Sam Shapiro, 85, a Johns Hopkins University professor whose pioneering research demonstrated that mammograms can reduce women's mortality from breast cancer, died of cancer Dec. 30 at his home in North Baltimore.

In the 1960s, Mr. Shapiro was director of research at a health maintenance organization, the Health Insurance Plan of Greater New York, when he became interested in the application of mammography for screening women and reducing mortality from breast cancer.

At the time, mammography was little used and its effect little known, and HMOs were not common.

Mr. Shapiro initiated a study that would ultimately change medical thinking about cancer. By the 1970s, after he had published his widely heralded work, mammography had become commonly used to diagnose and treat breast cancer at an early stage.

As a researcher in public health policy, he studied the effectiveness of medical treatments in large populations. Though trained as a mathematician, he became a nationally known biostatistician and epidemiologist.

In 1988, Mr. Shapiro became the first nonphysician to receive the Charles E. Kettering-General Motors Cancer Research Foundation Prize, a top medical honor. The judges lauded his research that "almost unilaterally changed medical thinking about early detection" of breast cancer.

Mr. Shapiro, a New York native, was a 1933 mathematics graduate of Brooklyn College. He did graduate work in mathematics at Columbia and George Washington universities.

He joined Johns Hopkins in 1973 as director of its health services research and development center in its Public Health School. In 1992, he was named acting chairman of the university's Health Policy and Management Department. Although he formally retired in 1998, he continued to work at the university in 1999.

He was the author or co-author of more than 200 scientific works. He had been elected to the Institute of Medicine and the National Academy of Sciences.

Survivors include his wife, the former Sema Deitch, whom he married in 1938; two children; two grandchildren; and two great-grandsons.