02/12/2015 04:06 EST | Updated 04/14/2015 05:59 EDT

Newfoundland woman helps quantify risks of cancer that riddles her family tree

TORONTO - For Samantha Hansford, the research is personal.

A rare form of stomach cancer has slashed a swath through generations of her family, robbing her grandmother of seven siblings and a daughter.

That same grandmother has twice battled cancer. First was a type of breast cancer known to be linked to the stomach cancer gene that riddles the family tree of this Newfoundland clan. Then, as her 40-year-old daughter lay dying of stomach cancer, came a stomach cancer diagnosis of her own.

Hansford's own mother, who was also born with this deadly gene mutation, later had her stomach removed to avoid a cancer that seemed virtually inevitable.

New research Hansford and colleagues from the B.C. Cancer Agency published Thursday will actually help people who carry this gene mutation understand what their individual risks are of developing diffuse gastric cancer.

"There are different types of (research) papers," explains Dr. David Huntsman, who supervised Hansford and who earlier led the work that found the mutation on the CDH1 gene that so affects her family. Huntsman's team also developed the genetic test used to determine whether people carry this mutated gene.

"There are papers which have a whiz and a bang and then there are papers which are very, very useful and will influence care internationally immediately. And this is one of those (latter) papers."

Hansford, 26, and her co-authors analyzed the genetics of 75 families with a strong history of diffuse gastric cancer to calculate risks. There were earlier estimates based on 10 families, but having so much more data allowed the team to refine the calculations and feel more confident in the findings.

The work, published in the journal JAMA Oncology, reports that men who carry this CDH1 gene mutation have a 70 per cent chance of developing stomach cancer. For women, the risk is 56 per cent. And they also carry a 42 per cent risk of lobular breast cancer.

Huntsman said that form of breast cancer is generally responsive to treatment. And women of course can be screened for breast cancer; mammography allows for early detection and treatment.

But there is no way to screen for diffuse stomach cancer. Often by the time it is detected it is too far advanced to be cured. For these people, doctors like Huntsman recommend preventive surgery — removal of the stomach.

Hansford's mother, Geralyn, happily had the surgery in 2006. A few years earlier she lost her sister, Arleen, to stomach cancer, and she knew she carried the mutated gene.

She and a surviving sister went for genetic testing to see if they carried the gene mutation that has plagued her family. Her sister tested negative, but she drew the short straw.

"I want my stomach out," Geralyn Hansford, 55, remembers saying immediately upon hearing the news.

"I lived in fear from 1997" — when her sister was diagnosed — "right through until the day that I had my stomach removed. And after that time, I never think about it."

The research Samantha Hansford and her colleagues published also identified a number of other genetic mutations that may increase the risk of developing diffuse gastric cancer in people from families that don't carry this mutation but do have an elevated rate of these cancers. More work needs to be done to try to quantify the level of risk they pose.

The younger Hansford learned on her 18th birthday that she does not carry the mutated CDH1 gene. Neither does her only sister. They don't need to worry about the family disease, or about passing it on to any children they may have.

Her family's history propelled her into this work. "Losing my aunt in 2002, that's what really sparked my main interest in it," she said.

"But it wasn't until this genetic mutation was discovered in my family and in my mother and I had to go through genetic counselling that that kind of opened up my eyes to genetics and to this hereditary connection."

Geralyn Hansford is impressed and amazed at her younger daughter's work.

"It's mind-boggling that what she does can help people make decisions in their lives that will help them survive."