Two courses of chemotherapy have not stopped the convulsions, which began in 2010 - five years after surgery to remove one-third of the tumour.
The radiotherapy, which Fairlie will receive as an outpatient at the Beatson Oncology Centre in Glasgow, is intended to shrink the remaining growth, and a further course of chemotherapy will resume thereafter.
In an interview in today's Herald Magazine, the 49-year-old, whose eponymous restaurant at the Gleneagles Hotel in Perthshire is the only one in Scotland to have two Michelin stars, speaks frankly about how he is living with his condition while continuing to run the 50-cover restaurant, which has been voted the best place to eat in the UK and is currently 17th in the list of the world's top 100.
He describes how the seizures can last anything from 10 to 45 seconds and mainly affect his left arm. Chemo- therapy, which he takes in tablet form at home, leaves him feeling exhausted and nauseous.
But he says: "I am very lucky in that the type of tumour I have responds to treatment, and I can continue to have chemo. I cycle to keep fit, as I have always done. At the clinic I have seen others who aren't so lucky.
"I feel very optimistic that research into brain tumours is ongoing."