King Charles 'Is Positive' amid Cancer Treatment: His 'Doctors Are Optimistic,' Palace Source Says

King Charles, who revealed his cancer diagnosis on Feb. 5, is planning for a "summer diary"

King Charles is "positive" about his cancer treatment.

The King's team is said to be thinking about a summer schedule for the monarch, 75, amid "amplified confidence" in light of the sophisticated treatment he is receiving, a royal source tells PEOPLE.

The King is "progressing well" in his treatment, a source close to the royal household says. The royal source adds, "He is positive, the doctors are optimistic."

The source adds that King Charles has not been “operationally constrained" so far and Buckingham Palace is planning for “a summer diary.” However, his team won’t commit to any engagements and will rely on “medical advice nearer the time.”

The King's outings and engagements have been restricted to small numbers of people since the palace revealed his diagnosis on Feb. 5, However, towards the summer when the risk of airborne illnesses eases, more engagements could happen outside – such as Trooping the Colour, the annual public celebration of the monarch's birthday which will take place on June 15.

“There could be a slow increase of numbers of people they are able to meet indoors,” the source adds.

Related: Kate Middleton Had Private Lunch with King Charles Before Cancer Announcement: They Have a 'Very Good Bond'

A second source shared that King Charles' team is "planning as usual."

"One thing that has been wholly undiminished is his appetite for work," the royal source added.

In a positive sign, King Charles is set to attend the Easter church service on Sunday with Queen Camilla and members of the royal family. The traditional royal outing is expected to be smaller-scale than usual, following doctors' advice to limit the number of people King Charles should come in contact with during his treatment.

Last week, the monarch traveled to Buckingham Palace from Windsor Castle to meet with Korean War veterans to mark the 70th anniversary of the conflict. Late last month, the monarch also undertook his first face-to-face meeting with British Prime Minister Rishni Sunak since revealing his cancer news.

The King is also hoping to join the royal family's traditional Easter outing at St. George's Chapel at Windsor Castle on Sunday. However, the service will be on a smaller scale compared to previous years after doctors advised that King Charles should limit the number of people he comes into contact with during his treatment. His appearance won't be confirmed until the holiday.

Related: Kate Middleton, King Charles and Sarah Ferguson All Have Cancer in Unprecedented Royal Family Crisis

This comes as King Charles’ nephew Peter Phillips said his uncle is keen to get back to work following his diagnosis, which came after he received treatment for an enlarged prostate at The London Clinic on Jan 26.

Speaking to Sky News Australia in an interview that aired over the weekend, Peter, 46, shared that the King is in "good spirits" but is also "frustrated" at the limited amount of work he's able to do.

“I think, ultimately, he's hugely frustrated. He's frustrated that he can't get on and do everything that he wants to be able to do,” said Peter, who is the son of Princess Anne and her former husband, Captain Mark Phillips.

“But he is very pragmatic [and] he understands that there's a period of time that he really needs to focus on himself.”

“He is always pushing, his staff and everybody and his doctors and nurses to be able to say, 'Actually, can I do this? Can I do that?' " Peter continued. “So the overriding message would be that he's obviously very keen to get back to a form of normality."

“And he's probably frustrated that, recovery is taking a little longer than probably he would want it to," he added.

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Days before the interview aired, King Charles’ daughter-in-law Kate Middleton announced her own cancer diagnosis in an emotional video shared on social media Friday.

The Princess of Wales, 42, shared that she is currently undergoing chemotherapy after tests following her ”planned abdominal surgery” on Jan. 16 found “cancer had been present."

“I am now in the early stages of that treatment,” said Kate, adding that the news came as a “huge shock.”

A Buckingham Palace spokesperson said that King Charles is "so proud of Catherine for her courage in speaking as she did."

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