A diagnosis of pancreatic cancer usually carries with it a poor prognosis, and the news may be even worse for those who are obese: It could mean dying two to three months sooner than pancreatic cancer patients of normal weight, new research shows.
Previous studies have tied obesity to a higher chance of getting pancreatic cancer, but the new study asked whether the disease affects the tumour's aggressiveness and the patient's overall survival.
"[The new research] adds to the growing body of evidence that obesity is linked to cancer," said Dr Smitha Krishnamurthi, an associate professor of medicine at the Case Western Reserve University School of Medicine in Cleveland in the American state of Ohio.
The study was published in the Journal of Clinical Oncology.
Krishnamurthi was not involved in the new study, but wrote a commentary after seeing the study.
Pancreatic cancer remains one of the most deadly tumour types as it is so often asymptomatic and detected late.
The American Cancer Society says more than 45 000 people will be diagnosed with the disease this year and it will claim over 38 000 lives.
In the new study, a team led by Dr Brian Wolpin, an assistant professor of medicine at the Dana-Farber Cancer Institute and Harvard Medical School, collected data on more than 900 patients with pancreatic cancer who took part in either the Nurses' Health Study or the Health Professionals Follow-Up Study. These patients were diagnosed during a 24-year period.
After diagnosis, the patients lived for an average of only five months. Normal weight patients, however, lived two to three months longer than obese patients, the researchers found, taking into account factors such as age, sex, race, ethnicity, smoking and the stage of the cancer at diagnosis.
The study did not, however, prove a cause-and-effect relationship between weight and length of survival.
In addition, obese patients were more likely to have more advanced cancer at the time they were diagnosed compared with normal-weight patients.
Overall, the cancer had already showed signs of spreading in 72% of obese patients at the time of diagnosis, compared with 59% of normal weight patients.
It also seemed to matter how long the patient had been obese. The association between weight and survival was strongest for the 202 patients who were obese 18 to 20 years before being diagnosed with pancreatic cancer.
Krishnamurthi said the reasons for the link aren't clear.
She said the study can't tell whether shorter survival in obese patients "was due to biological changes that can occur in obesity, such as increased inflammation in the body, or whether the obesity caused other conditions that interfered with the treatment of pancreatic cancer.
"We need more research into how obesity may increase cancer rates and/or aggressiveness," she said.
Wolpin said the research "reinforces the importance of maintaining a healthy weight throughout life, which may lead to better outcomes after diagnosis and help prevent pancreatic cancer from developing.
"While our findings will not affect the way we treat patients today, they provide new leads for investigating the molecular pathways that may be responsible for the survival difference between obese and healthy weight patients," Wolpin said.
"Hopefully, in future, research will bring new approaches for treatment of pancreatic cancer."
Another expert agreed.
"This finding may provide clues about the biology of pancreatic cancer that could eventually be useful in treating patients," said Eric Jacobs, strategic director of pharmaco-epidemiology at the American Cancer Society.
"At this point, however, the great majority of pancreatic cancer patients, regardless of their weight, will die of their disease within a few years," Jacobs said.
"The most important thing to know about obesity and pancreatic cancer is that maintaining a healthy weight throughout life can help lower the risk of ever developing this highly fatal cancer."
For more information on pancreatic cancer, visit the American Cancer Society.