Women with lobular carcinoma in situ (LCIS) showed a 2% annual risk of developing breast cancer, and women who chose chemoprevention reduced their annual cancer rate to less than 1%, in a single-center longitudinal study published online in Journal of Clinical Oncology.

LCIS is known to raise the risk of developing ductal carcinoma in situ or invasive carcinoma substantially, but estimates vary widely. In addition, no specific risk factors have been linked to disease progression. To determine the absolute risk of developing breast cancer over time and to explore the clinicopathological features that predispose patients to progression, researchers performed a longitudinal analysis of data concerning 1,060 patients diagnosed between 1980 and 2009 at Memorial Sloan Kettering Cancer Center, New York.

Most patients (831, 78%) chose to manage their condition with surveillance alone, 175 (17%) chose surveillance plus chemoprevention using a selective estrogen receptor modulator or an aromatase inhibitor, and the remaining 56 patients (5%) opted for bilateral prophylactic mastectomy. Overall, 150 of these women developed 168 breast cancers during a median follow-up of 81 months (range, 6-368 months), said Dr. Tari A. King and her associates at Memorial Sloan Kettering.

The annual incidence of breast cancer was 2% per year for the entire study population, with no indication that risk would plateau. Overall cumulative cancer incidence was 26%, similar to that reported in a National Surgical Adjuvant Breast and Bowel Project study. The use of chemoprevention was strongly associated with a reduction in breast cancer risk (HR, 0.27); the minority of women who chose this option reduced their annual cancer rate to less than 1%. This finding supports the current recommendation to use chemoprevention and highlights the significant impact of proper patient education and counseling, the researchers noted (J Clin Oncol. 2015 Sep 14. doi: 10.1200/JCO.2015.61.4743 ).

Unexpectedly, none of the clinicopathological features commonly thought to influence cancer risk – age at diagnosis, family history, breast density, menopausal status, presence of synchronous atypical hyperplasia, or presence of bilateral LCIS – were risk factors. Only tumor volume, as measured by the ratio of the number of slides with LCIS to the total number of slides available, was significantly greater in women whose disease progressed (0.5 to 1) than in women whose disease did not (0.3 to 1).

The National Cancer Institute, the Walsh Family Fund, and the Cary Grossman Breast Research Fellowship supported the study. Dr. King reported having no conflicts of interest; one of her associates reported receiving honoraria from Genomic Health.