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19 August 2005
Better Results From Mammography Detection 
A new study in the Journal of the National Cancer Institute has found that women whose breast cancer was detected by screening mammography had a significantly better prognosis than those whose cancer was found another way - even if the cancer had already spread to their lymph nodes. The researchers believe a likely reason for the finding is that mammography can detect tumors that are both slower growing and less biologically lethal than those found symptomatically. The study's lead author, Donald Berry, said that the results are important because the survival benefit seen in this analysis is much greater than one would expect for screen-detected breast cancer. Conducted at The University of Texas M. D. Anderson Cancer Center, the researchers looked at outcomes from randomized screening studies of more than 150,000 women. "We know that screening picks up many tumors before they can be detected in other ways and women may benefit from early treatment, but the advantage we found is much larger than what would be expected from the so-called stage shift that is associated with screening mammography," Berry said. "The important message here for clinicians and patients is that breast cancer detected through mammography has a substantially better survival prognosis. Of two women who have the same age, size of tumors, and similar stage of cancer and spread to lymph nodes, the one whose cancer was detected with mammography has a reason to be happier than the woman whose cancer was detected symptomatically." But Berry said the conclusion should not be over interpreted. "The paradox is that this result does not mean screening is beneficial," he noted. "Without screening, some of the women would not have been diagnosed with breast cancer at all, and in that group, some of them could have avoided surgery and treatment without detriment. The rub is that we don't know which ones they are." This issue has long plagued screening mammography, especially when the detected tumors are very small and have not spread. But this study appears to add a new element to the debate. "Our conclusions apply generally, and are as important in node-negative breast cancer as they are in node-positive disease," Berry said. All things being equal, the method of detection was a statistically significant independent predictor of breast cancer survival. After adjusting for stage of disease, patients whose breast tumors were discovered after a previous negative mammography screen had a 53 percent greater risk of death from the cancer than women with screen-detected cancer. Patients in the control group (where no mammography was used) had a 36 percent increased risk of death compared to screened patients. "What is new here is that we found an effect that is beyond stage shift," Berry said. "All breast oncologists know that tumors detected by mammography have a better survival than tumors detected otherwise because they are smaller and more likely to be node-negative. Our study shows that these patients are even better off than their clinical characteristics suggest."
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