Renowned Conductor, Battling Brain Cancer, Steps Down From Orchestra

The conductor Michael Tilson Thomas announced on Wednesday that he would step down as artistic director of the New World Symphony, a prestigious training orchestra for young artists in Miami that he helped found, as he battles an aggressive form of brain cancer.

Saying he was “taking stock of my life,” Thomas, 77, the former music director of the San Francisco Symphony, said he was reducing his administrative duties to focus on his health.

“I now see that it is time for me to consider what level of work and responsibilities I can sustain in the future,” he said in a statement.

In the statement, Thomas provided for the first time details about his condition, which he announced last summer, when he canceled a series of engagements. He said he had glioblastoma, one of the most lethal forms of brain cancer; had undergone surgery last year to remove a tumor; and had also received chemotherapy and radiation treatments.

“Currently the cancer is in check,” he said. “But the future is uncertain as glioblastoma is a stealthy adversary. Its recurrence is, unfortunately, the rule rather than the exception.”

The New World Symphony, where Thomas will remain artistic director laureate, praised the “genius of his vision and the strength of his leadership” in a statement, in which the chairman of its board, Will Osborne, said, “We are honored to have his continued presence and involvement.”

Thomas said he planned to continue conducting in the United States and Europe. In the coming months he is scheduled to lead more than two dozen concerts, including with the National Symphony Orchestra, the Cleveland Orchestra and the London Symphony Orchestra. On May 6 and 7 he is scheduled to be in Miami to lead the New World Symphony in the Fifth Symphony of Mahler, one of his specialties.

Since his surgery, Thomas has led 20 concerts, appearing with the San Francisco Symphony, the Los Angeles Philharmonic and the New York Philharmonic. Audiences have greeted him with hearty ovations, and he has seemed relatively energetic.

“I will continue to compose, to write and to mull over your thoughts and mine,” Thomas said in his statement. “I’m planning more time to wonder, wander, cook and spend time with loved ones — two-legged and four-. Life is precious.”