Tim Keller is asking people to pray that his cancer treatment will be effective and that he and his wife Kathy will stay the course.
The pastor and author has been battling stage 4 pancreatic cancer since May 2020.
In an update on Facebook, Keller said he had been granted a "chemo holiday" after successful surgery in May, and that he had been able to spend a few weeks with his family outside of New York.
On August 23, a scan showed that the primary tumor had not progressed but it also revealed a "mystery lump" under the surgery scarring.
This lump proved to be cancerous and has now been removed.
As a precaution, his chemotherapy has been scaled up to the same level as before his May surgery.
The 70-year-old, who previously beat thyroid cancer in 2002, is asking for prayer as he grapples with "treatment, isolation and covid."
"Pancreatic cancer is able to learn how to evade medication, so it is only God's power that we look to for complete healing," he said.
"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."