Vince Flynn, the prolific and popular Twin Cities author of political thrillers, says that pain from treatment for his prostate cancer has gotten worse and forced him to push back release of his next novel until early next year.

Flynn, 45, said in a statement posted Tuesday on his website that the pain "made it nearly impossible to sit still and concentrate, which is a fairly important part of writing a book."

The Edina author of the series of best-selling novels centered on counter-terrorism fighter Mitch Rapp said his hope had been to "lock myself away at my cabin in June and July" to finish "Kill Shot" for a Christmastime release.

Now the release of his 13th book -- about Rapp's pursuit of those responsible for the Pan Am bombing over Lockerbie in 1988 -- is scheduled for Feb. 7, he said.

After about 20 radiation treatments "with very few side effects," Flynn wrote, "around September 1, fatigue began to set in. Once again, I found it extremely difficult to focus on the book for more than an hour or two."

He added that even though "my condition has continued to improve, my doctors have told me I will not be back to full strength until the first of November. After that, they say I will feel better than I've felt in two years."

Flynn's cancer was diagnosed in November 2010. At that time, he said that fighting the disease is "a battle I do not plan on losing."

Flynn's "Protect and Defend" and "Extreme Measures" became No. 1 New York Times bestsellers.

Paul Walsh • 612-673-4482