Unexplained Weight Loss Is Linked to Cancer

People who lose a significant amount of weight without dieting, exercise, or other lifestyle changes may also be at higher risk of some cancers, according to researchers who say a sudden drop may be an early indicator of the disease.

Those who spontaneously shed more than 10% of their body weight developed cancer at a rate of about 1,362 per 100,000 over a 12-month period, according to a study released Tuesday by the Journal of the American Medical Association, while the rate of diagnosis among people who hadn’t recently lost weight without explanation was 869 per 100,000.

While often seen as a positive step toward better health, a large drop in weight sometimes precedes a cancer diagnosis. Treating weight as an important vital sign may help doctors spot cancer earlier, when it’s more likely to be cured with available treatments.  

“Unexplained weight loss is where we say you should tell your doctor,” said Brian Wolpin, a medical oncologist at the Harvard-affiliated Dana-Farber Cancer Institute and co-senior author of the study. It’s hoped to “help primary care physicians have a better sense of the spectrum of cancers that may be present in someone who has this unintentional weight loss.” 

Tumors of the esophagus, stomach, and pancreas were among the most elevated among people who had recently shed pounds without trying. This may be related to trouble or pain swallowing, symptoms of upper GI cancers that can make it hard for patients to get adequate nutrition.

The researchers analyzed data from the Nurses’ Health Study, a research effort that began almost 50 years ago at Harvard, and the all-male Health Professionals Follow-Up Study that began in 1986. The studies looked at the weight of 157,474 participants every two years over an average of 28 years, while screening for all cancer types. 

The overall risk of being diagnosed with cancer remained low at 3.2% among those who had experienced significant weight loss compared to 1.3% who had not. Many types of cancer including breast, brain, and melanoma, had no significant associations with recent weight loss, the researchers found.

“Weight is something that should be measured well,” in doctors’ practices, said Michael Rosenthal, a doctor at Brigham and Women’s Hospital who helped write the study. “It should be a review of the weight as it has been charted over the last couple of years to see if there is a longitudinal decline that needs further evaluation.”