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How Much Does LCIS Diagnosis Increase Risk of Breast Cancer?

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LCIS (lobular carcinoma in situ) is a collection of abnormal cells growing in the lobules, the milk-producing glands at the end of breast ducts. In LCIS, the abnormal growth remains inside the lobule and doesn’t spread to surrounding tissues. People diagnosed with LCIS tend to have more than one lobule affected.

Most LCIS is hormone-receptor-positive, meaning that estrogen and/or progesterone fuel the growth of the abnormal cells.

Even though its name includes the word “carcinoma,” LCIS isn’t invasive disease. For this reason, some experts prefer using the term “lobular neoplasia” instead of “lobular carcinoma.” A neoplasia is a collection of abnormal cells.

LCIS is considered uncommon, but it’s not clear how many people are affected. That’s because LCIS doesn’t cause symptoms and usually doesn’t show up on a mammogram. It tends to be diagnosed because a breast biopsy was performed for another reason.

We know that LCIS increases the risk of being diagnosed with breast cancer in the future. Still, doctors haven’t been sure how much LCIS increases breast cancer risk.

A study suggests that breast cancer risk goes up about 2% per year in the first 6 years after a LCIS diagnosis. The study also found that women who took preventive hormonal therapy after an LCIS diagnosis were less likely to be diagnosed with breast cancer.

The study was published online on Sept. 14, 2015 by the Journal of Clinical Oncology. Read the abstract of “Lobular Carcinoma in Situ: A 29-Year Longitudinal Experience Evaluating Clinicopathologic Features and Breast Cancer Risk.”

The study included 1,060 women diagnosed with LCIS at the Memorial Sloan Kettering Cancer Center between 1980 and 2009. None of the women had been diagnosed with breast cancer when they were diagnosed with LCIS. The researchers looked at the women’s medical records to compare their treatments, as well as how many women were later diagnosed with breast cancer.

More than 98% of the women (1,043) were diagnosed with LCIS after 1990. Age at LCIS diagnosis ranged from 27 to 83 years.

Most of the women opted for careful observation as treatment. This means that the women followed a schedule of breast exams and screening to detect any signs of breast cancer as soon as possible:

  • 78% (831 women) chose careful observation
  • 17% (173 women) chose careful observation but also decided to take preventive hormonal therapy medicine
  • 5% (56 women) chose to have a preventive double mastectomy (two of the women taking preventive hormonal therapy medicine later had a preventive double mastectomy)

The researchers found that 150 women who were being carefully observed developed 168 breast cancers -- 18 women developed breast cancer in both breasts. About 2% of the women developed breast cancer each year in the first 6 years after being diagnosed with LCIS.

Among the women diagnosed with breast cancer:

  • 94 women developed cancer in the same breast that had LCIS
  • 38 women developed cancer in the opposite breast
  • 18 developed cancer in both breasts
  • 109 (65%) of the cancers were invasive -- 85% of these cancers were hormone-receptor-positive
  • 59 (35%) of the cancers were DCIS

Compared to the women who were only carefully monitored, women who were carefully monitored and took preventive hormonal therapy were much less likely to develop breast cancer:

  • after 5 years of follow-up, 3% of the women who took preventive hormonal therapy had developed breast cancer compared to 7% of women who were only carefully monitored
  • after 10 years of follow-up, 12% of the women who took preventive hormonal therapy had developed breast cancer compared to 21% of the women who were only carefully monitored

This difference was statistically significant, which means that it was likely because of the preventive hormonal therapy and not just due to chance.

The following factors didn’t seem to affect a woman’s risk of developing breast cancer after an LCIS diagnosis:

  • age at LCIS diagnosis
  • menopausal status
  • family history of breast cancer
  • finding LCIS in both breasts
  • also finding atypical hyperplasia (a benign breast disease) at the same time as LCIS
  • breast density

None of the 56 women who decided to have preventive bilateral mastectomy were diagnosed with breast cancer, though breast cancer was found in six of the women during preventive mastectomy surgery (three women had invasive breast cancer and three had DCIS).

If you’ve been diagnosed with LCIS, this study offers more information about how much your risk of breast cancer goes up because of that diagnosis. Depending on your unique situation and your preferences, you and your doctor may decide that you should undergo careful observation. You also may decide to use other strategies to reduce your risk, including taking hormonal therapy or preventive surgery. Together, you and your doctor can figure out the best plan for you.

For more information, visit the LCIS pages.

To connect with others who have been diagnosed with LCIS, visit the Discussion Board forum LCIS (Lobular Carcinoma In Situ).

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