Stage Shifting by Modifying the Determinants of Breast Cancer Stage at Diagnosis: A Simulation Study.

Simple Summary: The impact of breast cancer on individuals and in populations can be reduced if the cancer is detected in an early stage of disease as treatments are generally less harsh and more successful. Knowing which factors to modify and by what amount that could shift breast cancer diagnoses to early stages of disease were studied in this project. Factors related to stage at diagnosis in a previous analysis of women diagnosed with breast cancer were assessed using data that mimicked the real data. The proportions of modifiable lifestyle factors in a population were increased or decreased, such as those ever having a mammogram, to see the effect on detecting more cancers in the earliest stages. Similarly, the average amounts of protein eaten per day or calories consumed were also increased and decreased. Increasing the total amount of protein eaten per day by even just 5 grams was the most important factor found in this study to improve early breast cancer diagnoses. The findings from this study could be helpful in breast cancer prevention programs that could target key modifiable factors and by other researchers studying other types of cancer. Background: Breast cancer is the most common cancer in Canadian women; nearly 25% of women diagnosed with cancer have breast cancer. The early detection of breast cancer is a major challenge because tumours often grow without causing symptom. The diagnosis of breast cancer at an early stage (stages I and II) improves survival outcomes because treatments are more effective and better tolerated. To better inform the prevention of and screening for breast cancer, simulations using modifiable rather than non-modifiable risk factors may be helpful in shifting the stage at diagnosis downward. Methods: Breast cancer stages were simulated using the data distributions from Alberta's Tomorrow Project participants who developed breast cancer. Using multivariable partial proportional odds regression models, modifiable lifestyle factors associated with the stage of cancer at diagnosis were evaluated. The proportions or mean levels of these lifestyle factors in the simulated population were systematically changed, then multiplied by their corresponding estimated odds ratios from the real data example. The effects of these changes were evaluated singly as well as cumulatively. Results: Increasing total dietary protein (g/day) intake was the single most important lifestyle factor in shifting the breast cancer stage downwards followed by decreasing total dietary energy intake (kcal/day). Increasing the proportion of women who spend time in the sun between 11 am and 4 pm in the summer months, who have had a mammogram, who have been pregnant or reducing the proportion who are in stressful situations had much smaller effects. The percentage of Stage I diagnoses could be increased by approximately 12% with small modifications of these lifestyle factors. Conclusion: Shifting the breast cancer stage at diagnosis of a population may be achieved through changes to lifestyle factors. This proof of principle study that evaluated multiple factors associated with the stage at diagnosis in a population can be expanded to other cancers as well, providing opportunities for cancer prevention programs to target specific factors and identify populations at higher risk. [ABSTRACT FROM AUTHOR]