CLEVELAND (AP) — Franz Welser-Möst will retire as music director of the Cleveland Orchestra in June 2027, ending a 25-season tenure that will be the longest in the ensemble’s history.

The orchestra said in September that the 63-year-old had a cancerous tumor removed and he was canceling conducting performances from late October through the end of the year. At the time, the orchestra said he would undergo treatment between conducting engagements for 12 to 16 months.

Welser-Möst was to conduct the Orchestra at Severance Hall starting Thursday night and is to lead it on tour to New York’s Carnegie Hall on Jan. 20 and 21.

“I am immensely grateful for the extraordinary journey that I have had with the Cleveland Orchestra since I first came to Severance more than 30 years ago,” Welser-Möst said in a statement Thursday. “It is both a special and an emotional moment as I reflect on what we have accomplished together. But perhaps what matters most to me is the shared passion, the inspiring creativity, and the lasting friendships that I have had the privilege of building with our musicians, audiences, and fans around the world.”

Born in Austria, Welser-Möst was principal conductor of the London Philharmonic Orchestra from 1990-96, chief conductor of the Zurich Opera from 1995-2005 and its general music director from 2005-08. He was general music director of the Vienna State Opera from 2010-14.

Welser-Möst first conducted the Cleveland Orchestra in 1993 and became music director for the 2002-03 season following Christoph von Dohnányi’s 18-season tenure. Welser-Möst’s time leading Cleveland will surpass that of George Szell, the orchestra’s music director from 1946-70.