The family of US pastor and author Tim Keller has urged people to pray for him, as he is “dealing with the side effects of an immunotherapy treatment” amid his ongoing battle with cancer.

In a Facebook post, Keller’s son Michael asked people to continue to pray for him and his medical team.

“We ask that you continue to pray for Dad’s healing--and for the decisions of his doctors and medical team who continue to provide excellent, compassionate care.

"Thank you for the outpouring of love and support.  

“We deeply covet your prayers at this time,” the post read.

Last month, Keller had told his social media followers he would be undergoing the treatment at the National Cancer Center in the US city of Mayland in June.

He said the treatment had shown “great promise in potentially curing cancer” but noted it was a “rigourous demanding month-long program” that would need updates, up to six months on.

Keller, who was diagnosed with stage four pancreatic cancer in 2020, also shared he and his wife Kathy would be “displaced from our home and separated from one another, as I will be an inpatient.”

At the time, he urged people to pray for “truly miraculous effects of the procedure and minimal side effects.”

The 71-year-old is also a survivor of thyroid cancer, which he suffered in 2002.