Eve day, Kerry was told that the biopsy tested positive. He was told, however, that because the cancer had been caught so early, a complete cure was possible. A Jan. 2, 2003, full-body scan indicated that the cancer had not spread, or metastasized.

Five days later, Kerry met with Dr. Walsh -- Kerry called him a "superb pioneering surgeon" Tuesday -- with whom he discussed the various treatment options.

There is no "clear and unequivocal evidence that one kind of treatment is better than another," Dr. Dorado Brooks says. Prostate cancer survivors like former presidential candidate and Sen. Bob Dole, R-Kansas, former Desert Storm Gen. Norman Schwarzkopf, FBI director Robert Mueller III, Yankees manager Joe Torre, and former 007 Roger Moore all have opted for surgery.

On the other hand, Nelson Mandela, Charlton Heston, Rupert Murdoch and former New York City Mayor Rudolph Giuliani chose radiation therapy instead.

Asked if he opted for surgery rather than radiation treatment because the former would presumably allow him to return sooner to the campaign trail, Kerry said: "For my age, for my level of detection, for my current analysis of what the slides look like, this is the best course of action." He took the facts about the surgery's potential side effects "and the extraordinarily enhanced recovery rate, and measured that against the outcome of the radiation and against my father's own outcome, and I made a judgment that it is better to get this thing out of me."

The source close to Kerry said he "wants to put it behind him, he wants to move on. And yes, he wants to campaign -- that's a factor."

Walsh is one of the leading prostate surgeons in the world. "He has broken through with what they call nerve- sparing surgery," Kerry said Tuesday, "which reduces bleeding and maximizes the long-term curable possibilities." But bleeding has little to do with the nerve-sparing surgery's raison d'etre -- it provides a great likelihood that the patient will be able to again achieve an erection.

The prostate gland, which lies under the bladder and just in front of the rectum, manufactures an alkaline fluid that makes up about a third of ejaculate. Radical prostatectomies used to be very bloody operations that carried with them great risk of long-lasting side effects -- namely incontinence and impotence. It was accepted as medical fact that the nerves that control erections ran through the prostate and prostate cancer surgeries would therefore always leave the patient impotent. Walsh began to wonder about this, however, after one of Walsh's patients reported that he had regained his ability to have an erection after his surgery. At a medical convention in the Netherlands in 1982, Walsh met a retired urologist named Pieter Donker, who invited him to join him in a dissection of a stillborn infant since Donker had discovered that stillborns were excellent subjects for prostate study because the nerves were easier to see. During this dissection, Walsh noticed that the nerve bundles were not inside but outside the prostate capsule. In April 1982, Walsh performed the first "nerve-sparing" prostatectomy on a 52-year-old man, who regained his ability to have an erection within a year. Walsh has since performed thousands of these operations, with the vast majority of patients experiencing neither incontinence nor impotence in the long term.

That is the option Kerry chose. "I am convinced the choice I made is the right choice for me," he said, before warning several men in the press gallery that they may have prostate cancer as well. "I don't want to shock anybody here, but for those men here, the probability is that some of you have it today and don't know it."

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