CHICAGO -- A large study of Japanese adults found those with diabetes were more likely to develop cancer, especially of certain organs such as the pancreas and liver, researchers said on Monday.

Men with diabetes in the study of nearly 98,000 people were 27 percent more likely than non-diabetics to be diagnosed with cancer, the study by the National Cancer Center in Tokyo found. Women afflicted with diabetes were also more at risk for cancer, though the association was not as clear as with men.

Study author Manami Inoue wrote in this month's Archives of Internal Medicine that researchers have suspected a link between the two diseases but have not had conclusive evidence.

One theory holds that adult-onset diabetes produces excess insulin that may promote cancer cell growth in the liver or pancreas.

Diabetes -- which is on the rise in many parts of the world - may also alter levels of sex hormones that could contribute to ovarian cancer in women and prostate cancer in men.

But Inoue cautioned that either disease may be the cause of the other, and both may be tied to obesity in many patients.

Also, diabetic patients pay more visits to the doctor and the increased vigilance may result in more cancer diagnoses, the study said.