Study: Difficult-to-Detect Form of Breast Cancer Increasing

A difficult-to-detect form of breast cancer, which may be linked to use of combination hormone replacement therapy, is on the increase in the United States, according to a report in the Journal of the American Medical Association.

Researchers at the Fred Hutchinson Cancer Researcher Center in Seattle, analyzing records of 190,458 women who had breast cancer from 1987 through 1999 in nine areas ranging from the East Coast to Hawai, found the incidence of lobular breast cancer increased by more than 50 percent during this period.

Overall, lobular breast cancer, which forms in the milk-producing glands and is difficult to detect by mammogram or physical exam, accounted for 15.6 percent of breast cancers in 1999, the researchers reported.

The incidence of ductal breast cancer, which remains the most common form, remained esssentially unchanged during the study period, the researchers reported. Ductal breast cancer is easier to detect because it begins in the milk ducts and forms distinctive lumps.

The researchers noted that other research has suggested that use of combined estrogen and progestin hormone replacement therapy increases the risk of invasive lobular breast carcinoma, and said their study "adds to the evidence that there is an association between breast cancer and combination hormone replacement therapy (CHRT).

"Lobular breast cancer was increasing at the same time that CHRT was increasing," said researcher Dr. Christopher Li.

Other sources: Journal of the American Medical Association