According to a study published in the Journal of the National Cancer Institute, breast cancers detected by screening mammography have a better prognosis than breast cancers detected because of symptoms, even after accounting for the stage of the breast cancer at diagnosis.
Breast cancer is diagnosed in approximately 250,000 women annually in the United States alone. The disease is highly curable when it is found and treated early. Several previous clinical trials of screening mammography have reported that mammography detects breast cancer earlier and improves overall survival in breast cancer patients. However, there’s less information about whether screen-detected cancers have a better prognosis when compared to non-screen-detected cancers of a similar stage.
To address the question of whether breast cancer detected by screening mammography has a better prognosis than breast cancer detected because of symptoms, even after accounting for stage of breast cancer at diagnosis, researchers analyzed data from three large clinical trials of breast cancer screening. One trial was conducted in New York, and the other two were conducted in Canada. Together, the three trials enrolled a total of over 150,000 women. The researchers report that among women of a similar age and with the same stage of cancer at diagnosis, women with screen-detected breast cancer were less likely to die of breast cancer than women whose cancer was detected because of symptoms. These findings are similar to those of a 2004 Finnish study, which also found that method of breast cancer detection was an important predictor of prognosis.
The researchers conclude that breast cancer detected by screening has a better prognosis than breast cancer of a similar stage that is detected because of symptoms. This information may help physicians refine estimates of a patient’s expected survival time after a breast cancer diagnosis, as well as augment support in favor of screening mammography.
Reference: Shen Y, Yang Y, Inoue LYT et al. Role of detection method in predicting breast cancer survival: analysis of randomized screening trials. Journal of the National Cancer Institute. 2005;97:1195-1203.
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