Abstract 5499: A descriptive epidemiological study of lobular carcinoma of the breast and the effects of normal lobular regression at menopause

Abstract

Abstract Background: Lobular carcinoma (LC) is a distinctive neoplasm originating in the milk producing glands and constituting about 12% of all breast cancer cases. LC differs from the more common invasive ductal carcinoma (IDC) by morphology and biology. We report the results of a descriptive epidemiological study of LC and a comparison of the pathogenesis of lobular and ductal carcinoma of the breast. Methods: A total of 86,846 cases of invasive LC (ILC) from women, aged 20 to 85, were obtained from NCI's SEER Program for the years 1973-2008 in the United States. There were 20,512 cases of LC in-situ (LCIS) and 66,634 cases of ILC. For comparison, 692,201 cases of IDC and 61,569 cases of ductal carcinoma in situ (DCIS) were collected. The analysis compared trends, age specific rates, log-log plots, age frequencies and relative survival rates. Results: From 1973-2008, the age-adjusted rate of LC progressively increased from 5.8 to 16.4/ 100,000 women. In an age frequency analysis of age versus rate, LCIS increased to 0.22/ 100,000 women at age 50, and then declined to 0.02/100,000 women at age 80. ILC increased to 0.11/100,000 women at age 50, and then plateaued after menopause but did not decline. Log-log plots revealed parallel curves between ILC and IDC in both pre-menopausal and post-menopausal age groups. At age 50, the age specific rate of LCIS increased to 11.3/100,000 women then progressively decreased. In contrast, the age specific rate of DCIS was 22.1/100,000 women at age 50 and continued to increase after menopause. Conclusions: At menopause, the incidence of LCIS decreases as a result of lobular involution of the breast. In contrast, DCIS continues to increase. ILC does not decline but plateaus suggesting that the initiation of ILC occurs before menopause, but the tumor becomes clinically apparent only after menopause. Although morphologically different, parallel log-log plots of age specific rates and age frequency analysis suggest a similar pathogenesis for IDC and ILC even though epidemiological patterns are different. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5499. doi:1538-7445.AM2012-5499