Most women diagnosed with breast cancer in the United States are operated on by surgeons who perform relatively few of these operations each year, according to a U.S. study released on Monday.

The finding by researchers in Wisconsin is startling in light of recent U.S. and U.K. studies that showed women had a better chance of surviving breast cancer if operated on by a surgeon who did at least 15 to 30 of the operations each year.

Only 10 percent of women with the disease go under the knife of someone who meets the higher end of that range, according to an analysis of Medicare data from 1994-1995 by the Medical College of Wisconsin in Milwaukee.

Almost half of the 8,105 women in the study were cared for by surgeons who did 12 or fewer breast cancer operations in the two-year period. Twenty-eight percent of surgeons had performed no such operations on Medicare patients in each those years.

The findings were published in the Aug. 9 online edition of the American Cancer Society’s journal Cancer.

“I’m amazed that there are surgeons out there who are doing just a handful a year and still doing them,” said Dr. Herman Kattlove, a medical oncologist with the American Cancer Society in Los Angeles, California.

“It worries me because if you’re not doing many of them, you’re not really going to keep up with the latest information,” Kattlove said.

He added that the tendency of some primary care physicians to refer breast cancer patients to one known specialist, especially in rural areas, might help explain why so many surgeons were not doing these operations more frequently.

Unlike pancreatic cancer and other types of cancer, breast cancer is common in the United States.

An estimated 200,000 women are diagnosed with the disease each year, with most undergoing surgery as part of their treatment. Although survival rates have improved in the past decade, more than 40,000 die from breast cancer annually.