Justice Ruth Bader Ginsburg announced Friday that she is being treated for a recurrence of cancer, this time on her liver, but says she is able to maintain her workload on the Supreme Court and has no plans to retire.

“I have often said I would remain a member of the court as long as I can do the job full steam,” Ginsburg said in a written statement. “I remain fully able to do that.”

Still, the cancer recurrence and the question of how long the 87-year-old Ginsburg might remain focused new attention on how the Supreme Court’s future could be controlled by the winner of November’s election.

President Trump has pitched the prospect of replacing the court’s liberal justices as a selling point for his reelection, and said adding another conservative to the court will transform its abortion jurisprudence and protect gun rights.

Ginsburg, the court’s oldest member, has battled cancer four previous times and has had other health concerns. She was in Johns Hopkins Hospital in Maryland earlier this week for an unrelated infection related to her gallbladder.

Her past resilience caused doctors not involved in her treatment to hedge their reactions to what clearly was bad medical news.

James M. Cleary, an oncologist at Dana-Farber Cancer Institute in Boston, said that Ginsburg’s age and extensive cancer history make it difficult to predict whether she will fare better or worse than the average person.

“This is a patient whose cancer has been an outlier,” he said. Still, he described Ginsburg’s cancer battles as inspirational, saying she has “given my cancer patients a lot of hope, how well she’s done.”

In her statement, Ginsburg said doctors discovered lesions on her liver in February. She started immunotherapy, but it proved unsuccessful, so she began chemotherapy in mid-May, she said. A subsequent scan on July 7 indicated “significant reduction” of the lesions and no new disease, she said.

“I am tolerating chemotherapy well and am encouraged by the success of my current treatment,” Ginsburg said. “I will continue bi-weekly chemotherapy to keep my cancer at bay, and am able to maintain an active daily routine. Throughout, I have kept up with opinion writing and all other court work.”

Ginsburg’s description of the cancer as a “recurrence” and the use of the chemotherapy drug gemcitabine indicated that the newly discovered lesions on her liver are the result of the pancreatic cancer with which she was diagnosed last year, several oncologists said.

“The treatment she is getting is typical for pancreatic cancer. That would fit,” said John L. Marshall, director of the Ruesch Center for the Cure of Gastrointestinal Cancers at Georgetown Lombardi Comprehensive Cancer Center. “But her cancer history is very unusual, from a good perspective. She’s always done much better than one would have anticipated.”

People with the disease Ginsburg is battling typically live another 12 to 18 months, Marshall said. But because Ginsburg’s cancer history is so unusual, she may defy those expectations, he said. The justice has endured two battles with pancreatic cancer 10 years apart — a rare course for that disease — as well as colon and lung cancer.

Another oncologist, Mark Lewis, director of gastrointestinal oncology at Intermountain Healthcare in Salt Lake City, noted that gemcitabine should have no impact on Ginsburg’s mental acuity as she continues working.

Lewis said he was encouraged by Ginsburg’s announcement that the lesions on her liver have shrunk because of the chemotherapy. He said that occurs in perhaps 25 percent of these cases.

Ginsburg’s health has been a continuing source of concern during recent years. If she were unable to do her job, it would leave the court’s four liberals without its leader. It would also give Trump a chance to name a third member of the court, and cement its conservative majority for a generation.

Senate Majority Leader Mitch McConnell (R-Ky.) blocked then-President Barack Obama from making an election-year appointment to the Supreme Court in 2016. He denied Obama’s nominee, Judge Merrick Garland, even a confirmation hearing, saying the next president should make the choice.

But McConnell has said he would push through a Trump nominee this year should an opening occur. The difference from 2016, he maintains, is that now the same political party controls the White House and Senate.

Trump has named justices Neil M. Gorsuch and Brett M. Kavanaugh to the high court.

Ginsburg resisted calls to retire when Obama was president, to give him a chance to name her replacement. During the 2016 campaign, she expressed her disdain for Trump — remarks she later said were inappropriate from a justice. But it has been clear she is not eager to have the president name her successor, and Democrats and other liberals have called on her to hold on through the election.

Should Trump’s presumptive opponent, former vice president Joe Biden, win the presidency, his replacement of Ginsburg and perhaps Justice Stephen G. Breyer, who turns 82 next month, would not change the court’s ideological balance. But it would replenish the liberals with a new generation. Biden has said he would nominate the Supreme Court’s first female African American justice.

Ginsburg has bounced back from each of her health scares in the past. During an appearance at the end of August, Ginsburg said that her work on the Supreme Court has “kept me going” through her battles with cancer and that she was “on my way to being very well.”

She kept up her share of opinion writing during the term just concluded, and was an active questioner during the court’s oral arguments. She participated in one teleconferenced hearing in May from her hospital bed.

Supreme Court justices choose what they reveal about their health. Chief Justice John G. Roberts Jr. recently confirmed he was hospitalized overnight after a fall last month only after The Washington Post learned about the incident separately.

Ginsburg said she was disclosing her new cancer diagnosis because she is “satisfied that my treatment course is now clear.”

In August, Ginsburg said that she had completed a three-week course of stereotactic ablative radiation therapy — a highly focused treatment that concentrates an intense dose of radiation on a tumor — after a malignancy was discovered on her pancreas.

That had been the second treatment for cancer in nine months for Ginsburg. She had a portion of her left lung removed in December 2018 and in past decades was treated for colon and pancreatic cancer. She broke ribs in a fall in November 2018, which resulted in the discovery of the lung cancer.

But before a roaring crowd at the National Book Festival in Washington at the end of last summer, she declared: “This audience can see that I am alive.”

Earlier this week, Ginsburg was admitted to Hopkins after experiencing a fever and chills. The court said she was given an endoscopic procedure “to clean out a bile duct stent that was placed last August.” It is unrelated to the cancer, and Ginsburg went home earlier than had been predicted.

Ginsburg was nominated to the court in 1993 by President Bill Clinton. She is the second-longest-serving justice, after Justice Clarence Thomas, one of the court’s five conservatives.