Routine breast self-examination can markedly improve a woman's chances of surviving at least five years after a diagnosis of breast cancer, according to the results of a study involving 248 women in Vermont.

The study revealed that women who examined their breasts monthly had about a 15 percent better five-year survival rate than women who never performed a breast self-examination, according to researchers at the University of Vermont and the Vermont Regional Cancer Center.

The researchers contacted the 339 women whose cancers were diagnosed at general hospitals in the state during a 23-month period. And 73 percent of the women agreed to participate in the study, and report whether, and how often, they had examined their breasts before the diagnosis of cancer.

According to Dr. Roger S. Foster Jr., who delivered a paper on the study at the American Society of Clinical Oncology's annual convention here last week, 26 percent of the women performed self-examinations monthly, 28 percent performed them less than once a month and 46 percent never examined their breasts for lumps.

There was a correlation between the ages of the women and their histories, with those in the 28-to 49-year-old range examining themselves every month, but only 7 percent of the women over 70 performing monthly exams.

There was also a link between the stage of cancer and the amount of self-examination, with 50 percent of those who performed self-examination monthly detecting their cancer while it was still in "stage one." Only 18 percent of those who never examined their breasts had their cancer detected at that stage.

On the other hand, only 5 percent of the self-examining group had stage three cancer, while 33 percent of those who didn't perform self-examination did not have their disease detected until it reached that advanced stage.

According to the study, 74 percent of the self-examination group survived at least five years after discovery of their disease, while only 59 percent, or 15 percent fewer, of the women who never performed self-examination survived that long.

According to specialists at the confercnce, the Vermont study should lend great impetus to campaigns to encourage women to perform monthly self-examinations.

Foster called for programs to teach women to examine themselves and then follow their medical histories, comparing them to women in far more expensive, involved programs of screening by physicians and mammography.