April 22 (Bloomberg) -- It's retirement season at the U.S. Supreme Court. The question is whether Chief Justice William Rehnquist has marked the occasion on his calendar.

Rehnquist, 80, was the focus of retirement speculation even before he revealed in October that he has thyroid cancer. That talk will intensify over the next 10 weeks as the court approaches the end of its term, the self-imposed deadline that some of his predecessors have used to announce their departures.

While conventional wisdom among court watchers continues to favor a retirement, Rehnquist's March 21 return to the bench caused some cancer experts to upgrade their assessments of his condition. The bottom line: Even people who know the chief justice can't be sure of his intentions.

``Nobody really knows,'' said Washington litigator Charles Cooper, who clerked for Rehnquist in 1978-79 and, as a Justice Department official, helped persuade President Ronald Reagan to elevate him from associate justice to chief justice in 1986. ``He knows. But I honestly don't think anyone else really knows.''

The next chief justice will be only the 17th in the nation's history, with the potential to shape the Supreme Court's agenda for two decades. And with Republicans and Democrats already clashing over lower-court nominees, President George W. Bush's pick to succeed Rehnquist would face an almost certain confirmation fight.

Activists on both sides are planning to spend millions of dollars on the anticipated battle -- if not over a Rehnquist retirement, then over a possible departure by 85-year-old John Paul Stevens, 75-year-old Sandra Day O'Connor or some other justice.

Prognosis Unclear

Much of the uncertainty centers on Rehnquist's medical prognosis. In statements last year, the court said Rehnquist had undergone a tracheotomy and was being treated with chemotherapy and radiation.

Those treatments led a number of prominent cancer specialists to conclude that he probably has anaplastic thyroid cancer, a rare and especially aggressive form of the disease that leaves many patients with only a few months to live.

That diagnosis would explain why the court has offered no indication that Rehnquist's thyroid gland was removed, as probably would have been the case with a more localized cancer, said James Fagin, director of the endocrinology division of the University of Cincinnati's Department of Internal Medicine.

``The original speculation is still the most likely one: that he has undifferentiated, or anaplastic, cancer,'' Fagin said.

Second Thoughts

Other cancer experts are having second thoughts in light of the six months Rehnquist has now survived. That suggests he might be among the vast majority of thyroid-cancer patients --98 percent, according to one study -- who have a non-anaplastic variety, said Steve Sherman, chairman of the endocrine neoplasia department at the University of Texas's M.D. Anderson Cancer Center in Houston.

``Certainly, I think that fits with the statistical likelihood, which is that he didn't have anaplastic cancer,'' Sherman said. ``The longer that he survives and is doing well, the better the overall prognosis will be. One has to be encouraged that he has resumed what appears to be a fairly normal level of activity.''

Rehnquist is again working from the court every day and appears stronger than he did at the Jan. 20 presidential inauguration, when he stayed only 15 minutes after administering the oath of office. Although his speech is altered from the tracheotomy tube that remains in his throat, he has been an active questioner in the 15 hours of argument the court has heard since his return to the bench.

Beating the Odds?

Another medical possibility is that Rehnquist, even if he has the anaplastic variety, is simply beating the odds. Although the average survival time for anaplastic thyroid cancer is about six months, in exceptional cases patients can live for years.

``There are people who, no matter how serious their cancer, turn into long-term survivors,'' said Herman Kattlove, a Los Angeles oncologist and medical editor for the American Cancer Society. ``They're rare, but you can't count them out.''

Of course, Rehnquist may opt to retire even if he does appear to be beating the cancer. With 33 years of service --more than half as chief justice -- he has served longer than all but seven previous members of the court.

And Rehnquist, a former Justice Department official in the administration of President Richard Nixon, who named him to the court, may seize on the chance to have his replacement chosen by a Republican president and Republican-controlled Senate.

No Hints

The chief justice, for his part, is offering no hints, conducting the court's business much as he has for decades. Court spokeswoman Kathy Arberg said the chief justice had no comment on his plans. He has hired law clerks for the 2005-06 term, which starts in October, although he did so well before the cancer diagnosis.

``No one can say for sure,'' said Elliot Mincberg, legal director for the People for the American Way, a Washington-based group that opposes several of Bush's lower-court nominees. ``But in light of his health and the age of a number of justices, it's highly likely that there will be at least one, and maybe more than one, vacancy this year.''

To contact the reporter on this story: Greg Stohr in Washington at gstohr@bloomberg.net.

Last Updated: April 22, 2005 00:05 EDT