(CP) Two years after being diagnosed with stage 4 pancreatic cancer, Pastor Tim Keller, the founder of Redeemer Presbyterian Church and City to City, shared an update, saying, "God has seen it fit to give me more time," but "a rigorous and demanding" procedure awaits him.

The 71-year-old Christian author and speaker shared on social media Friday that this month, he's "celebrating the two-year anniversary of my diagnosis with pancreatic cancer," explaining that he can call it a "celebration with justification as the chemotherapies have reduced the stage 4 cancer that was found and God has seen it fit to give me more time."

However, Keller added, "we are also moving onto an immunotherapy trial at the National Cancer Center in Bethesda, Maryland, as of June 1. This has shown great promise in potentially curing cancer, though it is a rigorous and demanding month-long program (that will need updates up to six months)."

Requesting prayers for him and his family, the now-retired pastor further shared that his wife, Kathy, and he will be "displaced from our home and separated from one another, as I will be an inpatient."

He asked his followers to continue to pray "for truly miraculous effects of the procedure and minimal side effects."

Keller was diagnosed with cancer in May 2020.

In a health update he gave supporters last September, he wrote, "I was granted a 'chemo holiday' (missing one treatment) and was able to get out of town with my family for several weeks. On Aug. 23, I had a scan and the primary tumor had not progressed. However, a mystery lump underneath the May surgical scar was removed and proved to be cancerous."

"Pancreatic cancer is able to learn how to evade medication, so it is only God's power that we look to for complete healing," the author of Hope in Times of Fear said at the time.

"Please do pray that I will be able to fulfill my teaching and other obligations, and that the neuropathy and other side effects will be minimal while the medication will be effective against the cancer, and that we will run the race God has set before us with joy."

Keller is also a survivor of thyroid cancer, which he had in 2002.

In a previous interview with The Christian Post, Keller revealed he learned of his diagnosis while writing his book, which focuses on the transformative power of the resurrection.

"Here I am, writing a book about the resurrection, and I realized I only half-believed I was going to die. I went back and realized that in some ways, I also only half-believed in the resurrection — not intellectually so much, but all the way down deep in my heart. I realized I needed to have a greater, a deeper faith in the resurrection, both intellectually and mentally," he said.

Facing one's own mortality and spiritual reality, Keller told CP, drastically alters the way one looks at their time on Earth and magnifies the transformative power of the resurrection.

"The things of Earth become less crucial. They're not so important to you; you realize you don't need them to be happy. Once I believe that, I start to enjoy them more. I don't try to turn them into God; I don't try to turn them into Heaven, which is the only thing that can really satisfy my heart," he declared.

"You find that you have to really have a real spiritual experience of God's reality so that the things of this Earth 'grow strangely dim in the light of His glory and grace,'" Keller said, quoting the century-old hymn.

The pastor told CP that regardless of what happens, he was "ready for anything."

"What the future holds, I don't know. Pray that I would have years and not months left and that the chemotherapy would continue to be effective. But we are ready for whatever God decides for me. We're spiritually ready."

"I do know," he added, "that the resurrection of Jesus Christ really happened. And when I die, I will know that resurrection too."

© The Christian Post