Abstract A80: Disparity in breast cancer incidence and mortality among rural counties in central Pennsylvania

Background: The state of PA with the age adjusted annual breast cancer mortality rate of 27/100,000 ranks the 13^th among all states. Stratification of breast cancer incidence and mortality data of the state by its counties classifies a total of 11 counties, of which 6 are within its central rural region, as significantly above the national average. These 6 counties are adjacent to counties, within the same rural region, that have below or at the national average for breast cancer incidence and mortality. Under utilization of screening mammography by women in rural areas, compared with those in urban settings, has been associated to the differences in breast cancer mortality between rural and urban areas; however, it is unlikely that differences in mammography utilization or access to health services can fully explain the observed disparity in breast cancer incidence and mortality among rural counties. We have implemented an exploratory project to discern reasons for this disparity among counties in central PA.

Methods: This study exploits the case-control design, where cases are identified as women from counties with above the national average for breast cancer mortality, and the control group constitutes women from counties below the national average. Women, diagnosed with their first primary invasive carcinoma between January 1, 2001 and December 31, 2007, were identified from the cancer registry at the Geisinger Health System (GHS). Date of surgery was considered as the date of diagnosis. Estrogen receptor (ER) and progesterone receptor (PR) and HER2/neu status were dichotomized as positive and negative. Due to small number of women diagnosed with TNM stages III and IV, this variable was dichotomized into less advanced (stages I and II) and advanced (stages III and IV). Histologic grade were categorized as 1–3. Breast cancer phenotypes were classified based on the status of ER, PR and HER2/neu as “ER⁺ and/or PR⁺, HER2⁻” “ER⁺ and/or PR⁺, HER2⁺”, “ER⁻/PR⁻, HER2⁺” or “ER⁻/PR⁻, HER2⁻”.

Results: So far pathologic data have been retrieved for 115 controls and 91 cases. The mean age at the time of diagnosis for cases and controls were 69 (±12) and 68 (±12), respectively. About 14.7% of controls and 10.5% of cases were diagnosed with more advanced stages (OR= 1.4, 95% CI 0.67–2.90); A higher proportion of controls were diagnosed with poorly differentiated histologic grade (23.9% vs. 20.7%). Prevalence of HER2/neu positive breast cancer was 7.9% and 6.2% in cases and controls, respectively (OR= 0.79, 95% CI 0.29–2.20). Similarly, prevalence of ER negative breast cancer was slightly higher in cases than controls (13.7% vs. 11.2%, OR= 0.82, 95% CI 0.40–1.68). In contrast, prevalence of PR negative breast cancer was higher in controls than in cases (26% vs. 19%, OR=1.36, 95% CI 0.81–2.29). The prevalence of different subtypes of breast cancer did not differ between cases and controls.

Conclusions: Preliminary findings from this ongoing study suggest no statistically significant differences in the prevalence of pathologic prognostic indicators at the initial clinical presentation of the disease between women from counties with the above the national average mortality rate and those in counties with below the national average. The relative effect of other contributing factors i.e. existing comorbid conditions, and/or compliance with adjuvant therapy are also being evaluated.