Mum-of-two Amaryllis Aitken is limbering up to lead Team Amy, made up of more than 70 women and girls, in tomorrow's race.
The following day, the 38-year-old will begin radiotherapy treatment for sarcoma.
The rare cancer was diagnosed in November last year, the day of Amaryllis' birthday.
She said: "I first noticed a lump on my leg, sort of walnut sized, after a box fit class and thought I had pulled a muscle.
"My GP thought the same, but said to go back if it didn't disappear. I went back six months later because it hadn't and, in November, sarcoma was diagnosed. It had also spread to my lungs. It was a very big shock, there is no history of cancer in my family."
Amaryllis, from Kibworth, had chemotherapy, followed by an operation to remove the sarcoma.
She said: "I feel fine at the moment, although I do get more tired than I used to. I told my close friends that I was going to do Race for Life and then I put it on Facebook and people just kept joining in. Now there are about 72 of us.
"Sunday is going to be fantastic. I am so proud of everyone for their support and help.
"When I booked a taxi through M & E Taxi, in Kibworth, I was told there wouldn't be a charge.
"It is an amazing and it is a very humbling experience."
Amaryllis's two daughters, Daisy 16 and three-year-old Scarlett, are among team members.
Team Amy is also hoping to raise £3,000 or more for Cancer Research UK, which organises the race.
Amaryllis said: "We have raised about £2,800, so I am sure we will get well over the £3,000 mark."
Also joining the team is one of her lifelong friends, Shora Montgomerie. Shora, a GP from Market Harborough, said: "I did the Race for Life a couple of years ago, but this year it seems that there is much more relevance to it.
"As a GP I have patients affected by cancer and, of course, know how important research is. But, Amy is the first of my friends and peer group to be directly affected by cancer.
"We have been friends since we were babies and we went to school together.
"When Amy shared her journey on Facebook so many friends from long ago saw it and wanted to be part of the team. There will be family and friends, children, mothers and grandmothers taking part and we will be walking the 5k route."