His mum, aunt and gran all found they had the disease a few years ago – and his gran sadly died.
Marc, 42, had never been much of an athlete – but he decided he wanted to do “something big” in their honour.
So he has been in training and is now entering a total of 20 events as part of a year-long challenge which will see him run 600 miles by the end of December – the equivalent of running a marathon every fortnight.
The Capital-based EE store manager has been taking part in obstacle courses, endurance events and marathons to raise money for Macmillan Cancer Support.
And he has also benefited personally by losing more than four stone in weight.
He said: “Before this I wasn’t very fit but now I have got a total taste for it.
“I started off the year at 18 stone. I am now under 14 stone.”
But he admits it has been a demanding time. “The first event was the hardest one I have done in my life. I was a broken man – I couldn’t walk for two days.”
He has already completed three endurance races, ten obstacle course races, two full marathons and one half marathon.
Marc’s next challenge is the Men’s 10K event in Edinburgh this weekend .
He said: “Everyone thinks I’m crazy but they have been very supportive.
“Cancer has impacted three close family members – my mum, auntie and my gran, who unfortunately died. Macmillan helped my family in so many ways. These runs are all in their honour, and for every other person out there who has been affected.”
Marc’s mother Sandie was the first of his relatives to be diagnosed with breast cancer. Just after she had her operation, her mother-in-law was diagnosed and then her brother’s wife.
Sandie, 62, who now lives in Spean Bridge, near Fort William, said: “We have had quite a time but we’ve had great support from Macmillan throughout the family. When Marc decided he was going to do these races, I said I thought he was a bit old for it, but he’s thoroughly enjoying himself.
“I’m very proud of him, I must admit. He’s doing really well.”
Marc has set up a JustGiving page at: http://www.justgiving.com/Marc-Cherrie4
He says there that: “2015 is my year to help raise as much money as possible for Macmillan.”
The Men’s 10K starts from the Lawnmarket on Sunday at 10am, finishing at Murrayfield stadium.
The event, which was started a decade ago by the Men’s Health Forum Scotland, is deliberately promoted to attract men who are new to physical activity or have been inactive for a while and every year consistently includes around 40 per cent of those taking part who have never entered a running event before.