Casino magnate and Republican Party megadonor Sheldon Adelson is stepping away from his Las Vegas Sands Corp. for cancer treatment, leaving his company amid economic uncertainty in the global gambling industry due to the Covid-19 pandemic.

Mr. Adelson, 87 years old, founded Las Vegas Sands and continued leading the company after being diagnosed with non-Hodgkin lymphoma, which the company announced in March 2019. The billionaire is taking medical leave to resume his cancer treatment.

Mr. Adelson, whose family is majority owner of the company, has said his succession plan is for the current executive team, including 25-year Sands veteran Robert Goldstein and Mr. Adelson’s son-in-law Patrick Dumont, to lead the company, according to a person familiar with the conversations.

Mr. Goldstein, who most recently was chief operating officer and president, was named by Sands’s board of directors as acting chief executive and chairman during Mr. Adelson’s medical leave, the company said Thursday. Mr. Dumont joined the company in 2010 and is chief financial officer and executive vice president.

Las Vegas Sands operates casino-resorts on the Las Vegas Strip, in the Chinese territory of Macau and in Singapore. As Covid-19 first swept around the world last year, casino closures and pandemic restrictions wiped out gambling company revenues. Las Vegas Sands’s revenue plummeted 82% in the third quarter of last year compared with the same quarter of the previous year.