29-Year Single-Center Longitudinal Experience Indicates 2% Annual Risk of Breast Cancer in Lobular Carcinoma in Situ


Key Points

  • The incidence of breast cancer was approximately 2% per year, with no evidence of a plateau.
  • Chemoprevention was associated with significantly reduced risk.

As reported by King et al in the Journal of Clinical Oncology, 29-year longitudinal experience at Memorial Sloan Kettering Cancer Center indicates an annual 2% risk of breast cancer in women with lobular carcinoma in situ. Risk was reduced with chemoprevention.

Study Details

The study involved 1,060 women with lobular carcinoma in situ without concurrent breast cancer treated between 1980 and 2009. Median age at lobular carcinoma in situ diagnosis was 50 years (range = 27–83 years); 56 patients (5%) underwent bilateral prophylactic mastectomy and 1,004 underwent surveillance with (n = 173) or without (n = 831) chemoprevention.

Breast Cancer Risk

At a median follow-up of 81 months (range = 6–368 months) among 1,032 women undergoing surveillance with or without chemoprevention, 150 developed 168 breast cancers (63% ipsilateral, 25% contralateral, 12% bilateral). Histology consisted of ductal carcinoma in situ (DCIS) in 35%, infiltrating ductal carcinoma in 29%, infiltrating lobular carcinoma in 27%, and other in 9%.

The annual incidence was 2% per year through the first 6 years after lobular carcinoma in situ diagnosis, with no evidence of a plateau out to 150 months. Cumulative incidence was 26% at 15 years. Median time to diagnosis was 50 months. Occult cancer was found in six (11%) of the patients who had undergone prophylactic mastectomy (three subcentimeter invasive carcinomas and three DCIS).

The 10-year cumulative risk of breast cancer was 7% in women receiving chemoprevention and 21% in those not receiving chemoprevention (P < .001). On multivariate analysis including age, mammographic density, and family history of breast cancer, only chemoprevention use was significantly associated with risk reduction (hazard ratio = 0.27, P ≤ .001). In a nested case-control analysis including 72 patient cases and 274 controls, higher volume of disease was associated with increased risk (P = .008).

The investigators concluded: “We observed a 2% annual incidence of breast cancer among women with [lobular carcinoma in situ]. Common clinical factors used for risk prediction, including age and family history, were not associated with breast cancer risk. The lower breast cancer incidence in women opting for chemoprevention highlights the potential for risk reduction in this population.”

Tari A. King, MD, of Memorial Sloan Kettering Cancer Center, is the corresponding author for the Journal of Clinical Oncology article.

The study was supported by the National Cancer Institute, Walsh Family Fund, and a Cary Grossman Breast Research Fellowship.

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