King Charles III and Queen Camilla will attend an Easter service at the chapel at Windsor Castle on Sunday, Buckingham Palace officials said.

The appearance will be the first major event for Charles, 75, since he was diagnosed with cancer in February.

Officials said Tuesday that Charles and Camilla will be accompanied by other members of the royal family at the Easter Sunday service at St. George’s Chapel.

The king is undergoing regular treatments and has suspended almost all his public engagements since his cancer diagnosis. Officials didn’t disclose what form of cancer Charles has but said it’s not related to his recent treatment for a benign prostate condition.

Officials have said the monarch is continuing with state business, including his regular weekly meetings with Prime Minister Rishi Sunak, and won’t be handing over his constitutional role as head of state.

It is not immediately known which other members of the royal family will attend Sunday’s service, but Prince William and Kate, the Princess of Wales, who announced last week that she is also undergoing cancer treatment, are not expected to attend.