Over the last few decades, as breast cancer has increasingly been treated as a systemic disease, the number of surgeries performed in the most serious cases has plummeted. With better drugs and radiation techniques available, the proportion of women with stage 4 breast cancer who had surgery dropped from 67.8 percent in 1988 to 25.1 percent in 2011, according to a study published Wednesday in the journal JAMA Surgery.

But the study raises an intriguing question about that approach. It shows that women who had surgery survived longer than those who didn't: a median of 28 months vs. 19 months. When the researchers examined a small subset of the group - those who survived 10 years - they found 9.6 percent had chosen to have surgery and 2.9 percent had not.

"Maybe we need to revisit this question of surgery," said Mary C. Schroeder, an assistant professor in the College of Pharmacy at the University of Iowa and one of the authors of the study. "It may not be right for all women, but it may be better for some women than it was in 1995."

Previous research had reached the same conclusion, but a significant problem with this study and others like it is that they rely on retrospective data, looking back over any number of years, said Michael S. Sabel, chief of surgical oncology at the University of Michigan, who was not involved in the newly published study. In retrospective research, it's impossible to filter out the countless reasons a woman and her doctor might have made the decision to treat the cancer with or without surgery, leaving the conclusions unreliable for clinical decision-making, he said.

"It's premature to suggest, and it's a difficult conversation to have with patients, that removing the breast will help them live longer in the face of stage 4 disease," Sabel said.

Two small prospective studies have suggested no survival difference among women with stage 4 breast cancer who have surgery and those who don't, he said. A large, randomized, prospective study being conducted by the Eastern Clinical Oncology Group should produce the most reliable data on the subject to date, he said.

In stage 4 cases, cancer cells have left the breast, metastasizing to bones or other organs, which presents a more dire and immediate threat to patients' survival than the presence of the original tumor. Still, there may be reasons to remove the cancer in the breast. Some evidence suggests it may be influencing the woman's immunological response to her cancer. Or it could be continuously "seeding" the spread of cancer to other parts of the body.

In their study, Schroeder; Alexandra Thomas, a professor at Iowa's Carver College of Medicine; and others looked at 21,372 women from 1988 to 2011 who had stage 4 breast cancer at the time of their original diagnoses who did not receive radiation as part of their first course of therapy. Their median age was 63.

The researchers found median survival for all of the women improved from 20 to 26 months as more sophisticated treatments and better imaging techniques developed over that time. As other research has shown, African American women were overrepresented among women who have stage 4 breast cancer at the time they are first diagnosed.

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