Risk of mortality by histologic type of breast cancer among women aged 50 to 79 years.

BACKGROUND: Recent studies suggest that the use of combined estrogen and progestin hormone replacement therapy is associated with an increased risk of invasive lobular carcinoma (ILC), but that it has little association with risk of invasive ductal carcinoma (IDC). Also, the incidence rates of ILC have risen over the past 10 years while those of IDC have remained constant. Differences in survival rates by histologic types of tumor have been reported, but few of the published studies were population based or had adequate power to address this issue. METHODS: We conducted a retrospective cohort study spanning the years 1974 through 1998 using data from the 9 cancer registries that have participated in the Surveillance, Epidemiology, and End Results Program since 1974. The cohort consisted of 164 958 women aged 50 to 79 years who had been diagnosed as having 1 of 7 histologic types of invasive breast cancer. Risks of mortality due to any cause were estimated using the Cox proportional hazards model. RESULTS: Women with ILC had a risk of mortality 11% lower than women with IDC. The magnitude of this difference has increased over the past 10 years and, from 1994 through 1998, the risk of mortality was 26% lower for women with ILC. Also, the risk of mortality was between 8% and 34% lower in women with mucinous carcinoma, comedocarcinoma, or medullary, tubular, and papillary carcinomas compared with women with IDC. CONCLUSIONS: Differences in prognosis by histologic type of breast cancer were identified. The survival rate of women 50 to 79 years old who have ILC, the cancer whose histologic type is the most closely linked with the use of combined estrogen and progestin hormone replacement therapy, is more favorable than that of women with IDC and appears to be improving over time.

Trends in incidence rates of invasive lobular and ductal breast carcinoma.

CONTEXT: Research has suggested that use of combined estrogen and progestin hormone replacement therapy (CHRT) increases breast cancer risk and that CHRT use is more strongly associated with the risk of invasive lobular breast carcinoma than that of invasive ductal carcinoma. Lobular carcinoma is less common than ductal carcinoma but can be more difficult to diagnose because of its subtle elusive infiltrative pattern. OBJECTIVE: To evaluate trends in invasive lobular and ductal carcinoma incidence rates from 1987 through 1999, during which time use of CHRT increased in the United States. DESIGN: Descriptive epidemiologic study. SETTING: Nine cancer registries that participate in the Surveillance, Epidemiology, and End Results (SEER) program of the National Cancer Institute and that cover Atlanta, Ga; Detroit, Mich; San Francisco-Oakland, Calif; Seattle, Wash; and Connecticut, Hawaii, Iowa, New Mexico, and Utah. POPULATION: Women 30 years of age and older residing in the areas covered by the 9 SEER registries. MAIN OUTCOME MEASURES: Proportional changes in incidence rates of invasive lobular and ductal carcinoma among women with no prior history of breast cancer. RESULTS: A total of 190 458 women were included in this analysis who were identified through the registries as having invasive breast cancer; 7682 of the 198 140 potentially eligible women (ie, those identified as not having in situ breast cancer) were excluded from this analysis because stage of cancer was unknown. Invasive breast cancer incidence rates adjusted for age and for SEER historic stage increased 1.04-fold (95% confidence interval [CI], 1.004-1.07) from 1987-1999 (206.7/100 000 to 214.1/100 000, age-adjusted). However, incidence rates of tumors classified as lobular increased 1.52-fold (95% CI, 1.42-1.63), and those classified as mixed ductal-lobular increased 1.96-fold (95% CI, 1.80-2.14); rates of these types combined increased 1.65-fold (95% CI, 1.55-1.78) (19.8/100 000 to 33.4/100 000, age-adjusted). In contrast, ductal carcinoma rates remained largely constant (153.8/100 000 to 155.3/100 000, age-adjusted; proportional change, 1.03 [95% CI, 0.99-1.06]). The proportion of breast cancers with a lobular component increased from 9.5% in 1987 to 15.6% in 1999. CONCLUSIONS: Ductal carcinoma incidence rates remained essentially constant from 1987-1999 while lobular carcinoma rates increased steadily. This increase presents a clinical challenge given that lobular carcinoma is more difficult to detect than ductal carcinoma by both physical examination and mammography.

Changing incidence of lobular carcinoma in situ of the breast.

Estimating the incidence of lobular carcinoma in situ (LCIS) of the breast is challenging because it lacks both clinical and mammographic signs and is usually an incidental finding in breast biopsies performed for other reasons. In general, population-based studies are believed to provide the most accurate measures, but few documenting changes in LCIS incidence rates over time have been reported. Age-adjusted age-specific LCIS incidence rates among women with no prior history of in situ or invasive breast carcinoma from 1978 to 1998 were obtained from nine population-based cancer registries that participate in the Surveillance, Epidemiology, and End Results (SEER) Program. Linear trends were evaluated using negative binomial regression. Overall, LCIS incidence rates increased fourfold (95% confidence interval, 2.9-5.6) over the study period. Specifically, they rose from 0.90/100,000 person-years in 1978-80 to 2.83/100,000 person-years in 1987-89, but then increased only modestly up to 1996-98 where the incidence rate was 3.19/100,000 person-years. However, among women 50-79 years of age, LCIS incidence rates increased continuously over the study's duration. In 1996-98, 50-59 year-olds had the highest incidence rate (11.47/100,000 person-years) and experienced the greatest absolute increase in incidence over the study period (9.48/100,000 person-years). LCIS incidence rates have steadily increased from 1978 to 1998 only among postmenopausal women. Further research is required to assess what factors are contributing to these trends.