During an average follow-up of over five years, invasive breast cancer was diagnosed in 4% of women with ductal carcinoma in situ (DCIS) and 6.2% of women with lobular carcinoma in situ (LCIS). Among with women with DCIS, risk of subsequently being diagnosed with advanced breast cancer was higher among Black women and Hispanic White women than among non-Hispanic White women. These results were published in the journal Cancer.
DCIS and LCIS are conditions in which abnormal cells are found in the ducts or lobules of the breast. DCIS is often detected by screening mammography, and LCIS is most often an incidental finding on a breast biopsy done for another reason. DCIS is thought to be a direct precursor of invasive breast cancer, is highly curable, and its removal prevents invasive breast cancer. LCIS is thought to be an indicator for an increased risk of developing invasive breast cancer, but may not be the direct precursor abnormality. The role of early treatment is less clear for patients with LCIS.
Although the rates of DCIS and LCIS have increased in recent years, due at least in part to an increase in the number of mammograms and breast biopsies, there is little information about which women with the conditions are most likely to go on to develop invasive breast cancer.
To explore the frequency, types, and predictors of invasive breast cancer after a diagnosis of DCIS or LCIS, researchers evaluated information from a large U.S. cancer registry.
The study included 37,692 women with DCIS and 4,490 women with LCIS. All women had been diagnosed between 1988 and 2002. Because a majority of women with LCIS who had been treated with a mastectomy had undergone a bilateral mastectomy (removal of both breasts), LCIS patients treated with mastectomy were excluded from the study. This exclusion criterion was not applied to DCIS patients because most DCIS patients treated with mastectomy had a unilateral mastectomy (removal of one breast).
- 1,504 of the 37,692 DCIS patients (4%) were diagnosed with invasive breast cancer during an average of five and a half years of follow-up.
- 282 of the 4,490 LCIS patients (6.2%) were diagnosed with invasive breast cancer. These cancers were more likely to develop in the same breast as the LCIS than in the opposite breast. This finding contradicts some previous studies, which have suggested that cancer after LCIS occurs as frequently in the opposite breast as in the same breast.
- Compared to DCIS patients, LCIS patients were less likely to be diagnosed with invasive ductal carcinoma and more likely to be diagnosed with invasive lobular carcinoma.
- Among the DCIS patients, Black women had a higher risk of subsequent invasive cancer than non-Hispanic White women. Risk of being diagnosed with more advanced breast cancer (stages III or IV) was higher among young women (those 20-49 years of age), Black women, and Hispanic White women.
Based on these results, the researchers suggest that young DCIS patients may benefit from more frequent screening, and that better follow-up of Black and Hispanic women may reduce their risk of late-stage cancer. The researchers also suggest that rather than simply being a marker of increased breast cancer risk, LCIS may be a cancer precursor.
Reference: Li CI, Malone KE, Saltzman BS et al. Risk of Invasive Breast Carcinoma Among Women Diagnosed with Ductal Carcinoma in Situ and Lobular Carcinoma in Situ, 1988-2001. Cancer. 2006;106:2104-2112.
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