A study in the research journal Cancer concludes that early stage, localized breast cancer puts women at a higher risk of developing invasive breast cancer than previously thought.

The new work looked at the differences in outcomes for women with two different types of abnormal breast tissue: ductal carcinoma in situ (DCIS) and lobular carcinoma in situ (LCIS).

DCIS is the most common form of early breast cancer and is usually found during a mammogram. By definition, DCIS is limited to the milk ducts where it originated. But doctors have long considered DCIS a possible precursor to more advanced stages of cancer and so it is usually surgically removed.

LCIS, by contrast, develops and remains in the milk-producing glands. LCIS is usually found by chance during a breast biopsy and has previously been considered a risk factor for invasive breast cancer but has not been thought to be necessarily a precursor and so it is often monitored and treated surgically only if changes occur.

Researchers from the Fred Hutchinson Cancer Research Center looked at medical records dating between 1998 and 2002 from 11 cancer registries to see how invasive breast cancer was diagnosed among 37,692 DCIS patients and 4,490 LCIS patients. They found that women with LCIS were 5.3 times more likely than those with DCIS to develop invasive cancers in the milk glands. LCIS raised the risk of invasive breast cancer for a woman in the general population by four-fold. Women with DCIS had as much as an eight-fold increased risk of developing invasive breast cancer compared with women in the general population.

Hispanic and African-American women as well as women under 50 were at greater risk of advanced stage breast cancer if they had DCIS, when compared with Caucasian and older women.

What It Means: Doctors are now rethinking risk, treatment and follow-up for DCIS and LCIS. More frequent screening of younger women with DCIS and better, more thorough follow-up with Hispanic and African-American women with DCIS might reduce the incidence of advanced stage breast cancer. Due to the higher rate of invasive cancer in the glands for LCIS patients, as well as a higher rate of cancer recurring in the same breast, the researchers also suggest that doctors might want to consider earlier, localized treatment of LCIS. 

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