A researcher used SEER data to calculate an estimate of the number of women with breast cancer in Iowa on a certain date. This estimate is:

The estimate in question refers specifically to the number of women with breast cancer in Iowa on a certain date, which relates to the concept of prevalence. Prevalence is defined as the total number of cases of a disease (in this instance, breast cancer) within a population at a specific point in time. It gives an understanding of how widespread the disease is within that population at that moment.

In the context of the question, using SEER (Surveillance, Epidemiology, and End Results) data to arrive at an estimate indicates that the researcher is assessing existing cases of breast cancer among women in Iowa, not new cases or deaths associated with the disease. Therefore, this aligns perfectly with the definition of prevalence, focusing on the total cases rather than those diagnosed (incidence) or those leading to death (mortality).

Age-adjusted rates, while useful in comparing disease rates across populations, are not relevant in this context as they adjust the prevalence or incidence figures for age distributions, rather than providing a direct estimate of existing cases at a specific time. Incidence would refer to the number of new cases diagnosed over a specific period rather than the total cases at a single point, and mortality relates to deaths due to the disease, which is not what