Compared to stomach cancer in older adults, this new, early onset form often grows and spreads more quickly, has a worse prognosis, and is more resistant to traditional chemotherapy treatments, said the study published in the journal Surgery.
While rates of stomach cancer in older patients have been declining for decades, this early onset of cancer is increasing and now makes up more than 30 per cent of stomach cancer diagnoses.
"I think this is an alarming trend, as stomach cancer is a devastating disease," said senior author Travis Grotz, a surgical oncologist at Mayo Clinic in the US.
The research team studied 75,225 cases using several cancer databases to review stomach cancer statistics from 1973 to 2015.
Today, the average age of someone diagnosed with stomach cancer is 68, but people in their 30s, 40s and 50s are more at risk than they used to be.
"Typically, we see stomach cancer being diagnosed in patients in their 70s, but increasingly we are seeing 30- to 50-year-old patients being diagnosed," Grotz said.
The increased rate of the early onset disease is not from earlier detection or screening, Grotz added.
"There is no universal screening for stomach cancer, and the younger patients actually presented with later-stage disease than the older patients," he said.
In addition to being more deadly, early onset stomach cancer is also genetically and molecularly distinct, researchers found.
Furthermore, traditional risk factors for developing stomach cancer among older people, such as smoking tobacco, did not appear to correlate with its early onset counterpart.
"Hopefully, studies like this will raise awareness and increase physician suspicion of stomach cancer, particularly in younger patients," Grotz said.
Younger patients who feel full before finishing a meal, or have reflux, abdominal pain, unintentional weight loss and difficulty eating should see their health care provider, he added.
( With inputs from IANS )