James and Isaia Piho, Karyn Paringatai and Tania Aimers had their stomachs removed after they tested positive for the gene CDH1, which runs through their extended family.
They will join a group of about 80 people taking part in the Moro Marathon in Dunedin to support and raise awareness of the work of University of Otago's Centre for Translational Cancer Research.
Among other work, a group of scientists at the centre is researching an alternative way to prevent this specific cancer forming.
The researchers, in conjunction with clinicians, are focusing on the development of a pill that could be taken daily to chemically stop the gene process that causes the cancer.
Researcher Tanis Godwin said the centre was trying to raise awareness of its work and, through sponsorship for events like the marathon, hoped to raise cash to fund the sort of research "we think is important", as government funding was often targeted for other things.
Ms Paringatai, an Otago University lecturer, said all of her family would benefit from any successful research.
Paringatai family members had a 50% chance of inheriting the gene CDH1 and, if it was inherited, there was about an 80% chance of developing an aggressive cancer under the stomach lining. For anyone with the gene, the only certain way of preventing cancer, as yet, was to remove the stomach.
The surgery was publicly funded.
She and about a dozen members of her extended family had had their stomachs removed since her aunt learned a few years ago that the gene could be identified in testing.
"None of us wanted to live in fear that every time we had a sore stomach, or were throwing up from something, that it was stomach cancer. It was such high odds, and we have families. It was just too high a risk."
James Piho, a drug and alcohol counsellor, and his brother, Isaia, a firefighter, had their stomachs removed in May.
Their mother died from stomach cancer.
Isaia, who had already had cancerous cells present, said he would rather not have had the life-changing operation, but wanted to have children in the future and thought it would be nice if he was around for them.
"If there was an alternative, I would have had it."
Their cousin, Tania Aimers, a volunteer, said she, too, had her stomach removed for the sake of her family.
She also supported the research centre because, from next year, her daughter would have to be monitored regularly for the cancer. She wanted to make sure the research continued.
Food James Piho, Mrs Aimers and Ms Paringatai consumed now went directly to their small intestine, where it was processed and passed on through the bowel, while Isaia Piho had had a pouch inserted to replace his stomach.
Not having a stomach had been difficult, Ms Paringatai said. Hers was taken out two years ago.
The natural hunger triggers were gone and eating had to be done by the clock.
Food could not be consumed in the same amounts and it often came back up.
"The first six months was quite hard."
It did not affect her ability to run. She just had to make sure she had eaten beforehand and drank plenty of fluids.
She ran a half-marathon last year.
The three others were still deciding whether to walk or run, as their surgery was done only in the last few months.
