The new study “is a big deal and has been the buzz of the breast cancer research world,” said Dr. Larry Norton of Memorial Sloan Kettering Cancer Center in an email. He was not involved in the study, although he said he had done paid consulting work for the past two years for the maker of Abraxane.

Beyond changing treatment practices, he said the research “opens the door to new approaches to harness the immune system to fight breast cancer, and there is every reason to expect major advances there.”

He cautioned that the combined treatment would have to be studied further, to assess side effects.

Dr. Kevin Kalinsky, a breast cancer specialist at NewYork-Presbyterian/Columbia University Irving Medical Center, suggested that patients like those in the study should talk to their doctors “about whether it is possible for them to get access to the medication while we’re waiting for F.D.A. approval.”

He did not take part in this study. He said he has received consulting fees from about 10 drug companies, including Genentech.

The women in the study had triple-negative breast cancer that had been newly diagnosed and had become metastatic, meaning it had begun to spread. Once that occurs, the outlook is grim, with many patients surviving 18 months or less.

Half received chemo alone, and half were given chemo plus immunotherapy.

Among those who received the combination, the median survival was 21.3 months, compared with 17.6 months for those who received chemo alone. The difference was not statistically significant.