A study by Blue Cross-Blue Shield seems to support fears that many surgical operations are performed needlessly.

Among 1,500 cases where elective (non-emergency) surgery was recommended and a second opinion was sought, in one of every four cases the first doctor's recommendation was not upheld.

The findings are not necessarily conclusive, cautioned D. Eugene Silbery, executive vice president of the Blue Cross-Blue Shield plan of Greater New York.

"We are continuing to study the patients to add further data to see how many had operations immediately anyway, how many deferred them for a year or two, or perhaps indefinitely," Silbery said. "We also want to see what happens to the people who have decided not to have surgery.

"However, we believe the program is immediately beneficial if some subscribers are spared pain by not having surgery. In terms of lowering costs, we also anticipate significant savings." For each operation not performed, he said, the insurance plan saves about $1,500 in hospital fees.

In 1976, a congressional subcommittee concluded that unnecessary surgery was costing $4 billion annually. Last fall Health, Education and Welfare Secretary Joseph A. Califano Jr. announced the government would begin paying for second opinions for Medicare patients.