London, UK - Sources close to the royal family have confirmed that Kate Middleton has "turned a corner" and is making positive strides in her cancer treatment.

"It has been a great relief that she is tolerating the medication and is actually doing a lot better," a family friend told Vanity Fair in an update shared Tuesday.

The 42-year-old is currently undergoing preventative chemotherapy for an undisclosed form of cancer.

The treatment has been a "very challenging and worrying time" for Kate, the insider added.

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Amid her recovery, Kate was recently spotted out and about with her family, sparking speculation about when the Princess of Wales will return to official appointments.

Reports that the mother of three is not expected to return to work until next year are not true, Vanity Fair writes, but there is still no timeline for Kate's comeback.

"There is no timeline, and there is certainly no hurry. It will be when Catherine feels ready and when she gets the green light from her medical team," a source said.

"But she will 100% be coming back to work, of that there is no question."

Until then, Kate still urgently needs her privacy as she continues to recover.

While her husband, Prince William, has returned to royal duties, Kate has not made an official appearance since Christmas, stepping out of the limelight as she underwent abdominal surgery in January before disclosing her cancer diagnosis in March.