A standard treatment for localised prostate cancer is to remove the whole gland, a procedure called radical prostatectomy, but this fails to stop the cancer in nearly a third of patients.
Japanese researchers looked at 555 men who had had radical prostatectomy, examining their case 52 months on average after the operation.
Patients with blood group O were 35 percent less likely to have a recurrence of cancer compared with patients with blood group A, they found.
"This is the first time that anyone has shown that prostate cancer recurrence can vary with blood group," Yoshio Ohno of Tokyo Medical University said in a press release.
More work is needed to explore this surprising finding, but if the results are confirmed, important changes lie in store for medical practice, he said.
"For example, should we be counselling people with certain blood groups that they have a greater or lesser chance of recurrence, and should these risk factors be built into decisions on treatment?"
The research was issued at a conference in Stockholm of the European Association of Urology.