Preacher and bestselling author Tim Keller has said the cancer in his body has not grown and that he is praying for it to decrease. 

Keller, 70, posted an update on Twitter on Sunday, saying the news was "extremely encouraging" and that the cancer had remained unchanged for nine months. 

The former pastor of Redeemer Church in New York was diagnosed with pancreatic cancer last year when he was in hospital for something else and it was found, something he called "providential intervention".

He asked for people's prayers at the time for minimal side effects so that he could "continue writing and speaking" while he underwent treatment.

Keller, who wrote The Reason for God, was also diagnosed with thyroid cancer back in 2002 and wrote about the experience in his 2013 book, "Walking with God through Pain and Suffering." 

He stepped back from leading Redeemer Church in 2017 but continued to preach and write. 

He said in a recent video that his greatest fear was not dying from cancer but getting a positive test result and going back spiritually to where he was before the diagnosis, saying it has taught him to rely on God much more.